Time-restricted Eating Research Articles

Effects of Time-Restricted Eating on Body Composition, Biomarkers of Metabolism, Inflammation, Circadian System and Oxidative Stress in Overweight and Obesity: An Exploratory Review.

Obesity is a chronic, complex and multi-factorial condition with an increasing prevalence worldwide. Irregular eating schedules might be a contributing factor to these numbers through the dysregulation of the circadian system. Time-restricted eating (TRE), an approach that limits eating windows, has been studied as a strategy to treat obesity, aligning eating occasions with metabolic circadian rhythms. This review aims to provide an overview of the impact of TRE protocols on metabolic, inflammatory, oxidative stress, and circadian rhythm biomarkers in people with overweight or obesity. Most studies report significant weight loss following TRE protocols. While glucose levels decreased in nearly all TRE interventions, only a few studies demonstrated statistically significant differences when compared to the control groups. The findings for CRP and TNF-α were inconsistent, with limited significant differences. Changes in lipid profile changes were variable and generally did not reach statistical significance. Both 4-hour and 6-hour TRE interventions significantly reduced 8-isoprostane levels. Additionally, TRE significantly altered clock gene expression, as well as that of genes associated with metabolic regulation in subcutaneous adipose tissue. While the evidence is still inconsistent, limiting eating to a consistent daily window of 8 to 12 hours can improve insulin sensitivity, reduce blood glucose, cholesterol and triglyceride levels and promote weight loss. These effects are likely attributable to both direct metabolic impacts and indirect benefits from weight loss and improved dietary habits. However, data on circadian, inflammatory, and specific metabolic biomarkers remain scarce and occasionally contradictory, highlighting the need for further research on these interventions.

Effect of Intermittent Fasting on Immune Parameters and Intestinal Inflammation.

Intermittent fasting (IF), including alternate day fasting (ADF) and time-restricted feeding (TRF) or, in humans, time-restricted eating (TRE), has been associated with the prevention and improvement of diseases, including inflammatory bowel disease (IBD). This review summarizes 20 animal and human studies on the influence of IF on intestinal inflammation. In the animal studies, TRF and ADF improved histological scores, inflammatory markers, markers of oxidative stress, and microbiota composition. Apart from the studies on Ramadan fasting, there are no studies on IF in IBD patients, so human studies on IF in healthy people were included. The studies on Ramadan fasting showed almost no effects, but this particular type of fasting is not directly comparable to TRE or ADF. However, TRE and ADF appear to have anti-inflammatory effects in healthy individuals, as they significantly reduce CRP levels and inflammatory markers. TRE also improved the composition of microbiota and the circadian oscillation of clock genes. The beneficial effects of TRE and ADF in healthy people appear to depend on the number of uninterrupted days of fasting, while in animal studies improvements in colitis have been observed regardless of the duration of fasting.

Effects of different types of intermittent fasting on metabolic outcomes: an umbrella review and network meta-analysis

BackgroundIntermittent fasting (IF) holds promise for enhancing metabolic health. However, the optimum IF forms and their superiority over continuous energy restriction (CER) remain unclear due to disconnected findings.MethodsWe systematically searched PubMed, Embase, and the Cochrane databases for meta-analyses of randomized controlled trials (RCTs) investigating the association between IF and metabolic health outcomes. Subsequently, we performed an umbrella review and network meta-analysis (NMA) to evaluate the efficacy of different forms of IF (time-restricted eating (TRE), alternate-day fasting (ADF), and 5:2 diet (regular eating for 5 days and energy restriction for 2 days per week)) compared to CER and usual diets on metabolic health outcomes. To assess the certainty of both direct and indirect estimates, we employed the Confidence in Network Meta-Analysis (CINeMA) approach. Additionally, we calculated the surface under the cumulative ranking curve (SUCRA) for each dietary strategy to determine their ranking in terms of metabolic health benefits.ResultsTen of the best and non-redundant meta-analysis studies, involving 153 original studies and 9846 participants, were included. When considering direct evidence only, all IF forms significantly reduced body weight compared to usual diets. In NMA incorporating indirect evidence, all IF regimens also significantly reduced body weight compared to usual diets. In the SUCRA of NMA, IF ranked higher than usual diets or CER in 85.4% and 56.1% of the outcomes, respectively. ADF had the highest overall ranking for improving metabolic health (ranked first: 64.3%, ranked second: 14.3%).ConclusionsOverall, all IF forms demonstrate potentials to improve metabolic health, with ADF appearing to produce better outcomes across investigated outcomes. Further high-quality trials are warranted to confirm the (relative) efficacy of IF on metabolic health.Trial registrationPROSPERO (record no: CRD42022302690).

