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Chrononutrition and the Temporal Dimension of Metabolic Health Across the Aging Lifespan

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dr Karunia Valeriani Japar

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Keywords: Chrononutrition, Circadian Rhythm, Healthy Aging, Metabolic Health, Time-Restricted Eating

Synchronizing Metabolism with the Biological Clock

Human metabolism operates within a finely tuned temporal framework orchestrated by circadian rhythms, endogenous, near 24-hour biological cycles that regulate behavioral and physiological processes in anticipation of environmental changes. The alignment between these intrinsic rhythms and external cues, such as the light-dark cycle and feeding-fasting patterns, is essential for metabolic homeostasis. Chrononutrition, an emerging field within nutritional science, explores the intricate interplay between the timing of food intake and circadian biology. It posits that “when” we eat may be just as influential as “what” and “how much” we eat in determining metabolic outcomes.

Over the past few decades, the global rise in obesity, insulin resistance, and metabolic syndrome has underscored the limitation of conventional dietary approaches focusing solely on caloric restriction or macronutrient composition. Increasing evidence suggests that circadian disruption, whether induced by shift work, irregular eating schedules, or chronic exposure to artificial light plays a pivotal role in the pathogenesis of metabolic disorders. Misalignment between internal circadian clocks and external behaviors disrupts glucose homeostasis, impairs lipid oxidation, and alters appetite-regulating hormones, thereby predisposing individuals to weight gain and systemic inflammation. These effects are further compounded by aging, during which circadian amplitude diminishes, leading to reduced metabolic flexibility and resilience.

Emerging research has begun to redefine nutrition through the temporal lens of circadian biology. Experimental and clinical studies demonstrate that aligning food intake with the body’s endogenous rhythms, particularly through restricted feeding windows or daytime eating can enhance insulin sensitivity, improve energy efficiency, and support mitochondrial function. This paradigm shift introduces timing as a critical dimension in preventive metabolic medicine and longevity science. Understanding and manipulating the synchronization between nutrient intake and biological clock mechanism may provide a novel, non-pharmacological strategy to restore metabolic health across the lifespan.

The objective of this review is to examine the scientific foundations and clinical implications of chrononutrition. By exploring how temporal patterns of eating modulate circadian rhythms, energy metabolism, and aging processes, we aim to integrate emerging mechanistic insights into practical frameworks for metabolic wellness and healthy longevity.

Circadian Rhythms and Metabolic Regulation

The mammalian circadian timing system comprises a hierarchical network of molecular clocks that operate with near-24-hour periodicity to coordinate physiological processes with environmental cycles. The central pacemaker located in the suprachiasmatic nucleus (SCN) of the anterior hypothalamus receives photic input via the retinohypothalamic tract and serves as the master regulator of systemic circadian rhythms, synchronizing peripheral oscillators in metabolically active organs such as the liver, skeletal muscle, adipose tissue, pancreas, and gastrointestinal tract to maintain energy homeostasis and metabolic efficiency [1,2].

Figure 1. Multiorgan distribution of peripheral circadian clocks and their physiological functions [2]

Synchronization of these distributed clocks depends on external time cues, or zeitgebers, which entrain circadian rhythms to the 24-hour light–dark and feeding–fasting cycles. Light is the primary zeitgeber for the SCN, whereas peripheral clocks are particularly sensitive to meal timing and metabolic signals, allowing feeding schedules to phase-shift hepatic and other tissue clocks, sometimes independently of the central pacemaker. Hormonal rhythms act as additional systemic synchronizers: diurnal oscillations in cortisol, melatonin, insulin, GLP-1, leptin, and ghrelin convey temporal information to metabolic tissues, so that mistimed food intake during the biological night, when melatonin is high and insulin responsiveness is reduced, impair glucose tolerance and promotes adverse metabolic profiles [2,3,4,5].

At the molecular level, circadian rhythmicity is generated by interlocking transcription–translation feedback loops involving core clock genes such as CLOCK and BMAL1 which drive the expression of PER and CRY genes; the PER/CRY complexes then inhibit CLOCK–BMAL1 activity, producing self-sustained oscillations with roughly 24-hour periodicity. These clock mechanisms regulate a large fraction of the metabolic transcriptome across tissues, controlling pathways related to glucose and lipid metabolism, mitochondrial biogenesis, and redox balance; disruption of core clock components or desynchrony between central and peripheral clocks leads to insulin resistance, dyslipidemia, hepatic steatosis, and accelerated metabolic disease, whereas maintaining alignment between brain and liver clocks appears protective against chrono-metabolic disorders [6,7,8].

The metabolic response to food intake extends beyond caloric content and macronutrient composition to encompass a critical temporal dimension regulated by circadian biology. Meal timing influences multiple interconnected physiological processes, including glycemic regulation, lipid metabolism, energy expenditure, and cellular bioenergetics. Accumulating evidence demonstrates that consuming nutrients at circadian-appropriate times optimizes metabolic efficiency, whereas mistimed eating, particularly during the biological night disrupts metabolic homeostasis and promotes adverse cardiometabolic outcomes.

Glycemic control exhibits pronounced circadian variation, with superior glucose tolerance and insulin sensitivity observed during the biological morning compared to the evening. This diurnal pattern reflects coordinated circadian regulation of pancreatic β-cell insulin secretion, peripheral tissue insulin responsiveness, and hepatic glucose production. When identical test meals are administered at different times of day, postprandial glucose excursions are consistently 17% higher in the evening (approximately 8:00 PM) than in the morning (8:00 AM), independent of behavioural cycle effects. The mechanisms underlying this temporal variation are multifactorial: morning insulin sensitivity peaks coincide with maximal expression and membrane recruitment of GLUT4 in skeletal muscle, enhanced insulin receptor signaling, and greater first-phase insulin secretion from pancreatic islets. Conversely, evening meals elicit blunted early-phase insulin responses (27% lower) yet require 14% higher late-phase insulin secretion to achieve inferior glycemic control, suggesting both impaired β-cell function and decreased insulin sensitivity during the biological evening. Late-night eating compounds these effects by occurring during periods of elevated melatonin secretion, which directly inhibits insulin release and further impairs glucose tolerance [9,10,11,12,13,14,15].

