Table 1.
Summary of IF studies: Total IF participants = 944.
| STUDY, Y | N | POPULATION* | LEVEL OF EVIDENCE | DURATION | WEIGHT LOSS, % OF BASELINE WEIGHT | INTERVENTION† | KEY RESULT |
|---|---|---|---|---|---|---|---|
| Anton et al,10 2019 | 10 | Obese, > 65 y | II | 4 wk | 2.2 | 16-h daily fast; self-reported | IF is feasible in older adults and leads to weight loss |
| Antoni et al,11 2018 | 41 | Overweight and obese | I | Until 5% weight loss is reached | 5.3 | 2-d fast (25% of caloric needs) and 5-d ad libitum calorie intake vs CR; self-reported | 59 d to achieve 5% weight loss with IF; not statistically different in CR group (73 d) |
| Arnason et al,12 2017 | 10 | Obese, T2D | II | 2 wk | 1.4 | 18- to 20-h daily fast as a goal, but average fast was 16.8 h; 2-wk follow-up; self-reported | Short-term IF might be safe in patients with T2D and might improve glycemic control |
| Bhutani et al,13 2013 Bhutani et al,14 2013 |
64 | Obese | I | 12 wk | 3.2 | Alternated 25% of caloric needs with ad libitum calorie intake vs usual diet with or without exercise; self-reported | IF in combination with exercise is more effective than either method alone |
| Bowen et al,15 2018 | 136 | Overweight and obese | I | 16 wk | 10.6 | 3-d fast, 3-d CR, and 1-d ad libitum intake vs CR; 8-wk maintenance; self-reported | CR combined with IF does not improve on weight loss of CR alone |
| Carter et al,16 2016 | 51 | Obese, T2D | I | 12 wk | 5.9 | 2-d fast (1670 to 2500 kJ/d) and 5-d usual diet vs CR; self-reported | IF is a viable alternative to CR for weight loss and glycemic control in T2D |
| Carter et al,17 2018 Carter et al,18 2019 |
137 | Obese, T2D | I | 52 wk | 6.8 | 2-d fast (25% of usual calorie intake) and 5-d usual diet vs CR; 1-y follow-up; self-reported | Similar decrease in HbA1c level and weight with IF or CR; weight is stable and HbA1c level climbs in follow-up |
| Catenacci et al,19 2016 | 26 | Obese | I | 8 wk | 8.7 | Alternated 0% usual calorie intake with ad libitum intake vs CR; 24-wk follow-up; monitored | IF is a safe weight-loss strategy; no increase in risk of weight regain |
| Cho et al,20 2019 | 31 | Overweight and obese | I | 8 wk | 5.0 | Alternated 25% usual calorie intake with ad libitum intake vs usual diet with or without exercise; self-reported | Exercise does not improve weight loss for IF alone |
| Corley et al,21 2018 | 41 | Obese, T2D | II | 12 wk | 0.8 | 2-d fast (2 small snacks, 1 light meal) and 5-d ad libitum intake; self-reported | IF safe in T2D; promotes weight loss and glycemic control |
| Coutinho et al,22 2018 | 35 | Obese | I | 12 wk | 13.0 | 3-d fast (25% of caloric needs) and 4-d full caloric needs vs CR; self-reported | Similar weight losses result from IF and CR |
| Eshghinia and Gapparov,23 2011 | 26 | Obese women | II | 4 wk | 4.9 | 3-d fast (25% to 40% of usual caloric intake) and 4-d CR (10% decrease in usual caloric intake) per wk; self-reported | Short-term IF with CR is a viable weight-loss strategy in obesity |
| Eshghinia and Mohammadzadeh,24 2013 | 15 | Obese women | II | 6 wk | 7.1 | 3-d fast (25% to 30% of caloric needs), 3-d usual diet, and 1-d ad libitum intake; self-reported | