Time-Restricted Eating Without Calorie Counting for Weight Loss in a Racially Diverse Population : A Randomized Controlled Trial.

BACKGROUND: Time-restricted eating (TRE), without calorie counting, has become a popular weight loss strategy, yet long-term randomized trials evaluating its efficacy are limited. OBJECTIVE: To determine whether TRE is more effective for weight control and cardiometabolic risk reduction compared with calorie restriction (CR) or control. DESIGN: 12-month randomized controlled trial. (ClinicalTrials.gov: NCT04692532). SETTING: University of Illinois Chicago from January 2021 to September 2022. PARTICIPANTS: 90 adults with obesity. INTERVENTION: 8-hour TRE (eating between noon and 8:00 p.m. only, without calorie counting), CR (25% energy restriction daily), or control (eating over a period of 10 or more hours per day). Participants were not blinded. MEASUREMENTS: Change in body weight, metabolic markers, and energy intake by month 12. RESULTS: Seventy-seven persons completed the study. Mean age was 40 years (SD, 11), 33% were Black, and 46% were Hispanic. Mean reduction in energy intake was -425 kcal/d (SD, 531) for TRE and -405 kcal/d (SD, 712) for CR. Compared with the control group, weight loss by month 12 was -4.61 kg (95% CI, -7.37 to -1.85 kg; P ≤ 0.01) (-4.87% [CI, -7.61% to -2.13%]) for the TRE group and -5.42 kg (CI, -9.13 to -1.71 kg; P ≤ 0.01) (-5.30% [CI, -9.06% to -1.54%]) for the CR group, with no statistically significant difference between TRE and CR (0.81 kg [CI, -3.07 to 4.69 kg; P = 0.68]) (0.43% [CI, -3.48% to 4.34%]). LIMITATION: Not blinded, not powered to detect relatively large differences in weight loss, and lack of adjustment for multiple comparisons. CONCLUSION: Time-restricted eating is more effective in producing weight loss when compared with control but not more effective than CR in a racially diverse population. PRIMARY FUNDING SOURCE: National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases.

Current research: effect of time restricted eating on weight and cardiometabolic health.

Intermittent fasting has grown in popularity as a weight loss strategy in recent years. In particular, time restricted eating (TRE) has been popularized in the diet industry with dozens of books touting its ability to promote weight loss and improve glucose regulation. TRE involves confining the eating window to a specified number of hours per day (usually 4-10 h), and fasting (with zero-calorie beverages) for the remaining hours of the day. While several studies of TRE have been performed in rodent models, human studies are only now emerging. The goal of this review is to summarize the effects of TRE on body weight and cardiometabolic disease risk factors in human subjects. Accumulating evidence shows that TRE may spontaneously decrease energy intake by 20-30% under ad libitum conditions, producing small but statistically significant weight loss of 1-4%. In addition, TRE may significantly decrease systolic and diastolic blood pressure independent of weight loss. Further, improvements in fasting insulin and insulin resistance have also been reported. Taken together, these preliminary data suggest that TRE produces mild weight loss, and also may improve some aspects of cardiometabolic health by lowering blood pressure and insulin resistance.

Time restricted eating for the prevention of type 2 diabetes.

Type 2 diabetes can potentially be prevented by targeted lifestyle and weight loss interventions. Time restricted eating (TRE) is a form of intermittent fasting that has emerged as a novel diet strategy to reduce body weight and improve glycaemic control. TRE involves eating within a certain window of time (usually 4 to 10 h), and water-fasting for the remaining hours of the day. The purpose of this review is to summarize the effects of TRE on body weight and markers of glycaemic control in human subjects. We also aim to provide mechanistic insights into the effect of TRE on insulin sensitivity and glucose tolerance. Results to date reveal that TRE produces mild weight loss (1%-4% from baseline) and energy restriction, when food consumption is restricted to 4-10 h/day. TRE also reduces fasting insulin and improves insulin sensitivity in individuals with prediabetes and those with obesity. Moreover, TRE improves glucose tolerance and decreases serum glucose excursions. The possible mechanisms underlying these benefits include increased autophagic flux, mild elevations in ketone bodies, a reduction in oxidative stress, and the stimulation of ß-cell responsiveness. While these preliminary results offer promise for the use of TRE in the prevention of type 2 diabetes, larger and longer-term human trials will be needed to confirm these findings.