Lipid metabolism similarly displays circadian rhythmicity that profoundly influences postprandial triglyceride handling and substrate oxidation. Postprandial triglyceride responses to identical high-fat meals are approximately 2-fold higher following breakfast compared to lunch, and nighttime eating (1:30 AM) produces more pronounced and prolonged triglyceride elevation that daytime consumption (1:30 PM). These temporal differences arise from circadian variation in intestinal lipid absorption, hepatic triglyceride assembly and secretion, and peripheral tissue lipid uptake and oxidation. At the molecular level, clock genes regulate rhythmic expression of key lipogenic enzymes, including sterol regulatory element-binding protein-1c (SREBP-1c), acetyl-CoA carboxylase (ACC), and fatty acid synthase, which peak during feeding periods to coordinate lipid biosynthesis with nutrient availability. Conversely, lipolytic gene expression and adipose tissue lipid mobilization are enhanced during fasting periods. Importantly, substrate oxidation patterns shift dramatically across the 24-hour cycle: carbohydrate oxidation is highest during the biological morning (~12 hours prior to dim light melatonin onset), whereas fat oxidation peaks during the biological evening and nocturnal fasting period. Late-evening eating disrupts this metabolic switch by maintaining carbohydrate catabolism during sleep initiation, thereby delaying the transition to lipid oxidation and reducing 24-hour fat utilization. This disruption persists for several hours into the sleep episode, promoting lipid accumulation and positive energy balance [16,17,18,19,20].

Thermogenesis and energy expenditure also exhibit circadian control that modulates the metabolic impact of food intake timing. Diet-induced thermogenesis (DIT), the increase in energy expenditure following meal consumption is significantly greater in response to morning meals compared to isocaloric evening meals, with some studies reporting DIT values twice as high during the biological morning. This temporal variation reflects circadian regulation of sympathetic nervous system activity, brown adipose tissue thermogenic gene expression (particularly uncoupling protein 1, UCP1), and basal metabolic rate, all of which peak during the active phase. Time-restricted feeding paradigms that confine food intake to the early active phase enhance brown adipose tissue thermogenesis and increase expression of thermogenic genes (UCP1 and PGC-1a), contributing to improved metabolic outcomes independent of caloric restriction [20,21,22].

At the cellular level, the metabolic consequences of meal timing are mediated through nutrient-sensitive signalling pathways that interface with circadian clock machinery, particularly the AMPK-NAD+-sirtuin axis. During fasting periods, declining ATP levels and increasing AMP concentrations activate AMPK, which phosphorylates and inhibits acetyl-CoA carboxylase, thereby relieving malonyl-CoA-mediated suppression of carnitine palmitoyltransferatse 1 (CPT1) and promoting mitochondrial fatty acid b-oxidation. Simultaneously, fasting elevates the NAD+/NADH ratio, which activates sirtuin deacetylases, particularly SIRT1 in the nucleus and SIRT3 in mitochondria. SIRT1 deacetylates mitochondrial metabolic enzymes involved in the TCA cycle, fatty acid b-oxidation. Simultaneously, fating elevates NAD+ /NADH ratio, which activates sirtuin deacetylases, particularly SIRT1 in the nucleus and SIRT3 in mitochondria. SIRT1 deacetylates and activates PGC-1α and FOXO1, key transcriptional regulators that upregulate mitochondrial biogenesis, fatty acid oxidation genes, and gluconeogenic enzymes. SIRT3 deacetylates mitochondrial metabolic enzymes involved in the TCA cycle, fatty acid β-oxidation, and electron transport chain, thereby enhancing mitochondrial respiratory efficiency and ATP production while reducing oxidative stress. This integrated AMPK-sirtuin response requires functional circadian clock components; AMPK-deficient mice fail to activate SIRT1 and exhibit impaired PGC-1α deacetylation, blunted mitochondrial gene induction, and metabolic inflexibility during fasting and exercise. Critically, AMPK activation itself exhibits circadian rhythmicity, and the fasting-induced increase in NAD⁺ levels, which drives SIRT1 activity is abolished in circadian clock-disrupted animals that cannot shift between metabolic substrates. Conversely, feeding activates nutrient-sensing pathways including mTOR and insulin signalling, which promote anabolic processes and suppress AMPK-SIRT1 signalling. Late-night eating inappropriately activates these anabolic pathways during the biological night when the body is primed for fasting-associated catabolism and cellular repair, thereby disrupting the temporal coordination between nutrient-sensing pathways and circadian phase [23,24,25,26,27].

The concept of chronokinetics, the time of the day dependent variation in nutrient absorption, distribution, metabolism, and excretion provides an integrative framework for understanding these phenomena. Peptide and amino acid transporters such as PEPT1 (H⁺-coupled oligopeptide transporter) and LAT4 (basolateral neutral amino acid transporter) display peak expression and activity during the early active phase, coinciding with enhanced absorption of dipeptides and branched-chain amino acids. Glucose transporter expression and intestinal glucose uptake similarly peak before the active period. For lipids, microsomal triglyceride transfer protein (MTP), the rate-limiting enzyme for intestinal lipoprotein assembly shows diurnal variation inversely related to the clock-controlled repressor small heterodimer partner (SHP), with peak lipid absorption occurring during the active phase. This temporal coordination of nutrient absorption with metabolic processing capacity ensures that nutrients arrive in the circulation when tissues are metabolically primed for their utilization. Clock gene disruption abolishes these rhythms; for example, Clock-mutant mice exhibit continuously elevated intestinal lipoprotein production at all times, losing the normal nadirs seen after meals, which contributes to hyperlipidemia and atherosclerosis. Human metabolomic studies confirm these principles: postprandial blood levels of 16 amino acids, including arginine and leucine are significantly higher following morning meals compared to evening meals despite identical meal composition reflecting circadian differences in intestinal absorption, hepatic first-pass metabolism, and peripheral tissue uptake [10,16].

