Table 4.
A summary of human studies investigating the impact of time-restricted eating in humans and metabolic health outcomes.
| Time-Restricted Feeding (TRF) | |||||
|---|---|---|---|---|---|
| Participants | Eating Restrictions | Study Type/Duration | Health Outcomes | Energy Intake | Reference |
| n = 49 obese subjects BMI 30–50 kg/m2 | Eating window of 4 h (3 pm–7 pm) vs. 6 h (1 pm–7 pm) vs. controls (7 am–7 pm) | Randomized parallel-arm trial over 8 weeks | Both TRF regimens showed reduction in body weight, insulin resistance, oxidative stress levels. Four-hour TRE did not result in greater weight loss compared to six-hour TRE. | Reduction in energy intake by 550 kcal/day in both cases without calorie counting | [176] |
| n = 11 Obese sedentary males BMI: 30.2–34.2 kg/m2 | Eating window 10 am–5 pm vs. 7 am–9 pm | Randomized crossover trial; 3 weeks each intervention of 5 days with 10 days washout period | Improved glycaemic control and decrease in evening hunger | Isocaloric intake | [177] |
| n = 19 with T2D BMI: 29–39 kg/m2 | 4-week TRE 10 am–7 pm | non-randomised 2-week baseline, 4-week intervention | Compliance 72 ± 24%, no improvement in glycaemic control or body mass | Isocaloric intake | [178] |
| n = 23 obese subjects BMI 30 and 45 kg/m2 | Eating over 8-h window (10 am–6 pm) vs. ad libitum eating | 2-week baseline intake, 12-week intervention | Time-restricted eating showed reduction in body weight and systolic blood pressure | Decreases caloric intake by ~300 kcal/d | [179] |
| n = 34 resistance-trained weight 84.6 ± 6.2 kg | TRF (1 pm–8 pm) vs. control (8 am–8 pm) | Randomized parallel-arm trial over 8 weeks | TRF only showed a reduction in fat mass but no other metabolic parameters were altered. Fat free mass and muscle mass area in arm and thigh remain unchanged | Isocaloric intake | [180] |
| n = 9 overweight sedentary older adults BMI 25–40 kg/m2 | 16 h fast (14–18 h range) | Baseline assessment followed by 4-week intervention | TRE resulted in short-term weight loss and improved waist circumference, cognitive and physical function and health-related quality of life | No data available | [181] |
| n = 8, prediabetic BMI 32.2 ± 4.4 kg/m2 | eTRF; 6-h eating period and dinner before 3 pm for 5 weeks, vs. 12-h eating period | Randomized crossover trial for 17 weeks, each intervention 5 weeks | eTRF reduced insulin levels and improved insulin sensitivity, lowered blood pressure; reduction in oxidative stress and appetite in the evening. | Isocaloric intake | [182] |
| n = 19 with metabolic syndrome | Eating over self-selected 10-h window | 2-week baseline intake, 12-week intervention | TRE improves cardiometabolic health (reduction in weight, BMI, waist circumference, percentage body fat, systolic and diastolic blood pressure, improved lipid parameters, glucose and insulin homeostasis | Decreases caloric intake | [183] |
| n = 8 overweight BMI > 25 kg/m2 | Eating over self-selected 10-h window | 3-week baseline intake, 16-week | Reduction in body weight. Significant improvement in sleep, hunger at bedtime, energy levels | Reduced estimated energy intake by 20–26% | [170] |
| n = 11, BMI 25.0 and 35.0 kg/m2 | eTRF (8 am to 2 pm) vs. control (8 am to 8 pm) | Randomized crossover 4-day intervention, 3.5–5 weeks’ washout period between interventions | eTRF improves 24-hour glucose levels, alters lipid metabolism and expression of SIRT1 and LC3A (autophagy gene), BDNF (a neurotrophic factor promoting neuronal growth) and mTOR | Isocaloric intake | [184] |
| n = 11 overweight BMI 25–35 kg/m2 | eTRF (8 am–2 pm) vs. control (8 am–8 pm) | Randomized crossover 4-day intervention, 3.5–5 weeks’ washout period between interventions | Meal-timing interventions facilitate weight loss primarily by decreasing appetite rather than by increasing energy expenditure. eTRF may also increase fat loss by increasing fat oxidation. | Isocaloric | [185] |