Meal Timing and Anthropometric and Metabolic Outcomes

Meal timing strategies, such as time-restricted eating (TRE), reducing meal frequency, or altering calorie distribution across the day, have gained interest for their potential to enhance weight loss and metabolic health, particularly in managing chronic diseases, yet their long-term benefits are not known. To evaluate the association between meal timing strategies (≥12 weeks) and anthropometric and metabolic indicators. Medline, Embase, CINAHL, and Cochrane CENTRAL were searched from inception to October 17, 2023. Randomized clinical trials, regardless of language and publication date, involving adults 18 years and older, evaluating within-day meal timing patterns for 12 or more weeks, and reporting anthropometric measures were included. Studies were excluded if participants had eating disorders, prior significant weight change, underwent bariatric surgery, were pregnant, or if controlled variables differed between groups. Study quality was determined via Risk of Bias 2.0 tool. Data were extracted independently by multiple reviewers. Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines were used. Meta-analysis was performed using random-effects model on pooled continuous outcomes with 2 or more studies. Weight change in kilograms, reported as between-group mean difference with 95% CIs. Sixty-nine reports of 29 randomized clinical trials including 2485 individuals (1703 [69%] female; mean [SD] age, 44 [9.5] years; and mean [SD] body mass index, 33 [3.5]) were included. Study interventions included TRE (17 studies), meal frequency (8 studies), and calorie distribution (4 studies). There were some concerns of risk of bias for 7 studies and high concerns for 22 studies. Statistically significant weight change was observed in TRE when compared with control (-1.37 kg; 95% CI, -1.99 to -0.75 kg). Lower meal frequency and earlier caloric distribution were also both associated with greater change (-1.85 kg; 95% CI, -3.55 to -0.13 kg; and -1.75 kg; 95% CI, -2.37 to -1.13 kg, respectively). The findings of this meta-analysis suggest that TRE, lower meal frequency, and earlier caloric distribution in the day may reduce weight compared with standard care and/or nutritional advice; however, the effect sizes found were small and of uncertain clinical importance. High heterogeneity and risk of bias among included studies led to concerns about the certainty of the underpinning evidence. Further research, including trials with larger sample sizes, standardized interventions with prescribed or matched energy intake, and longer follow-up, are needed.

Time-restricted eating reveals a “younger” immune system and reshapes the intestinal microbiome in human

Time-restricted eating (TRE) has been shown to extent lifespans in drosophila and mouse models by affecting metabolic and anti-inflammatory activities. However, the effect of TRE on the human immune system, especially on immunosenescence, intestinal microbiome, and metabolism remains unclear. We conducted a 30-day 16:8 TRE single-arm clinical trial with 49 participants. Participants consumed daily meals from 9 am to 5 pm, provided by a nutrition canteen with a balanced, calorie-appropriate nutrition, which is designed by clinical nutritionists (ChiCTR2200058137). We monitored weight changes and weight-related parameters and focused on changes in the frequency of CD4+ senescent T cells, immune repertoire from peripheral blood, as well as serum metabolites and gut microbiota. We found that up to 95.9% of subjects experienced sustained weight loss after TRE. The frequency of circulating senescent CD4+ T cells was decreased, while the frequency of Th1, Treg, Tfh-like, and B cells was increased. Regarding the immune repertoire, the proportions of T cell receptor alpha and beta chains were increased, whereas B cell receptor kappa and lambda chains were reduced. In addition, a reduced class switch recombination from IgM to IgA was observed. TRE upregulated the levels of anti-inflammatory and anti-aging serum metabolites named sphingosine-1-phosphate and prostaglandin-1. Additionally, several anti-inflammatory bacteria and probiotics were increased, such as Akkermansia and Rikenellaceae, and the composition of the gut microbiota tended to be “younger”. Overall, TRE showed multiple anti-aging effects, which may help provide humans maintain a healthy lifestyle to stay “young”. Clinical Trial Registration URL: https://www.chictr.org.cn/showproj.html?proj=159876.