Collectively, these mechanistic insights establish that meal timing functions as a powerful modulator of metabolic health by determining whether nutrient intake aligns with or opposes endogenous circadian metabolic rhythms. Consuming the majority of calories during the biological day, when insulin sensitivity is maximal, thermogenesis is elevated, and metabolic machinery is optimized for nutrient processing, promotes metabolic efficiency and prevents metabolic disease. Conversely, late-night eating during periods of reduced insulin sensitivity, elevated melatonin,  suppressed thermogenesis, and cellular programs oriented toward fasting and repair creates metabolic stress that contributes to glucose intolerance, dyslipidemia, obesity, and cardiometabolic disease.

Clinical Evidence: Time-Restricted Feeding and Circadian interventions

Clinical evidence from both human and animal studies indicates that aligning food intake with circadian biology through early time-restricted feeding (eTRF) and related time-restricted eating (TRE) protocols exerts favorable effects on multiple cardiometabolic outcomes, often independent of weight loss. In one of the first rigorously controlled human trials, five weeks of eTRF (6-h eating window ending mid-afternoon) in men with prediabetes improved insulin sensitivity, reduced fasting insulin and β-cell workload, and lowered systolic and diastolic blood pressure by approximately 10–11 mmHg without changes in body weight, suggesting direct circadian and hormonal mechanisms rather than simple caloric effects. Subsequent randomized trials and reviews of TRE in metabolic syndrome and at-risk populations show that restricting eating to an 8–10 h window earlier in the day improves glycemic control, fasting glucose, LDL cholesterol, and markers of oxidative stress and inflammation, and can also enhance subjective sleep quality and daytime alertness when the window is aligned with the biological day [28,29,30,31].

Interventional and mechanistic studies consistently highlight that the timing of the eating window rather than time restriction alone determines whether TRE is metabolically beneficial or detrimental. Early time-restricted eating, in which most calories are consumed in the morning and early afternoon, capitalizes on peak insulin sensitivity, higher diet-induced thermogenesis, and favourable incretin and cortisol profiles, leading to greater improvements in fasting glucose, HOMA-IR, and blood pressure compared with mid-day or late-day windows of similar duration. In contrast, protocols that cluster food intake in the evening or night are associated with higher body weight and fat mass, poorer glycemic control, and adverse changes in lipid profile, emphasizing that circadian alignment, eating during the biological active phase is essential for TRE to exert protective metabolic effects [32,33,34].

Experimental models of circadian misalignment provide insight into the mechanisms by which late eating and shift-work patterns impair metabolic health. Laboratory “forced desynchrony” protocols that decouple behavioural cycles from the endogenous circadian system demonstrate that eating and sleeping at inappropriate circadian phases acutely reduce glucose tolerance, lower insulin sensitivity, increase blood pressure, and decrease leptin, changes that would promote weight gain and cardiometabolic risk if sustained. Epidemiological data in shift workers mirror these findings: chronic exposure to irregular schedules and nocturnal eating is associated with higher prevalence of obesity, type 2 diabetes, and cardiovascular disease, supporting the concept that circadian misalignment acts as an independent metabolic stressor beyond sleep loss and diet quality alone [35,36,37].

Comparative trials directly contrasting early versus late eating windows underscore the importance of meal timing for glucose metabolism and body composition. In a randomized trial in healthy adults, five weeks of eTRF (e.g., 8:00–14:00) improved insulin sensitivity and reduced fasting glucose and body mass, whereas a mid-day or later TRE schedule of the same duration did not elicit comparable benefits, despite similar caloric intake. Reviews of TRE in metabolic syndrome similarly report that early or circadian-aligned windows are more likely to reduce body fat, diastolic blood pressure, and fasting glucose than late windows, while evening-focused eating is linked to increased adiposity and higher glycemic levels. Taken together, these data support the view that TRE and eTRF represent promising, low-cost interventions for cardiometabolic and sleep health, provided that feeding windows are shifted toward the earlier part of the day and synchronized with endogenous circadian rhythms [30,32,38,39].

Chrononutrition in Aging and Longevity

Aging is characterized by progressive deterioration of circadian rhythm function, manifesting as reduced amplitude of oscillations, phase shifts, increased fragmentation, and desynchronization between central and peripheral clocks. These age-related circadian disruptions contribute directly to metabolic dysfunction across multiple organ systems. In the suprachiasmatic nucleus (SCN), the master circadian pacemaker, neuronal firing rates decline by more than 50% with age, impairing the synchronization capacity of the central clock and its ability to coordinate peripheral oscillators in metabolically active tissues such as the liver, skeletal muscle, adipose tissue and pancreatic islets. At the peripheral level, approximately 45% of rhythmically expressed genes in the liver of aged mice lose their circadian pattern, particularly those involved in glycerol and sterol metabolism, while adipose tissue exhibits diminished rhythmicity in genes regulating lipid metabolism, glucose transport, and thermogenesis. Human studies corroborate these findings, demonstrating that healthy middle-aged adults display significantly reduced circadian amplitude in plasma lipid profiles, earlier acrophase (peak timing), and altered phase relationships between centrally controlled markers such as melatonin and peripheral metabolic outputs compared to younger individuals. This progressive weakening of circadian robustness with age creates a state of “systemic time-fragility,” wherein the organism’s capacity to maintain metabolic homeostasis and adapt to environmental stressors is profoundly compromised [40,41,42].