Cardiometabolic Benefits of Intermittent Fasting.

This review aims to summarize the effects of intermittent fasting on markers of cardiometabolic health in humans. All forms of fasting reviewed here-alternate-day fasting (ADF), the 5:2 diet, and time-restricted eating (TRE)-produced mild to moderate weight loss (1-8% from baseline) and consistent reductions in energy intake (10-30% from baseline). These regimens may benefit cardiometabolic health by decreasing blood pressure, insulin resistance, and oxidative stress. Low-density lipoprotein cholesterol and triglyceride levels are also lowered, but findings are variable. Other health benefits, such as improved appetite regulation and favorable changes in the diversity of the gut microbiome, have also been demonstrated, but evidence for these effects is limited. Intermittent fasting is generally safe and does not result in energy level disturbances or increased disordered eating behaviors. In summary, intermittent fasting is a safe diet therapy that can produce clinically significant weight loss (>5%) and improve several markers of metabolic health in individuals with obesity.

The effect of 4-h versus 6-h time restricted feeding on sleep quality, duration, insomnia severity and obstructive sleep apnea in adults with obesity.

BACKGROUND: Time restricted feeding (TRF) involves deliberately restricting the times during which energy is ingested. Preliminary findings suggest that 8-10-h TRF improves sleep. However, the effects of shorter TRF windows (4-6 h) on sleep, remain unknown. AIMS: This study compared the effects of 4-h versus 6-h TRF on sleep quality, duration, insomnia severity and the risk of obstructive sleep apnea. METHODS: Adults with obesity (n = 49) were randomized into one of three groups: 4-h TRF (eating only between 3 and 7 p.m.), 6-h TRF (eating only between 1 and 7 p.m.), or a control group (no meal timing restrictions) for 8 weeks. RESULTS: After 8 weeks, body weight decreased (p < 0.001) similarly by 4-h TRF (-3.9 ± 0.4 kg) and 6-h TRF (-3.4 ± 0.4 kg), versus controls. Sleep quality, measured by the Pittsburgh Sleep Quality Index (PSQI), did not change by 4-h TRF (baseline: 5.9 ± 0.7; week 8: 4.8 ± 0.6) or 6-h TRF (baseline: 6.4 ± 0.8; week 8: 5.3 ± 0.9), versus controls. Wake time, bedtime, sleep duration and sleep onset latency also remained unchanged. Insomnia severity did not change by 4-h TRF (baseline: 4.4 ± 1.0; week 8: 4.7 ± 0.9) or 6-h TRF (baseline: 8.3 ± 1.2; week 8: 5.5 ± 1.1), versus controls. Percent of participants reporting obstructive sleep apnea symptoms did not change by 4-h TRF (baseline: 44%; week 8: 25%) or 6-h TRF (baseline: 47%; week 8: 20%), versus controls. CONCLUSION: These findings suggest that 4- and 6-h TRF have no effect on sleep quality, duration, insomnia severity, or the risk of obstructive sleep apnea.

Time-Restricted Eating to Improve Cardiovascular Health.

PURPOSE OF REVIEW: Time-restricted eating (TRE) is a form of intermittent fasting that involves confining the eating window to 4-10 h and fasting for the remaining hours of the day. The purpose of this review is to summarize the current literature pertaining to the effects of TRE on body weight and cardiovascular disease risk factors. RECENT FINDINGS: Human trial findings show that TRE reduces body weight by 1-4% after 1-16 weeks in individuals with obesity, relative to controls with no meal timing restrictions. This weight loss results from unintentional reductions in energy intake (~350-500 kcal/day) that occurs when participants confine their eating windows to 4-10 h/day. TRE is also effective in lowering fat mass, blood pressure, triglyceride levels, and markers of oxidative stress, versus controls. This fasting regimen is safe and produces few adverse events. These findings suggest that TRE is a safe diet therapy that produces mild reductions in body weight and also lowers several key indicators of cardiovascular disease in participants with obesity.

Does the weight loss efficacy of alternate day fasting differ according to sex and menopausal status?