The Effect of Time-Restricted Eating on Cardiometabolic Risk Factors: A Systematic Review and Meta-Analysis.

Background/Objectives: Endogenous metabolic pathways periodically adjust with fluctuations in day and night, a biological process known as circadian rhythm. Time-restricted eating (TRE) aligns the time of food intake with the circadian rhythm. This study aims to investigate the effects of TRE on body weight, body composition and cardiometabolic risk factors. Methods: We reviewed articles from PubMed and Cochrane libraries for clinical trials that compare TRE with regular diet without calorie restriction. We conducted a meta-analysis of 26 studies. Results: Participants who followed TRE demonstrated reduction in body weight [mean-MD: -1.622 kg, (95% confidence interval (CI -2.302 to -0.941)], body mass index (BMI) [MD: -0.919 kg/m2 (95% CI: -1.189 to -0.650)], waist circumference [MD: -2.015 cm (95% CI: -3.212 to -0.819] and whole-body fat mass (WBFM) [MD: -0.662 kg (95% CI: -0.795 to -0.530)]. Improvements in cardiometabolic risk factors such as a decrease in insulin concentrations [MD: -0.458 mIU/L, (95% CI: -0.843 to -0.073)], total cholesterol [MD: -2.889 mg/dL (95% CI: -5.447 to -0.330) and LDL concentrations [MD: -2.717 mg/dL (95% CI: -4.412 to -1.021)] were observed. Conclusions: TRE is beneficial for weight loss and improvements in cardiometabolic risk factors. Further large-scale clinical trials are needed to confirm these findings.

A pre-post trial to examine biological mechanisms of the effects of time-restricted eating on symptoms and quality of life in bipolar disorder

BackgroundThe primary objective of this trial is to examine the mechanisms of time-restricted eating (TRE) as an adjunct to psychiatric care for people with bipolar disorder (BD) with sleep or circadian disruptions. This study builds on prior studies of circadian disruption in BD as well as growing evidence that TRE improves circadian functioning.MethodsOne-hundred fifty participants diagnosed with BD 1 or II will be recruited via advertising in the local community. Main inclusion criteria include: obtaining medical treatment for BD; current sleep or circadian problems; self-reported eating period of ≥ 12 h; no eating disorder or other health conditions that would hinder or limit the safety of following TRE; and not currently experiencing a mood episode, acute suicidality, psychosis, alcohol or substance use disorder. Participants will be asked to complete a baseline period in which daily food intake is logged online for two weeks. After baseline, participants will be asked to follow TRE for 8 weeks and to continue to complete daily food logging during this time. Symptom severity interviews will be conducted by phone or videoconference at baseline, mid-intervention (6 weeks post-baseline), end of intervention (10 weeks post-baseline), and 6 months post-baseline. Self-rated symptom severity and quality of life data will be gathered online at the same time points as symptom severity interviews, and at 16 weeks post-baseline (6 weeks after the TRE period ends). To assess potential mechanisms of change, we will examine the change in diurnal amplitude of ‘clock’ gene expression as a primary mediator at 8 weeks compared to baseline. We will further test whether diurnal amplitude of clock gene expression is predictive above and beyond the role of two covariate potential mediators, glucose tolerance and inflammation at 8 weeks relative to baseline. To provide an index of whether TRE successfully decreases emotional lability, participants will be asked to complete 5 mood assessments per day for 7 days at baseline and at 10 weeks. These mood assessments will be optional.DiscussionThe planned research will provide novel and important information on whether TRE improves sleep/circadian rhythm problems, along with reductions in mood symptoms and improvements in quality of life, for individuals with BD.Trial registrationClinicalTrials.gov ID: NCT06555406.