The molecular mechanisms underlying age-related circadian decline involve interconnected pathways centered on telomere homeostasis, sirtuin-mediated epigenetic regulation, and NAD⁺ metabolism. Telomeres, protective nucleoprotein structures at chromosome ends exhibit circadian rhythmicity in their associated RNA (TERRA) and histone modifications (H3K9me3), a pattern governed by the core clock transcription factor BMAL1. With aging, this circadian regulation of telomeric heterochromatin is lost, leading to accelerated telomere attrition, cellular senescence, and metabolic disease susceptibility. SIRT1, an NAD⁺-dependent deacetylase with pleiotropic anti-aging properties, functions as a critical integrator of circadian and metabolic signaling. SIRT1 deacetylates PER2 and BMAL1 to enhance circadian amplitude and stability; deficiency of SIRT1 in the SCN of aged mice results in disrupted activity rhythms, prolonged intrinsic periods, and impaired light entrainment, phenotypes that are recapitulated in young mice with brain-specific SIRT1 deletion. Conversely, increasing SIRT1 expression mitigates these age-related circadian impairments and extends telomere length through c-Myc-dependent activation of telomerase reverse transcriptase (TERT). The activity of SIRT1 is intimately linked to cellular NAD⁺ levels, which themselves exhibit circadian oscillations driven by the clock-controlled enzyme nicotinamide phosphoribosyltransferase (NAMPT). Aging-associated systemic NAD⁺ depletion impairs hypothalamic function and disrupts the reciprocal regulation between SIRT1 and clock genes, culminating in metabolic pathologies including obesity, insulin resistance, and chronic inflammation. Administration of NAD⁺ precursors such as nicotinamide riboside in aged mice restores BMAL1 chromatin binding, normalizes circadian gene expression oscillations, enhances mitochondrial respiration, and reestablishes nocturnal activity patterns to youthful levels, demonstrating the therapeutic potential of targeting NAD⁺-sirtuin-clock axis in combating age-related circadian and metabolic decline [40].

Interventions that restore circadian robustness represent promising strategies for promoting healthy aging and longevity. Time-restricted feeding (TRF), in which food intake is confined to a consistent, shortened window aligned with the active phase has emerged as a potent non-pharmacological approach to reinforce circadian rhythms and improve metabolic outcomes in aged organisms. In Drosophila, intermittent time-restricted feeding (iTRF) with night-specific fasting significantly extends both lifespan and health span through circadian-dependent activation of autophagy; genetic disruption of clock genes abolishes iTRF-mediated longevity benefits, demonstrating an absolute requirement for functional circadian machinery. The autophagy genes Atg1 and Atg8a are circadian-regulated with peak expression during the nighttime fasting period, and iTRF enhances their expression in a clock-dependent manner. Critically, night-specific upregulation of autophagy is both necessary and sufficient for lifespan extension: temporal knockdown of autophagy genes specifically during the night eliminates iTRF benefits, while night-specific overexpression of these genes extends lifespan to the same degree as iTRF even under ad libitum feeding conditions. By contrast, day-specific fasting or autophagy induction fails to confer longevity benefits, highlighting the importance of temporal alignment between nutrient restriction and endogenous circadian programs. In mammalian models, TRF during the active phase (dark period) restores metabolic oscillations and clock gene expression in peripheral tissues of aging mice, improves glucose tolerance and insulin sensitivity, enhances brown adipose tissue thermogenesis and expression of mitochondrial biogenesis genes (UCP1, PGC-1α), and counters age-related behavioural and metabolic phenotypes. These effects are independent of caloric restriction and insulin signalling pathways, suggesting that TRF operates through distinct circadian-autophagy mechanisms that can be combined with traditional anti-aging interventions such as dietary restriction for synergistic benefits [40,43,44].

Beyond nutrient timing, other circadian interventions show promise for mitigating age-related rhythm deterioration. Timed light exposure acts as a powerful zeitgeber that can realign central clock phase and amplitude, while scheduled physical exercise functions as a non-photic entrainment signal capable of strengthening circadian oscillations in both central and peripheral tissues. In mice, scheduled voluntary wheel running preserves high-amplitude SCN clock gene oscillations under constant darkness conditions, prevents progressive rhythm damping, and maintains temporal coordination between the SCN and peripheral clocks effects characteristics of exercise of bona fide non-photic zeitgeber. Exercise remodels SCN network coupling by reducing GABAergic inhibition, increases synchrony and amplitude of PER1 and PER2 gene rhythms, and restores robust behavioral rhythms in mice with impaired circadian signaling. In humans, exercise exhibits time-of-day-dependent phase-shifting effects: morning exercise delays circadian phase (advancing melatonin onset), while evening exercise advances phase (delaying melatonin onset), providing a theoretical basis for personalized chronotherapeutic exercise prescriptions to correct phase misalignment disorders prevalent in aging populations. Combined interventions incorporating timed feeding, strategic light exposure, and scheduled physical activity may synergistically reinforce circadian amplitude and entrainment, thereby promoting metabolic health and cognitive function throughout the aging process [45].

The convergence of chrononutrition principles with established longevity pathways offers a mechanistic framework for understanding how temporal eating patterns promote healthy aging. Reduced activity of nutrient-sensing pathways including mTOR-S6K and insulin-IGF-1 signalling, extends longevity across species from yeast to mammals, and both caloric restriction (CR) and fasting paradigms exert anti-aging effects through inhibition of mTOR, activation of AMPK and sirtuins, enhancement of mitochondrial respiration, and induction of autophagy. Importantly, these nutrient-sensing pathways exhibit circadian regulation and are differentially modulated by meal timing: feeding during the active phase suppresses mTOR transiently and in phase with circadian rhythms, whereas late-night eating inappropriately activates anabolic mTOR signalling during periods when the organism is primed for catabolic processes and cellular repair. Fasting periods elevate the cellular NAD⁺/NADH ratio, activating SIRT1 and SIRT3 to deacetylate and activate transcriptional regulators (PGC-1α, FOXO1) and mitochondrial enzymes involved in fatty acid oxidation, the TCA cycle, and electron transport, thereby enhancing metabolic flexibility and stress resistance. Time-restricted feeding that aligns fasting windows with the biological night capitalizes on these endogenous circadian-metabolic programs, amplifying autophagy induction, mitochondrial quality control, and cellular stress responses at circadian phases when they are most effective. This temporal coordination distinguishes chrononutrition from conventional caloric restriction: while CR reduces total energy intake, TR optimizes when energy is relative to the circadian system, producing metabolic benefits even without caloric deficit. The independence yet complementarity of these approaches suggests that combining chrononutrition strategies (early TRF aligned with active phase) with moderate caloric restriction and circadian entrainment cues (light, exercise) may yield additive or synergistic effects on longevity pathways, offering a multifaceted intervention to promote healthy aging and extend health span [21,24,43,44,46,47,48].