BACKGROUND AND AIMS: This study examined if the weight loss and metabolic benefits of alternate day fasting (ADF) varies according to sex and menopausal status in adults with obesity. METHODS AND RESULTS: This secondary analysis pooled the data of men and women (n = 75) who participated in three 12-week ADF studies (500 kcal fast day; alternated with an ad libitum intake feast day). Body weight decreased in premenopausal women (-4.6 ± 3.2%), postmenopausal women (-6.5 ± 3.2%) and men (-6.2 ± 4.4%) (main effect of time, P < 0.001), with no difference between groups (no group × time interaction). Energy intake on fast days was higher than prescribed in all groups (∼400-500 excess kcal consumed), with no differences between groups. Fat mass, lean mass, fasting insulin, and insulin resistance, and blood pressure decreased similarly in all groups (main effect of time, P < 0.05 for all comparisons). LDL cholesterol decreased more in postmenopausal versus premenopausal women (group × time interaction, P = 0.01). Fasting glucose, HDL cholesterol, and triglycerides remained unchanged in all groups. CONCLUSION: These findings suggest that the weight loss and metabolic benefits of ADF do not generally vary according to sex or menopausal status in adults with obesity. TRIAL REGISTRATION: Clinicaltrials.gov, NCT00960505; NCT03528317.

Effect of time restricted feeding on the gut microbiome in adults with obesity: A pilot study.

BACKGROUND: Time restricted feeding is a form of intermittent fasting where participants shorten the daily window in which they eat. AIM: This is the first study to examine the effects of intermittent fasting on changes in the gut microbiome. METHODS: Adults with obesity (n = 14) participated in a daily 8-hour time restricted feeding intervention (8-hour feeding window/16-hour fasting window) for 12 weeks. Fecal microbiota were determined by 16 S rRNA (ribosomal ribonucleic acid) gene sequencing of stool samples. RESULTS: Body weight decreased (P < 0.05) by -2 ± 1 kg. Gut microbiota phylogenetic diversity remained unchanged. The two most common phyla were Firmicutes and Bacteroidetes accounting for 61.2% and 26.9% of total abundance at baseline. No significant alterations in the abundance of Firmicutes, Bacteroidetes, or any other phyla were detected after 12 weeks of time restricted feeding. CONCLUSIONS: Time restricted feeding did not significantly alter the diversity or overall composition of the gut microbiome.

Beverage intake during alternate-day fasting: Relationship to energy intake and body weight.

BACKGROUND: Alternate-day fasting (ADF) involves a 'famine day' (25% energy intake) and a 'feast day' (ad libitum intake). This secondary analysis examined changes in beverage intake in relation to energy intake and body weight during 12 months of ADF versus daily calorie restriction (CR). METHODS: Obese subjects (n = 100 enrolled, n = 69 completers) were randomized to one of three groups for 12 months: (a) ADF; (b) CR; or (c) control. RESULTS: At baseline, intakes of diet soda, caffeinated beverages, sugar-sweetened soda, alcohol, juice, and milk were similar between groups. There were no statistically significant changes in the intake of these beverages by month 6 or 12 between ADF (feast or famine day), CR, or control groups. Beverage intake was not related to energy intake or body weight at month 6 or 12 in any group. CONCLUSION: These pilot findings suggest that intermittent fasting does not impact beverage intake in a way that affects energy intake or body weight.

Eating behavior traits of successful weight losers during 12 months of alternate-day fasting: An exploratory analysis of a randomized controlled trial.

BACKGROUND: Alternate-day fasting (ADF) has gained popularity in recent years. The diet consists of a "fast day" where an individual consumes 0-25% of their energy needs, alternated with a "feast day" where a person is permitted to eat ad libitum. AIM: This study examined eating behavior traits of successful weight losers during alternate day fasting. METHODS: Obese participants ( n = 34) took part in 12 months of ADF and were grouped into a high (≥5%) or low-weight-loss (<5%) group post-treatment. RESULTS: The high-weight-loss group demonstrated increased ( p = 0.04) fullness, decreased ( p = 0.03) hunger, increased dietary protein intake (15% to 20% of kcal, p = 0.04), and better adherence to fast-day calorie goals. CONCLUSIONS: Thus, individuals who achieve clinically significant weight loss with ADF demonstrate improved satiety, increased protein intake, and better adherence to fast-day calorie goals.