Effect of exercise alone and in combination with time-restricted eating on cardiometabolic health in menopausal women

There is a need to investigate the effect of lifestyle modifications on cardiometabolic health-related issues that occur during menopause. The aim of this study was to compare the effect of resistance and endurance circuit training program alone (exercise group, n = 34) with the effect of time-restricted eating (16:8) combined with a training program (combination group, n = 28) on cardiometabolic health in 62 menopausal women (aged 51.3 ± 4.69 years). Testing was conducted before and after a 12-week period and included an assessment of body composition, glycemic control, lipid panel, blood pressure, and anthropometric measurements. Decreases in body mass index and systolic blood pressure were significantly greater in the combination group than in the exercise group (F(1,60) = 4.482, p = 0.038, η2 = 0.07; F(1,57) = 5.215, p = 0.026, η2 = 0.08, respectively, indicating moderate effects). There were significant decreases in fat mass (p = 0.001, r = 0.654), glucose level (p = 0.017, r = 0.459), insulin level (p = 0.013, r = 0.467), homeostatic model assessment for insulin resistance (p = 0.009, r = 0.499), waist circumference (p = 0.002, r = 0.596), and waist-to-height ratio (p = 0.003, r = 0.588) (indicating moderate effect) in the combination group, while there were no significant changes in the exercise group. There were no changes in lipid panel indicators in either group. This is the first study to investigate the effect of time-restricted eating combined with exercise in menopausal women. The results of the study provide evidence that the combination of time-restricted eating and exercise leads to a greater body mass index reduction than exercise alone in menopausal women.Trial registration: ClinicalTrials.gov, NCT06138015 registered 18 November 2023—Retrospectively registered, https://clinicaltrials.gov/study/NCT06138015.

Time-Restricted Eating Versus Daily Calorie Restriction: Effect on Sleep in Adults with Obesity over 12 Months.

Objective: The aim of this secondary analysis was to compare the effects of time-restricted eating (TRE) versus daily calorie restriction (CR) on sleep quality, duration, insomnia severity, and risk of obstructive sleep apnea in adults with obesity over one year. Methods: A total of 90 participants were randomized to one of three groups for 12 months: 8 h TRE (eating only between 12 p.m. and 8 p.m.); CR (25% daily calorie restriction) or a no-intervention control group. Results: By the end of the study, weight loss was 4.61 kg (95% CI; 7.37 to 1.85 kg; p ≤ 0.01) for the TRE group and 5.42 kg (CI; 9.13 to 1.71 kg; p ≤ 0.01) for the CR group, with no statistically significant difference between TRE and CR (0.81 kg [CI; 3.07 to 4.69]; p = 0.68]). Self-reported sleep quality, sleep duration, insomnia severity, and risk of obstructive sleep apnea did not change in the TRE or CR groups versus controls by month 12. Conclusions: These findings suggest that the weight loss produced by TRE and CR does not have any impact on various sleep parameters in adults with obesity over one year.

Comparing the effects of time-restricted eating on glycaemic control in people with type 2 diabetes with standard dietetic practice: A randomised controlled trial

AimsTo test the efficacy of time-restricted eating (TRE) in comparison to dietitian-led individualised dietary guidance to improve HbA1c in people with Type 2 diabetes mellitus. MethodsIn a parallel groups design, 51 adults (35–65 y) with Type 2 diabetes mellitus and overweight/obesity (HbA1c ≥6.5% (48 mmol/mol), BMI ≥25-≤40 kg/m2) commenced a six-month intervention. Following baseline, participants were randomised to TRE (1000–1900 h) or DIET (individualised dietetic guidance) with four consultations over four months. Changes in HbA1c (primary), body composition, and self-reported adherence (secondary) were analysed using linear mixed models. A non-inferiority margin of 0.3% (4 mmol/mol) HbA1c was set a priori. ResultsForty-three participants (56 ± 8 y, BMI: 33 ± 5 kg/m2, HbA1c: 7.6 ± 0.8%) completed the intervention. HbA1c was reduced (P=0.002; TRE: −0.4% (−5 mmol/mol), DIET: −0.3% (−4 mmol/mol)) with no group or interaction effects; TRE was non-inferior to DIET (−0.11%, 95%CI: −0.50% to 0.28%). Body mass reduced in both groups (TRE: −1.7 kg; DIET: −1.2 kg) via ∼900 kJ/d spontaneous energy reduction (P<0.001). Self-reported adherence was higher in TRE versus DIET (P<0.001). ConclusionsWhen individualised dietary guidance is not available, effective, and/or suitable, TRE may be an alternative dietary strategy to improve glycaemic control in people with Type 2 diabetes mellitus.