Translational and Clinical Applications

Chrononutrition is increasingly recognized as a practical and scalable lifestyle intervention that can be embedded into routine care in metabolic and cardiometabolic clinics. By focusing on when patients eat rather than only what or how much, clinicians can leverage circadian biology to improve glycemic control, weight regulation and cardiometabolic risk with relatively low behavioural complexity. Clinical reviews and emerging trials indicate that structured time-restricted eating (TRE) or time-restricted feeding (TRF), especially with earlier daytime eating windows and prolonged nocturnal fasting, can reduce body weight and fat mass, improve fasting glucose and sometimes lipid profiles, and support blood pressure control when aligned with the biological day. These findings support the incorporation of chrononutrition into lifestyle prescriptions for obesity, metabolic syndrome, prediabetes, and type 2 diabetes, alongside conventional dietary counselling and physical activity promotion [5,15,49].

Integration of chrononutrition into clinical workflows is being enabled by continuous glucose monitoring (CGM), wearable-derived circadian data, and AI-driven decision support. CGM captures 24‑hour glucose excursions that can be directly linked to clock time and feeding–fasting patterns, allowing clinicians to visualize how late eating, irregular meal timing, or short nocturnal fasts worsen glycemic variability and dawn phenomenon. Wearables that track sleep–wake cycles, physical activity, heart rate, and sometimes light exposure can be used to infer chronotype and circadian alignment, providing a substrate for tailoring eating windows to an individual’s biological day rather than clock time alone. AI-powered precision nutrition platforms now integrate CGM, microbiome, and lifestyle data to generate personalized dietary and meal-timing recommendations, demonstrating improved metabolic responses and scalability compared with heuristic counselling in early implementations [50,51,52,53,54,55,56].

From a practical standpoint, clinic-friendly chrononutrition protocols typically emphasize: (1) advancing the main caloric load to the morning and early afternoon; (2) extending the overnight fasting interval; and (3) maintaining day-to-day regularity in meal timing to minimize “eating jetlag.” Common starting protocols include a 10‑hour daytime window (e.g., 08:00–18:00) or 8‑hour window (e.g., 08:00–16:00), with ≥12–16 hours of nightly fasting, adjusted for chronotype, medication regimens, and comorbidities such as insulin-treated diabetes. Clinical guidance often prioritizes: a substantial breakfast within 1–2 hours of waking; front-loading protein and complex carbohydrates earlier in the day; avoiding large meals within 3 hours of habitual bedtime; and using CGM or capillary glucose to iteratively refine meal timing based on postprandial responses and nocturnal glycemia. To support real-world adherence, protocols are typically implemented on ≥5–6 days per week rather than demanding rigid daily adherence, with built-in flexibility for social or cultural events [5,15,49,52,53].

Digital health and precision nutrition platforms play a central role in sustaining engagement and operationalizing chrononutrition at scale. Smartphone applications integrated with CGM, wearables, and digital food logs can provide real-time feedback on eating windows, nocturnal fasting duration, and alignment between meal timing, sleep, and activity, using simple visualizations and nudges to reinforce earlier eating. AI-enhanced systems can translate complex biosensor streams into actionable, personalized prompts, such as recommending shifting dinner earlier when late meals repeatedly coincide with hyperglycemic excursions or sleep disruption, while also automating monitoring for clinicians via dashboards and telehealth integration. Such platforms have shown promise in improving adherence to diet and lifestyle prescriptions, enabling remote titration of meal-timing interventions, and supporting long-term behaviour change in obesity and type 2 diabetes management, making chrononutrition a practical pillar of precision metabolic care rather than a purely theoretical construct [49,50,54,55,56,57].

Future Directions and Research Gaps

Future work in chrononutrition is constrained by short intervention durations, small sample sizes, and highly controlled settings, which limit conclusions about long-term cardiometabolic and mortality outcomes, while substantial inter-individual variability and a lack of standardized, scalable circadian biomarkers (beyond melatonin and actigraphy) further impede translation. More personalized approaches are needed that integrate objective circadian phenotyping and chronotypes into adaptive nutrient-timing algorithms, replacing uniform eating windows with tailored plans that optimize the placement of caloric peaks and fasting periods relative to each person’s biological day [58,59].

AI and digital health can advance the field by extracting circadian features from continuous glucose, sleep, activity, and heart-rate data, enabling detection of misalignment and simulation of timing-based interventions for metabolic optimization at both individual and population levels. Integrating chrononutrition with microbiome chronobiology and metabolomics in longitudinal, multi-omic studies may reveal rhythmic signatures of healthy versus unhealthy eating patterns and identify biomarkers that predict response to specific timing interventions, pushing chrononutrition toward a true precision medicine paradigm [58,59].

Conclusion

Chrononutrition represents a promising new frontier in preventive strategies for metabolic and aging wellness, reframing nutrition through the lens of circadian biology and demonstrating that the temporal distribution of energy intake can modulate glycemic control, lipid handling, blood pressure, and cellular stress responses in ways that are independent of, yet complementary to, traditional dietary modification. Positioning timing as a “fourth dimension” of nutrition alongside quantity, quality, and macronutrient balance, acknowledges that aligning feeding-fasting cycles with endogenous circadian rhythms is integral to maintaining metabolic homeostasis, preserving circadian amplitude with aging, and engaging longevity-related pathways such as sirtuin signaling, mTOR inhibition, autophagy, and NAD+/AMPK-mediated metabolic adaptation.