Efficacy and safety of prolonged water fasting: a narrative review of human trials.

The goal of this narrative review is to summarize the effects of prolonged fasting on various metabolic health measures, including body weight, blood pressure, plasma lipids, and glycemic control. Prolonged fasting is characterized by consciously eating little to no food or caloric beverages for several days to weeks. Results reveal that prolonged fasting for 5-20 days produces potent increases in circulating ketones, and mild to moderate weight loss of 2-10%. Approximately two-thirds of the weight lost is lean mass, and one-third is fat mass. The excessive lean mass loss suggests that prolonged fasting may increase the breakdown of muscle proteins, which is a concern. Systolic and diastolic blood pressure consistently decreased with prolonged fasting. However, the impact of these protocols on plasma lipids is less clear. While some trials demonstrate decreases in LDL cholesterol and triglycerides, others show no benefit. With regard to glycemic control, reductions in fasting glucose, fasting insulin, insulin resistance, and glycated hemoglobin (HbA1c) were noted in adults with normoglycemia. In contrast, these glucoregulatory factors remained unchanged in patients with type 1 or type 2 diabetes. The effects of refeeding were also examined in a few trials. It was shown that 3-4 months after the fast was completed, all metabolic benefits were no longer observed, even when weight loss was maintained. With regard to adverse events, metabolic acidosis, headaches, insomnia, and hunger were observed in some studies. In summary, prolonged fasting appears to be a moderately safe diet therapy that can produce clinically significant weight loss (>5%) over a few days or weeks. However, the ability of these protocols to produce sustained improvements in metabolic markers warrants further investigation.

Time-restricted eating: Watching the clock to treat obesity.

Time-restricted eating (TRE) has become a popular strategy to treat obesity. TRE involves confining the eating window to 4-10 h per day and fasting for the remaining hours (14-20 h fast). During the eating window, individuals are not required to monitor food intake. The sudden rise in popularity of TRE is most likely due to its simplicity and the fact that it does not require individuals to count calories to lose weight. This feature of TRE may appeal to certain individuals with obesity, and this could help produce lasting metabolic health improvements. The purpose of this review is to summarize current evidence from randomized clinical trials of TRE (without calorie counting) on body weight and metabolic risk factors. The efficacy of TRE in various populations groups, including those with obesity, type 2 diabetes (T2DM), and polycystic ovary syndrome (PCOS), is also examined.

Impact of Diet Modifications on Body Weight, Body Composition, Treatment Outcomes, and Quality of Life During Primary Treatment for Breast Cancer: A Systematic Review.

CONTEXT: Breast cancer is a significant public health challenge, with 290 000 new cases annually and significant healthcare costs. Treatment advancements have led to improvements in survival, but common adverse effects include weight gain, fatigue, nausea, and taste changes, decreasing quality of life. OBJECTIVE: This review aims to assess the impact of diet and lifestyle interventions during primary treatment for breast cancer and their effects on body weight, body composition, treatment-related adverse outcomes, and patient-reported quality of life. DATA SOURCES AND DATA EXTRACTION: A search of PubMed, CINAHL, and EMBASE conducted through May 10, 2023, identified 31 publications describing 27 interventions including diet or diet plus exercise. The Cochrane Risk of Bias tool assessed the quality of publications. DATA ANALYSIS: The findings suggest that whole foods, aerobic and strength-training exercises, and intermittent fasting during treatment may improve body weight and composition, treatment-related outcomes, and quality of life. Limitations include variation in study duration, small sample sizes, and limited sociodemographic data. CONCLUSION: Improvements seen with increased diet quality and reduced caloric intake, with or without exercise, challenge current standard-of-care recommendations during treatment for breast cancer. While there is a need for additional research, healthcare teams can confidently promote healthy diets and exercise during primary treatment for breast cancer to manage weight and improve treatment-related side effects and quality of life. SYSTEMATIC REVIEW REGISTRATION: PROSPERO registration no. 42023425613.

A Narrative Review of Intermittent Fasting With Exercise.