Effects of fortified eggs and time-restricted eating on cardiometabolic health: The prosperity trial

BackgroundGiven the increasing interest in dietary interventions to improve cardiovascular health, this trial assessed the impact of fortified eggs (FE) versus non-egg supplemented diet and time-restricted eating (TRE) versus usual care diet on cardiovascular biomarkers. MethodsThe study was a unblinded, 2-by-2 factorial design, which randomized patients, with either a prior cardiovascular event or two cardiovascular risk factors, to FE or a non-egg supplemented diet and TRE or usual care diet. Patients randomized to FE were instructed to consume at least 12 FE/week (with eggs provided); those on a non-egg supplemented diet restricted egg consumption to <2 eggs/week. TRE participants were instructed to consume all calories within an 8-hour window daily and fasted for the remaining 16 hours. Patients randomized to usual diet were advised to maintain current dietary habits. Follow-up was performed in-person at 1 and 4 months, and telephone calls at 2 and 3 months. Co-primary endpoints were 4-month LDL- and HDL-cholesterol. Secondary endpoints included additional lipids, cardiometabolic- and inflammatory biomarkers and micronutrient levels at 4-months. ResultsOverall, 140 patients were randomized with median (25th, 75th percentiles) age 66 (58, 73) years; 72 (51%) women, 38 (27%) Black, and 33 (24%) with diabetes mellitus. The difference in least squares (LS) means from baseline to 4-months for HDL and LDL levels revealed no significant clinical difference between FE vs. non-egg supplemented diet (HDL: -0.64 mg/dL [95% CI: -3.86, 2.58]; LDL: -3.14 mg/dL [-10.81, 4.52]) and TRE vs. usual care diet (HDL: 1.51 mg/dL [-1.65, 4.68]; LDL 1.17 mg/dL [-6.36, 8.70]). Pre-specified subgroups revealed a non-significant HDL increase and LDL decrease with FE in patients ≥65 years. ConclusionsThese data did not demonstrate clinically relevant differences in changes in LDL and HDL levels over 4 months with FE and TRE compared with non-egg supplemented diet and usual care diet, respectively, providing evidence that adverse short-term lipid and biomarker changes did not occur with FE consumption. Trial RegistrationClinicalTrials.gov Identifier: NCT04673721.

Effect of Time-Restricted Eating on Circulating Levels of IGF1 and Its Binding Proteins in Obesity: An Exploratory Analysis of a Randomized Controlled Trial.

This study aimed to investigate the effects of TRE on plasma IGF1, IGFBP1, IGFBP2, and IGFBP3, and whether these effects were mediated by weight loss or body composition changes. Insulin sensitivity, glucose control, adipokines, and inflammatory markers were also examined. An exploratory analysis of an 8-week randomized controlled trial implementing a daily TRE intervention was carried out. This study was conducted at the University of Illinois at Chicago in 2019. Participants with obesity were randomized to 4 or 6 h TRE (n = 35) or a control (n = 14) group. Plasma biomarkers were measured by ELISA at baseline and week 8. In a sub-analysis, participants were stratified into higher- (>3.5%) and lower- (≤3.5%) weight-loss groups. Participants fasted daily from 7 p.m. to 3 p.m. in the 4 h TRE group (20 h) and from 7 p.m. to 1 p.m. in the 6 h TRE group (18 h), followed by ad libitum eating for the remainder of the day. Controls received no dietary recommendations. IGF1, IGFBPs, hsCRP, and adipokines were the main outcome measures of this analysis. Repeated measures ANOVA and mediation analysis were conducted. Body weight significantly decreased with TRE (-3.6 ± 0.3%), contrasting with controls (+0.2 ± 0.5%, p < 0.001). Significant effects of TRE over time were observed on plasma IGFBP2, insulin, HOMA-IR, and 8-isoprostane levels, without affecting other biomarkers. In the sub-analysis, IGFBP2 increased while leptin and 8-isoprostane decreased significantly only in the "higher weight loss" subgroup. Changes in insulin and HOMA-IR were related to TRE adherence. Eight-week daily 4 to 6 h TRE did not affect IGF1, IGFBP1, or IGFBP3 levels but improved insulin, HOMA-IR, and 8-isoprostane. IGFBP2 increased and leptin decreased when weight loss exceeded 3.5% of baseline.