Looking ahead, clinically guided, circadian-aligned lifestyle practices should be incorporated into standard metabolic care, using structured but flexible time-restricted eating windows, earlier caloric loading, and protection of the nocturnal fasting interval, individualized by chronotype, comorbidities, and cultural context. Digital health tools, integrating continuous glucose monitoring, wearable-derived sleep and activity data, and AI-driven analytics can operationalize this paradigm by continuously assessing circadian alignment, personalizing meal-timing prescriptions, and supporting long-term adherence, thereby translating chrononutrition from an emerging research concept into a core pillar of precision prevention and healthy longevity.

Reference

  1. Radziuk JM. The Suprachiasmatic Nucleus, Circadian Clocks, and the Liver. Diabetes [Internet]. 2013 Mar 21;62(4):1017–9. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3609582/
  2. Bautista J, Sofía Ojeda-Mosquera, Ordóñez-Lozada D, Andrés López-Cortés. Peripheral clocks and systemic zeitgeber interactions: from molecular mechanisms to circadian precision medicine. Frontiers in Endocrinology [Internet]. 2025 May 29;16. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC12158691/
  3. BaHammam AS, Pirzada R. Timing matters: The interplay between early mealtime, circadian rhythms, gene expression, circadian hormones, and metabolism—a narrative review. Clocks & sleep [Internet]. 2023 Sep 6;5(3):507–35. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC10528427/
  4. Begemann K, Rawashdeh O, Olejniczak I, Violetta Pilorz, Vinícius L, Osorio-Mendoza J, et al. Endocrine regulation of circadian rhythms. Deleted Journal [Internet]. 2025 Mar 8;2(1). Available from: https://www.nature.com/articles/s44323-025-00024-6
  5. Peters B, Vahlhaus J, Pivovarova-Ramich O. Meal timing and its role in obesity and associated diseases. Frontiers in Endocrinology. 2024 Mar 22;15.
  6. Dong Y, Lam SM, Li Y, Li MD, Shui G. The circadian clock at the intersection of metabolism and aging – emerging roles of metabolites. Journal of Genetics and Genomics [Internet]. 2025 Apr 29; Available from: https://www.sciencedirect.com/science/article/pii/S1673852725001237?ref=pdf_download&fr=RR-2&rr=980009e49f153929
  7. Wang J, Cao M, Li S, Pei W, Li J, Wang Z. Circadian clock genes: Their influence on liver metabolism, disease development and treatment (Review). Molecular Medicine Reports. 2025 Oct 14;33(1):1–18.
  8. Woodie LN, Alberto AJ, Krusen BM, Melink LC, Lazar MA. Genetic synchronization of the brain and liver molecular clocks defend against chrono-metabolic disease. Proceedings of the National Academy of Sciences. 2024 Dec 12;121(51).
  9. Mar Calvo-Malvar, Óscar Lado-Baleato, Ríos AC, Fernández CP, Benítez-Calvo A, Fernandez-Merino C, et al. Age, Sex, BMI, Meal Timing, and Glycemic Response to Meal Glycemic Load. JAMA Network Open [Internet]. 2025 Sep 23;8(9):e2533193–3. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC12457981/
  10. Aoyama S, Shibata S. Time-of-Day-Dependent Physiological Responses to Meal and Exercise. Frontiers in Nutrition [Internet]. 2020 Feb 28;7. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7059348/
  11. Vahlhaus J, Peters B, Hornemann S, Ost AC, Kruse M, Busjahn A, et al. Later eating timing in relation to an individual internal clock is associated with lower insulin sensitivity and affected by genetic factors. EBioMedicine [Internet]. 2025 Jun;116:105737. Available from: https://pubmed.ncbi.nlm.nih.gov/40305967/
  12. Díaz-Rizzolo DA, Baez S, Popp CJ, Rabiah Borhan, Sordi-Guth A, Emily, et al. Late eating is associated with poor glucose tolerance, independent of body weight, fat mass, energy intake and diet composition in prediabetes or early onset type 2 diabetes. Nutrition and Diabetes [Internet]. 2024 Oct 25;14(1). Available from: https://www.nature.com/articles/s41387-024-00347-6#citeas
  13. M A, Sirimon Reutrakul, Petersen G, Knutson KL. Associations between Timing and Duration of Eating and Glucose Metabolism: A Nationally Representative Study in the U.S. Associations between Timing and Duration of Eating and Glucose Metabolism: A Nationally Representative Study in the US [Internet]. 2023 Feb 1;15(3):729–9. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9919634/
  14. Morris CJ, Yang JN, Garcia JI, Myers S, Bozzi I, Wang W, et al. Endogenous circadian system and circadian misalignment impact glucose tolerance via separate mechanisms in humans. Proceedings of the National Academy of Sciences of the United States of America [Internet]. 2015 Apr 28;112(17):E2225–34. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4418873/
  15. Reytor-González C, Simancas-Racines D, Náthaly Mercedes Román-Galeano, Annunziata G, Galasso M, Raynier Zambrano-Villacres, et al. Chrononutrition and Energy Balance: How Meal Timing and Circadian Rhythms Shape Weight Regulation and Metabolic Health. Nutrients [Internet]. 2025 Jun 27;17(13):2135–5. Available from: https://www.mdpi.com/2072-6643/17/13/2135?utm_source=chatgpt.com
  16. Hussain MM, Pan X. Circadian Regulation of Macronutrient Absorption. Journal of Biological Rhythms. 2015 Aug 12;30(6):459–69.
  17. Aoyama S, Shibata S. Time-of-Day-Dependent Physiological Responses to Meal and Exercise. Frontiers in Nutrition [Internet]. 2020 Feb 28;7. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7059348/