Intermittent fasting is a dietary pattern that encompasses the 5:2 diet, alternate-day fasting, and time-restricted eating. All 3 involve alternating periods of fasting and ad libitum eating. Like other dietary strategies, intermittent fasting typically induces loss of both fat mass and lean mass. Exercise may thus be a useful adjuvant to promote lean mass retention while adding cardiometabolic, cognitive, mental, and emotional health improvements. In this narrative review, we summarize current evidence regarding the combination of intermittent fasting and exercise and its influence on body weight, body composition, cardiometabolic risk, and muscular and cardiorespiratory fitness. A PubMed search was conducted to identify all trials lasting >4 weeks that combined 5:2 diet, alternate-day fasting, or time-restricted eating with any modality exercise and had body weight as an end point. A total of 23 trials (26 publications) were identified. Evidence suggests that combining intermittent fasting with exercise leads to decreased fat mass regardless of weight status. However, evidence is equivocal for the influence on other aspects of weight loss and body composition, fat-free mass, and cardiometabolic risk factors and may be dependent on weight status or exercise doses (ie, frequency, intensity, duration, and modality). Higher-powered trials are needed to determine the efficacy of combining exercise and intermittent fasting for benefits on body weight and cardiometabolic risk. Current evidence suggests that intermittent fasting does not impair adaptation to exercise training, and may improve explosive strength, endurance, and cardiopulmonary measures such as maximal oxygen consumption. In addition, we discuss limitations in the current evidence base and opportunities for continued investigation. Future trials in this area should consider interventions that have increased sample size, longer intervention duration, broadened inclusion criteria, objective measures of diet and exercise adherence, and diversity of sample population.

Design of a Remote Time-Restricted Eating and Mindfulness Intervention to Reduce Risk Factors Associated with Early-Onset Colorectal Cancer Development among Young Adults.

Early-onset colorectal cancer (EOCRC) is defined as a diagnosis of colorectal cancer (CRC) in individuals younger than 50 years of age. While overall CRC rates in the United States (US) decreased between 2001 and 2018, EOCRC rates have increased. This research project aims to evaluate the feasibility and acceptability of Time-Restricted Eating (TRE), Mindfulness, or TRE combined with Mindfulness among young to middle-aged adults at risk of EOCRC. Forty-eight participants will be randomly assigned to one of four groups: TRE, Mindfulness, TRE and Mindfulness, or Control. Data on feasibility, adherence, and acceptability will be collected. Measures assessed at baseline and post-intervention will include body weight, body composition, dietary intake, physical activity, sleep behavior, circulating biomarkers, hair cortisol, and the gut microbiome. The effects of the intervention on the following will be examined: (1) acceptability and feasibility; (2) body weight, body composition, and adherence to TRE; (3) circulating metabolic, inflammation, and oxidative stress biomarkers; (4) intestinal inflammation; and (5) the gut microbiome. TRE, combined with Mindfulness, holds promise for stress reduction and weight management among individuals at risk of EOCRC. The results of this pilot study will inform the design and development of larger trials aimed at preventing risk factors associated with EOCRC.

Effect of Time-Restricted Eating on Sleep in Type 2 Diabetes.

The aim of this secondary analysis was to compare the effects of time-restricted eating (TRE) versus calorie restriction (CR) and controls on sleep in adults with type 2 diabetes (T2D). Adults with T2D (n = 75) were randomized to 1 of 3 interventions for 6 months: 8 h TRE (eating only between 12 and 8 pm daily); CR (25% energy restriction daily); or control. Our results show that TRE has no effect on sleep quality, duration, insomnia severity, or risk of obstructive sleep apnea, relative to CR and controls, in patients with T2D over 6 months.

International consensus on fasting terminology.

Although fasting is increasingly applied for disease prevention and treatment, consensus on terminology is lacking. Using Delphi methodology, an international, multidisciplinary panel of researchers and clinicians standardized definitions of various fasting approaches in humans. Five online surveys and a live online conference were conducted with 38 experts, 25 of whom completed all 5 surveys. Consensus was achieved for the following terms: "fasting" (voluntary abstinence from some or all foods or foods and beverages), "modified fasting" (restriction of energy intake to max. 25% of energy needs), "fluid-only fasting," "alternate-day fasting," "short-term fasting" (lasting 2-3 days), "prolonged fasting" (≥4 consecutive days), and "religious fasting." "Intermittent fasting" (repetitive fasting periods lasting ≤48 h), "time-restricted eating," and "fasting-mimicking diet" were discussed most. This study provides expert recommendations on fasting terminology for future research and clinical applications, facilitating communication and cross-referencing in the field.