| n = 21 healthy adults BMI 29.6 ± 2.6 kg/m2 | TRE (12 pm to 8 pm) vs. control eating habits with concomitant aerobic exercise for 8 weeks | Randomized, controlled trial | TRF individuals lost significantly more body mass (3.3% vs. 0.2%) and fat mass (9% vs. 3.3%). Lean mass increased but no significant difference between the groups. | Reduction in caloric intake in TRE (~300 kCal/day) | [186] |
| n = 27 BMI 21.9–26.9 kg/m2 | TRE included an elimination of caloric intake between 7 pm and 6 am vs. controls | Crossover 2-week intervention with one-week washout period | TRE led to a loss in small amount of body weight | Reduction in energy (~240 Kcal) and fat intake un TRE group | [187] |
| n = 18 Body weight 79.0 ± 13.5 kg in control group and 87.4 ± 19.2 in TRE group | TRE (eating over any 4-h window between 4 pm and 12 pm on the four days a week when they exercised but ad libitum on days without exercise) vs. control without any restrictions | Randomized controlled trial 8 weeks | No significant loss of body weight, no adverse effect on lean mass retention or muscular improvements. | TRF reduced caloric intake by ~667 kCal a day | [188] |
| n = 13 BMI 20–39 kg/m2 | TRF with delayed breakfast and advanced dinner by 1.5 h vs. controls with habitual eating patterns | 2-week baseline, 10 weeks’ intervention | No significant reduction in weight, but reduction in adiposity, fasting glucose observed | Reduction in energy intake in TRE group | [189] |
| n = 40 resistance-trained females Body weight 57.1 to 73.4 Kg | Control diet vs. TRF (12 pm–8 pm) vs. TRF+ a leucine metabolite β-hydroxy β-methyl butyrate (HMB) supplementation | randomized, placebo-controlled for 8 weeks | TRF did not produce changes in physiological variables including resting metabolic rate, substrate utilization, blood lipids, glucose and insulin, blood pressure, arterial stiffness, or cortisol responses. No significant difference in physical performance. | No significant variation between the groups | [190] |
| n = 40 with abdominal obesity BMI 25.1–37.6 kg/m2 | TRF eating window 8–9 h | 3-month single arm trial | Moderate weight loss, improved waist circumference, HbA1C | No data available | [191] |
| n = 22 men BMI: 28.5 ± 8.3 kg/m2 | Isocaloric TRF (8-h eating window, caloric intake within 300 Kcal of habitual intake) vs. ad libitum TRF (8-h eating window but no restriction on calories) | 28 days randomised control trial | Decrease in body mass, decrease in fat body mass, decrease in BP and increase in HDLC in both groups. | No significant difference in caloric intake | [192] |
| n = 20 obese BMI 34.1± 7.5 kg/m2 | TRE (self-selected 8-h eating window) vs. control on ad libitum | 12 weeks | Decrease in eating frequency, weight, lean mass, visceral fat | No data reported | [193] |
| n = 116 overweight and obese BMI 27.4–35.4 kg/m2 | TRE (12–8 pm) eating vs. ad libitum | 12 weeks’ randomised control trial | Loss of body weight in TRE group | No significant difference in caloric intake | [194] |
| n = 271 NAFLD BMI > 24 kg/m2 | Control vs. ADF (25% energy intake on fast days) vs. TRF (self-directed 8-hour window) | 12 weeks’ randomised control trial | Significant weight loss and fat mass loss, reduction in cholesterol and triglycerides both in ADF and TRF with ADF achieving better outcomes | No significant difference in caloric intake | [195] |
| n = 15 PCOS women BMI ≥ 24 kg/m2 | TRE (8 am–4 pm) | Non-randomized 1 week baseline, 5 weeks’ intervention | Reduction in body weight, BMI, body fat mass, body fat percentage, improved insulin sensitivity | Isocaloric | [196] |
| n = 22 BMI = 24.7 ± 0.6 kg/m2 | TRE (eating within 8-h window but first meal between 10–11 am) vs. controls with normal feeding patterns | Randomized controlled trial, 1 week baseline, 6-week intervention | No weight loss or improvement in cardiovascular function with modest improvement in functional endurance and glucose tolerance, 84–95% adherence | Isocaloric | [197] |