  18. Rynders CA, Morton SJ, Bessesen DH, Wright KP, Broussard JL. Circadian Rhythm of Substrate Oxidation and Hormonal Regulators of Energy Balance. Obesity. 2020 May 28;28(S1).
  19. Kelly KP, McGuinness OP, Buchowski M, Hughey JJ, Chen H, Powers J, et al. Eating breakfast and avoiding late-evening snacking sustains lipid oxidation. PLoS Biology [Internet]. 2020 Feb 27 [cited 2020 Oct 12];18(2). Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7046182/
  20. Reytor-González C, Simancas-Racines D, Náthaly Mercedes Román-Galeano, Annunziata G, Galasso M, Raynier Zambrano-Villacres, et al. Chrononutrition and Energy Balance: How Meal Timing and Circadian Rhythms Shape Weight Regulation and Metabolic Health. Nutrients [Internet]. 2025 Jun 27;17(13):2135–5. Available from: https://www.mdpi.com/2072-6643/17/13/2135?utm_source=chatgpt.com
  21. Gong Y, Zhang H, Feng J, Ying L, Ji M, Wei S, et al. Time-restricted feeding improves metabolic syndrome by activating thermogenesis in brown adipose tissue and reducing inflammatory markers. Frontiers in Immunology. 2025 Jan 24;16.
  22. Ruddick-Collins LC, Johnston JD, Morgan PJ, Johnstone AM. The Big Breakfast Study: Chrono-nutrition influence on energy expenditure and bodyweight. Nutrition Bulletin [Internet]. 2018 May 8;43(2):174–83. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969247/pdf/NBU-43-174.pdf
  23. Cantó C, Jiang LQ, Deshmukh AS, Mataki C, Coste A, Lagouge M, et al. Interdependence of AMPK and SIRT1 for Metabolic Adaptation to Fasting and Exercise in Skeletal Muscle. Cell Metabolism [Internet]. 2010 Mar [cited 2019 Nov 19];11(3):213–9. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3616265/
  24. Li Y, Liang J, Tian X, Chen Q, Zhu L, Wang H, et al. Intermittent fasting promotes adipocyte mitochondrial fusion through Sirt3-mediated deacetylation of Mdh2. British Journal of Nutrition [Internet]. 2023 Nov 1;130(9):1473–86. Available from: https://www.cambridge.org/core/journals/british-journal-of-nutrition/article/intermittent-fasting-promotes-adipocyte-mitochondrial-fusion-through-sirt3mediated-deacetylation-of-mdh2/B19A226CD1CA3DB3414825585EF3BE52
  25. Gong Y, Zhang H, Feng J, Ying L, Ji M, Wei S, et al. Time-restricted feeding improves metabolic syndrome by activating thermogenesis in brown adipose tissue and reducing inflammatory markers. Frontiers in Immunology. 2025 Jan 24;16.
  26. Zhu Y, Yan Y, Gius DR, Vassilopoulos A. Metabolic regulation of Sirtuins upon fasting and the implication for cancer. Current Opinion in Oncology. 2013 Nov;25(6):630–6.
  27. Ho L, Allen Sam Titus, Kushal Kr. Banerjee, George S, Lin W, Shaunak Deota, et al. SIRT4 regulates ATP homeostasis and mediates a retrograde signaling via AMPK. 2013 Nov 26;5(11):835–49.
  28. Sutton EF, Beyl R, Early KS, Cefalu WT, Ravussin E, Peterson CM. Early Time-Restricted Feeding Improves Insulin Sensitivity, Blood Pressure, and Oxidative Stress Even without Weight Loss in Men with Prediabetes. Cell Metabolism [Internet]. 2018 Jun;27(6):1212-1221.e3. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5990470/
  29. Charlot A, Hutt F, Sabatier E, Zoll J. Beneficial Effects of Early Time-Restricted Feeding on Metabolic Diseases: Importance of Aligning Food Habits with the Circadian Clock. Nutrients [Internet]. 2021 Apr 22;13(5):1405. Available from: https://dx.doi.org/10.3390%2Fnu13051405
  30. Duan D, Bhat S, Jun JC, Sidhaye A. Time-Restricted Eating in Metabolic Syndrome–Focus on Blood Pressure Outcomes. Current Hypertension Reports. 2022 Sep 6;24(11):485–97.
  31. Heath RJ, Welbourne J, Martin D. What are the effects of time‐restricted eating upon metabolic health outcomes in individuals with metabolic syndrome: A scoping review. Physiological Reports. 2025 May 1;13(9).
  32. Xie Z, Sun Y, Ye Y, Hu D, Zhang H, He Z, et al. Randomized controlled trial for time-restricted eating in healthy volunteers without obesity. Nature Communications. 2022 Feb 22;13(1).
  33. Charlot A, Hutt F, Sabatier E, Zoll J. Beneficial Effects of Early Time-Restricted Feeding on Metabolic Diseases: Importance of Aligning Food Habits with the Circadian Clock. Nutrients [Internet]. 2021 Apr 22;13(5):1405. Available from: https://dx.doi.org/10.3390%2Fnu13051405
  34. Duan D, Bhat S, Jun JC, Sidhaye A. Time-Restricted Eating in Metabolic Syndrome–Focus on Blood Pressure Outcomes. Current Hypertension Reports. 2022 Sep 6;24(11):485–97.
  35. Scheer FAJL, Hilton MF, Mantzoros CS, Shea SA. Adverse metabolic and cardiovascular consequences of circadian misalignment. Proceedings of the National Academy of Sciences. 2009 Mar 2;106(11):4453–8.
  36. Morris CJ, Purvis TE, Mistretta J, Scheer FAJL. Effects of the Internal Circadian System and Circadian Misalignment on Glucose Tolerance in Chronic Shift Workers. The Journal of Clinical Endocrinology and Metabolism [Internet]. 2016 Mar 1;101(3):1066–74. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4803172/
  37. Leproult R, Holmbäck U, Van Cauter E. Circadian Misalignment Augments Markers of Insulin Resistance and Inflammation, Independently of Sleep Loss. Diabetes. 2014 Jan 23;63(6):1860–9.
  38. Charlot A, Hutt F, Sabatier E, Zoll J. Beneficial Effects of Early Time-Restricted Feeding on Metabolic Diseases: Importance of Aligning Food Habits with the Circadian Clock. Nutrients [Internet]. 2021 Apr 22;13(5):1405. Available from: https://dx.doi.org/10.3390%2Fnu13051405