Alternate-Day Fasting Combined with Exercise: Effect on Sleep in Adults with Obesity and NAFLD.

Objective: This study investigated how alternate-day fasting (ADF) combined with aerobic exercise impacts body weight and sleep in adults with non-alcoholic fatty liver disease (NAFLD). Methods: Adults with obesity and NAFLD (n = 80) were randomized into one of four groups for 3 months: combination of ADF (600 kcal "fast day," alternated with an ad libitum intake "feast day") and moderate-intensity aerobic exercise (five sessions per week, 60 min/session); ADF alone; exercise alone; or a no-intervention control group. Results: By month 3, body weight and intrahepatic triglyceride content decreased (p < 0.001, group × time interaction) in the combination group versus the exercise group and control group, but not versus the ADF group. Sleep quality, measured by the Pittsburgh Sleep Quality Inventory (PSQI), did not change in the combination group (baseline: 6.0 ± 0.7; month 3: 5.6 ± 0.7), ADF group (baseline: 8.9 ± 1.0; month 3: 7.5 ± 0.8), or exercise group (baseline: 6.4 ± 0.6; month 3: 6.7 ± 0.6), versus controls (baseline: 5.5 ± 0.7; month 3: 4.6 ± 0.5). Wake time, bedtime, sleep duration, and insomnia severity did not change (no group x time interaction) over the course of the study in any group. Risk for obstructive sleep apnea was present in 30% of combination subjects, 75% of ADF subjects, 40% of exercise subjects, and 75% of controls, and did not change in the intervention groups, versus controls, by month 3. No associations were observed between changes in body weight, intrahepatic triglyceride content, and any sleep outcome. Conclusions: The weight loss induced by ADF combined with exercise does not improve sleep quality, duration, insomnia severity, or risk of obstructive sleep apnea in individuals with NAFLD.

Protocol for measuring intrahepatic triglyceride content in adults with non-alcohol fatty liver disease.

Here, we present a protocol for conducting magnetic resonance imaging proton density fat fraction (MRI-PDFF) to measure intrahepatic triglyceride (IHTG) content in adults with non-alcohol fatty liver disease (NAFLD). We describe steps for screening patients for NAFLD, MRI-PDFF scanning, and using MRI-PDFF data to quantify IHTG. This protocol can be repeated sequentially and used in weight loss trials. However, it is limited to patients with NAFLD as it does not assess non-alcoholic steatohepatitis or hepatic fibrosis. For complete details on the use and execution of this protocol, please refer to Ezpeleta et al. (2023).1.

Effect of time-restricted eating on sex hormone levels in premenopausal and postmenopausal females.

OBJECTIVE: Concerns have been raised regarding the impact of time-restricted eating (TRE) on sex hormones in females. This study examined how TRE affects sex steroids in premenopausal and postmenopausal females. METHODS: This is a secondary analysis of an 8-week TRE study (4- to 6-hour eating window) conducted in adults with obesity. Men and perimenopausal females were excluded. Females were classified into two groups based on menstrual status: premenopausal (n = 12) or postmenopausal (n = 11). RESULTS: After 8 weeks, body weight decreased in premenopausal females (-3% ± 2%) and postmenopausal females (-4% ± 2%) (main effect of time, p < 0.001), with no difference between groups (no group × time interaction). Circulating levels of testosterone, androstenedione, and sex hormone binding globulin (SHBG) did not change in either group (no group × time interaction). Dehydroepiandrosterone (DHEA) concentrations decreased (p < 0.05) in premenopausal (-14% ± 32%) and postmenopausal females (-13% ± 34%; main effect of time, p = 0.03), with no difference between groups. Estradiol, estrone, and progesterone were measured only in postmenopausal females, and they remained unchanged. CONCLUSIONS: In premenopausal females, androgens and SHBG remained unchanged during TRE, whereas DHEA decreased. In postmenopausal females, estrogens, progesterone, androgens, and SHBG did not change, but DHEA was reduced.