Unraveling the Impact of Travel on Circadian Rhythm and Crafting Optimal Management Approaches: A Systematic Review.

Circadian rhythms, which regulate essential physiological and behavioral processes, are crucial for maintaining overall health and well-being. However, disruptions to these rhythms, particularly due to trans-meridian travel and shift work, can lead to significant health issues, including jet lag, metabolic imbalances, and neuropsychiatric disorders. In this systematic review, conducted in line withPreferred Reporting Items for Systematic Reviews and Metanalysis (PRISMA) 2020 guidelines, we explore the effectiveness of various interventions aimed at realigning circadian rhythms disrupted by such factors. Focusing on studies published between 2020 and 2024, our search spanned databases like PubMed, Google Scholar, PubMed Central (PMC), and ScienceDirect, emphasizing randomized controlled trials (RCTs), observational studies, and comprehensive reviews. A rigorous quality assessment using the AMSTAR tool for systematic reviews and the SANRA checklist for narrative reviews was employed. Out of an initial 2153 titles, 23 high-quality studies were identified and analyzed. The findings reveal that interventions such as melatonin supplementation, personalized light exposure, and chrono-modulation can significantly improve sleep quality, reduce jet lag symptoms, and promote better health outcomes. This review highlights the critical nature of circadian alignment in preventing serious health issues, such as mental health disorders, metabolic syndromes, and even cancer. It advocates for a personalized, integrative approach that combines melatonin, light therapy, time-restricted eating, exercise, and alternative therapies like electroacupuncture. Such strategies not only facilitate smoother transitions across time zones but also contribute to overall health and resilience. Future studies should aim to assess the long-term benefits and practical applications of these interventions in broader populations.

Development and feasibility testing of a time-restricted eating intervention for women living with overweight/obesity and HIV in a resource-limited setting of South Africa

BackgroundHuman Immunodeficiency Virus (HIV) and type 2 diabetes (T2D) are amongst the leading causes of death in South Africa. The preferred first-line anti-retroviral treatment contains dolutegravir (DTG), shown to increase body weight, may compound the already high rates of obesity and associated risk for T2D. South Africa has widespread food insecurity, making traditional dietary strategies difficult to implement. Time-restricted eating (TRE) may be an appropriate intervention in resource-limited communities.MethodsThis article outlines the development and feasibility testing of a TRE intervention to inform the design of a TRE randomised controlled trial in women (20–45 years old) living with overweight/obesity and HIV, receiving DTG-based treatment from a resource-limited community in Cape Town, South Africa. Factors influencing TRE adoption were identified using the Capability, Opportunity, Motivation – Behaviour model and the Theoretical Domains Framework, combining in-depth interviews (IDIs) and focus group discussions. Participants from the IDIs went on to participate in a single arm 4-week TRE pilot trial where feasibility was explored in terms of reach, acceptability, applicability, and implementation integrity. An iterative, thematic analysis approach was employed to analyse the qualitative data.ResultsParticipants included 33 isiXhosa-speaking women (mean age 37.1 years, mean BMI 35.9 kg/m2). Thematic analysis identified psychological capability (knowledge of fasting), social influences (cultural preferences, family support), and reflective motivation (awareness of weight, health impact, motivation for TRE) as key factors influencing adoption of TRE for weight management. In a 4-week TRE pilot trial (n = 12), retention was 100%. Positive outcomes perceived included improved energy, appetite control and weight loss. TRE was perceived as acceptable, easy, and enjoyable. Family support facilitated adherence, while habitual and social eating and drinking practices were barriers. Compliance was high, aided by self-selected eating times, reminders, and weekly calls. Recommendations included the incorporation of dietary education sessions and text messages to provide additional support and reminders.ConclusionsThis study indicates that TRE is a feasible weight management strategy in women living with overweight/obesity and HIV, receiving DTG-based treatment in a resource-limited community. These findings will ensure that the forthcoming TRE randomised controlled trial is adapted and optimised to the local South African context.

From starvation to time-restricted eating: a review of fasting physiology.