  39. Lages M, Carmo-Silva S, Barros R, Guarino MP. Effects of Time-Restricted Eating on Body Composition, Biomarkers of Metabolism, Inflammation, Circadian System and Oxidative Stress in Overweight and Obesity: An Exploratory Review. Proceedings of The Nutrition Society. 2024 Nov 20;1–31.
  40. Su Y, Wang M, Chen J, Bao Y, Wen R, Ren HW, et al. Progress in understanding how clock genes regulate aging and associated metabolic processes. Frontiers in Physiology [Internet]. 2025 Sep 23;16. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC12500579/
  41. Cobarro CG, Soares LI, Yevheniy Kutsenko, Tomas-Loba A. Circadian system and aging: where both times interact. Frontiers in Aging. 2025 Oct 17;6.
  42. Rahman SA, Gathungu RM, Marur VR, St. Hilaire MA, Scheuermaier K, Belenky M, et al. Age-related changes in circadian regulation of the human plasma lipidome. Communications Biology [Internet]. 2023 Jul 20;6(1). Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC10359364/
  43. Yin Z, Klionsky DJ. Intermittent time-restricted feeding promotes longevity through circadian autophagy. Autophagy. 2022 Feb 27;1–2.
  44. Longo VD, Di Tano M, Mattson MP, Guidi N. Intermittent and periodic fasting, longevity and disease. Nature Aging [Internet]. 2021 Jan;1(1):47–59. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8932957/
  45. Zhang M, Shi L, Meng X, Dong Y, Sun Y, Qian Q, et al. Mechanism study of exercise intervention on circadian disruption in Alzheimer’s disease. Frontiers in Neuroscience [Internet]. 2025 Dec 11 [cited 2026 Jan 14];19:1696673–3. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC12738941/
  46. Zhai J, Kongsberg WH, Pan Y, Hao C, Wang X, Sun J. Caloric restriction induced epigenetic effects on aging. Frontiers in Cell and Developmental Biology. 2023 Jan 13;10.
  47. com. Longevity Prescription: Diet, Fasting, and Proven Anti-Aging Strategies [Internet]. Nad.com. 2025 [cited 2026 Jan 14]. Available from: https://www.nad.com/news/longevity-prescription
  48. Cantó C, Jiang LQ, Deshmukh AS, Mataki C, Coste A, Lagouge M, et al. Interdependence of AMPK and SIRT1 for Metabolic Adaptation to Fasting and Exercise in Skeletal Muscle. Cell Metabolism [Internet]. 2010 Mar;11(3):213–9. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3616265/
  49. Mentzelou M, Papadopoulou SK, Psara E, Voulgaridou G, Pavlidou E, Androutsos O, et al. Chrononutrition in the Prevention and Management of Metabolic Disorders: A Literature Review. Nutrients [Internet]. 2024 Jan 1 [cited 2024 Mar 7];16(5):722. Available from: https://www.mdpi.com/2072-6643/16/5/722
  50. Agrawal K, Goktas P, Kumar N, Leung MF. Artificial intelligence in personalized nutrition and food manufacturing: a comprehensive review of methods, applications, and future directions. Frontiers in Nutrition. 2025 Jul 23;12.
  51. Longo-Silva G, Serenini R, Pedrosa A, Lima M, Soares L, Melo J, et al. Chrononutrition patterns and their association with body weight: Differences across multiple chronotypes. Endocrinología, Diabetes y Nutrición [Internet]. 2024 Sep 21;72(1):4–13. Available from: https://www.sciencedirect.com/science/article/abs/pii/S2530016424001502
  52. Rovira-Llopis S, Luna-Marco C, Perea-Galera L, Bañuls C, Morillas C, Victor VM. Circadian alignment of food intake and glycaemic control by time-restricted eating: A systematic review and meta-analysis. Reviews in Endocrine & Metabolic Disorders [Internet]. 2023 Nov 22; Available from: https://pubmed.ncbi.nlm.nih.gov/37993559/
  53. M A, Sirimon Reutrakul, Petersen G, Knutson KL. Associations between Timing and Duration of Eating and Glucose Metabolism: A Nationally Representative Study in the U.S. Associations between Timing and Duration of Eating and Glucose Metabolism: A Nationally Representative Study in the US [Internet]. 2023 Feb 1;15(3):729–9. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9919634/
  54. Domingues MF, Dimitropoulos K, Hart K, Dias SB. Editorial: Smart devices for personalized nutrition and healthier lifestyle behavior change. Frontiers in Nutrition. 2025 Apr 29;12.
  55. Gavai AK, Jos van Hillegersberg. AI-driven personalized nutrition: RAG-based digital health solution for obesity and type 2 diabetes. PLOS Digital Health. 2025 May 6;4(5):e0000758–8.
  56. Chen YE, Ku CW, Chong MF, Yap F, Chan JKY, Loy SL, et al. Associations of >1-h compared with 1-h meal timing variability (eating jetlag) with plasma glycemic parameters and continuous glucose monitoring measures among pregnant females: a prospective cohort study. The American Journal of Clinical Nutrition [Internet]. 2025 Apr 26;122(1):244–54. Available from: https://www.sciencedirect.com/science/article/abs/pii/S0002916525002436
  57. Alessio Abeltino, Alessia Riente, Bianchetti G, Serantoni C, Marco De Spirito, Stefano Capezzone, et al. Digital applications for diet monitoring, planning, and precision nutrition for citizens and professionals: a state of the art. Nutrition reviews. 2024 May 9;83(2).
  58. Fuad SA, Ginting RP, Lee MW. Chrononutrition: Potential, Challenges, and Application in Managing Obesity. International Journal of Molecular Sciences [Internet]. 2025 May 26;26(11):5116. Available from: https://www.mdpi.com/1422-0067/26/11/5116
  59. Franzago M, Alessandrelli E, Notarangelo S, Stuppia L, Vitacolonna E. Chrono-Nutrition: Circadian Rhythm and Personalized Nutrition. International Journal of Molecular Sciences. 2023 Jan 1;24(3):2571.

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