| n = 60 BMI ≥ 30 kg/m2 | 14:10 TRE (14-h metabolic fast with snack with 200 kcal mixed nuts 12 h after the fast started) vs. 12:12 TRE (12-h fast without any snack) | Randomized controlled trial 8 weeks intervention | Weight loss observed in both cases but more in 14 h metabolic fast group, improved fasting blood glucose. Fasting snack decreased hunger | 500–1000 kcal deficit each day | [198] |
| n = 45 with at least one metabolic syndrome component and usual eating window of 14 h. BMI ≥ 20 kg/m2 | TRE (self-selected window of 12 h) vs. no restriction | Randomised control trial 4 weeks’ baseline, 6-month intervention | No significant difference in weight loss | No difference reported | [199] |
| n = 80 males | TRF (8-h eating window, 7.30 pm–3.30 am) vs. normal diet daily fasting for 16 h for 25 days | 25 Days | TRF improved lipid parameters, reduced inflammatory markers, enhanced gut microbial richness with enrichment of Prevotellaceae and Bacteroideaceae; activated SIRT1 | No data available | [200] |
| Time-restricted feeding (TRF) vs. Continuous caloric restriction (CR) | |||||
| n = 16 BMI 24.0 ± 0.6 kg/m2 | eTRF (8 am till 4 pm) vs. control on caloric restriction | Non-randomised 1-week baseline, 2 weeks’ intervention | eTRF improved insulin sensitivity, glucose uptake, reduction in energy intake and weight loss | Isocaloric | [201] |
| n = 37 overweight BMI 26.4–28.55 kg/m2 | TRE (8 am–4 pm) vs. BMI matched participants on hypocaloric diet based on orthodox fasting | Both groups showed reduction in BMI and fasting group also showed a reduction in total and LDL cholesterol | Isocaloric | [202] | |
| Early time-restricted feeding (eTRF) vs. late time-restricted feeding (lTRF) | |||||
| n = 15 men at risk of T2D BMI 33.9 ± 0.8 kg/m2 | eTRF (8 am–5 pm) vs. late TRF (12 pm–9 pm) over 2-time 7-day TRF with 2 weeks’ washout period | Randomised crossover trial, 1-week baseline, 1-week intervention, 2 weeks’ washout period | Both TRF regimens showed reductions in body weight, glycaemic responses to a test meal, triglycerides. | No data available | [203] |
| n = 82 BMI 18.6–25.8 kg/m2 | Early TRF (6 am–3 pm) vs. mid-day TRF (11 an–8 pm) vs. controls | Randomised control trial, 5 weeks’ intervention | Early TRF was more effective in improving insulin sensitivity, fasting glucose, reduction in body mass and adiposity, reduction in inflammation and increased gut microbial diversity | Reduction in caloric intake in both TRF groups vs. control | [204] |
| n = 8 prediabetic BMI 32.2 ± 4.4 kg/m2 | eTRF (6-h eating window and dinner before 3 pm) vs. 12-h eating period | Randomised crossover trial, 5 weeks’ intervention with a 7-week washout period | eTRF reduced insulin levels and improved insulin sensitivity, lowered blood pressure, reduction in oxidative stress and appetite in the evening. | Isocaloric | [181] |
| Breakfast vs. dinner calories | |||||
| n = 93 Overweight and obese women BMI 32.4 ± 1.8 kg/m2 | 1440 KCal consumed over breakfast/lunch/dinner 700, 500, 200 kcal vs. 200,500, 700 kcal | Randomized parallel-arm study for 12 weeks. | High caloric breakfast group showed greater weight loss and waist circumference, fasting glucose, insulin, triglycerides, HOMA-IR. Ghrelin, hunger vs satiety improved. | [205] | |
| n = 1245 non-obese, non-diabetic middle-aged adults | Daily caloric intake at dinner (<33% vs. 33–48 vs. ≥48% of daily kcal) | 6 years | Consuming more calories at dinner is associated with an increased risk of obesity, metabolic syndrome and NAFLD | [206] | |
TRF (time-restricted feeding), TRE (time-restricted eating), NAFLD (non-alcoholic fatty liver disease), HOMA-IR (homeostatic model assessment for insulin resistance), HbA1C (haemoglobin A1C), BDNF (brain-derived neurotrophic factor).