We have long known that subjects with obesity who fast for several weeks survive. Calculations that assume the brain can only use glucose indicated that all carbohydrate and protein sources would be consumed by the brain within several weeks yet subjects with obesity who fasted for several weeks survived. This anomaly led to the determination of the metabolic role of ketone bodies. Subsequent studies transformed our understanding of ketone bodies and illustrated the value of challenging the norm and adapting theory to evidence. Although prolonged fasting is no longer a treatment for obesity, the early studies of starvation provided valuable insights about macronutrient metabolism and ketone body adaptations that fasting elicits. Intermittent fasting and its variants such as time-restricted eating are fasting models that are far less regimented than starvation and severe calorie restriction; yet they produce metabolic benefits. The mechanisms that produce the metabolic changes that intermittent fasting elicits are relatively unknown. In this article, we review the physiology of starvation, starvation adaptation diets, diet-induced ketosis, and intermittent fasting. Understanding the premise and physiology that these regimens induce is necessary to draw parallels and provoke thoughts on the mechanisms underlying the metabolic benefits of intermittent fasting and its variants.

The Effects of Time-Restricted Eating on Fat Loss in Adults with Overweight and Obese Depend upon the Eating Window and Intervention Strategies: A Systematic Review and Meta-Analysis.

A search strategy based on the PICOS principle was used to find relevant publications in seven databases. The outcomes were body composition, anthropometric indicators, and blood lipid metrics. Twenty publications (20 studies) with 1288 participants, covering the period from 2020 to 2024, were included. Compared to the control group, TRE safely and significantly reduced body fat percentage, fat mass, lean mass, body mass, BMI, and waist circumference (MDpooled = -2.14 cm, 95% CI = -2.88~-1.40, p < 0.001), and increased low-density lipoprotein (LDL) (MDpooled = 2.70, 95% CI = 0.17~5.22, p = 0.037), but it did not alter the total cholesterol, high-density lipoprotein, and triglycerides (MDpooled = -1.09~1.20 mg/dL, 95% CI -4.31~5.47, p > 0.05). Subgroup analyses showed that TRE only or TRE-caloric restriction with an eating window of 6 to 8 h may be appropriate for losing body fat and overall weight. This work provides moderate to high evidence that TRE is a promising dietary strategy for fat loss. Although it may potentially reduce lean mass and increase LDL, these effects do not pose significant safety concerns. This trial was registered with PROSPERO as CRD42023406329.

Time-Restricted Eating in Adults With Metabolic Syndrome : A Randomized Controlled Trial.

Time-restricted eating (TRE), limiting daily dietary intake to a consistent 8 to 10 hours without mandating calorie reduction, may provide cardiometabolic benefits. To determine the effects of TRE as a lifestyle intervention combined with current standard-of-care treatments on cardiometabolic health in adults with metabolic syndrome. Randomized controlled trial. (ClinicalTrials.gov: NCT04057339). Clinical research institute. Adults with metabolic syndrome including elevated fasting glucose or hemoglobin A1c (HbA1c; pharmacotherapy allowed). Participants were randomly assigned to standard-of-care (SOC) nutritional counseling alone (SOC group) or combined with a personalized 8- to 10-hour TRE intervention (≥4-hour reduction in eating window) (TRE group) for 3 months. Timing of dietary intake was tracked in real time using the myCircadianClock smartphone application. Primary outcomes were HbA1c, fasting glucose, fasting insulin, homeostasis model assessment of insulin resistance, and glycemic assessments from continuous glucose monitors. 108 participants from the TIMET study completed the intervention (89% of those randomly assigned; 56 women, mean baseline age, 59 years; body mass index of 31.22 kg/m2; eating window of 14.19 hours). Compared with SOC, TRE improved HbA1c by -0.10% (95% CI, -0.19% to -0.003%). Statistical outcomes were adjusted for age. There were no major adverse events. Short duration, self-reported diet, potential for multiple elements affecting outcomes. Personalized 8- to 10-hour TRE is an effective practical lifestyle intervention that modestly improves glycemic regulation and may have broader benefits for cardiometabolic health in adults with metabolic syndrome on top of SOC pharmacotherapy and nutritional counseling. National Institutes of Health.

Summary for Patients: Time-Restricted Eating in Adults With Metabolic Syndrome.

Summary for Patients: Time-Restricted Eating in Adults With Metabolic Syndrome.

Effects of Religious Fasting on Markers of Oxidative Status in Vitamin D-Deficient and Overweight Orthodox Nuns versus Implementation of Time-Restricted Eating in Lay Women from Central and Northern Greece

Background/Objectives: The Mediterranean diet has been widely suggested to exert significant beneficial effects on endothelial oxidative status and cardiometabolic health. Greek Orthodox monasteries, due to their specific nutritional and sartorial habits, comprise a population thatstrictly adheres to nutritional patterns with restricted eating and a plant-based subset of the Mediterranean diet, often accompanied by profound hypovitaminosis D. Time-restricted eating (TRE) is also adopted bya large part of the general lay Greek population for health-promoting reasons, without restrictions on animal product consumption, as imposed by Orthodox religious fasting. However, the comparative effects of these nutritional patterns on oxidative stress markers remain scarce. Methods: The present study attempted to evaluate the effects of Christian Orthodox fasting (COF) in a group of vitamin D-deficient and overweight Orthodox nuns from Central and Northern Greece compared to the implementation of TRE, a 16:8 dietary regimen (16 h of food abstinence and 8 h of feeding) in a cohort of adult women from the general population from the same region with regard to markers of endothelial oxidative status. A group of 50 women from two Orthodox monasteries in Northern Greece and one group of 50 healthy lay women were included. During the enrollment, a detailed recording of their dietary habits was performed, along with a scientific registry of their demographic and anthropometric characteristics (via bioimpedance). The Orthodox nuns followed a typical Orthodox fasting regimen [daily feeding window (8 a.m.–4 p.m.)], whereas the lay women followed a TRE 16:8 regimen with the same feeding time-window with a recommendation to follow a low-fat diet, without characteristics of the Mediterranean diet. We included a complete biochemical analysis, as well as calciotropic profiles [calcium—Ca, albumin, parathyroid hormone—PTH, and 25-hydroxyvitamin D—25(OH)D] and markers of TAC (total antioxidant capacity), GSH (glutathione),and thiobarbituric acid reactive substances (TBARSs) concentrations as markers of oxidative status. Results: All the groups were compared at the baseline regarding their calcium, PTH, and 25(OH)D concentrations, with no statistically significant differences between the groups apart from higher PTH levels in the nuns due to lower 25(OH)D levels. The Orthodox nuns manifested a lower median GSH compared to the controls (6.0 vs. 7.2, p 0.04) and a higher median TAC (0.92 vs. 0.77, p &lt; 0.001). The TBARS comparisons showed no significant difference between the two groups. No significant associations of oxidative status with 25(OH)D, PTH, and the markers of glucose homeostasis were evident. Conclusions: The results of this small pilot study indicate that both dietary regimens have advantages over the oxidative markers compared to each other, with increased TAC in the group of Orthodox nuns after a 16-week period of COF compared to a 16:8 TRE and increased GSH concentrations in the lay women group. Future randomized trials are required to investigate the superiority or non-inferiority between these dietary patterns in the daily clinical setting.

A randomized feasibility trial of time-restricted eating during pregnancy in people with increased risk of gestational diabetes

Time-restricted eating (TRE) is a nutritional intervention that confines the daily time-window for energy intake. TRE reduces fasting glucose concentrations in non-pregnant individuals, but whether this eating protocol is feasible and effective for glycemic control in pregnancy is unknown. The aim of this randomized controlled trial was to investigate the adherence to and effect of a 5-week TRE intervention (maximum 10 h daily eating window) among pregnant individuals at risk of gestational diabetes mellitus (GDM), compared with a usual-care control group. Participants underwent 2-h oral glucose tolerance tests and estimation of body composition, before and after the intervention. Interstitial glucose levels were continuously measured, and adherence rates and ratings of hunger were recorded daily. Thirty of 32 participants completed the trial. Participants allocated to TRE reduced their daily eating window from 12.3 (SD 1.3) to 9.9 (SD 1.0) h, but TRE did not affect glycemic measures, blood pressure, or body composition, compared with the control group. TRE increased hunger levels in the evening, but not in the morning, and induced only small changes in dietary intake. Adhering to a 5-week TRE intervention was feasible for pregnant individuals with increased risk of GDM but had no effect on cardiometabolic outcomes.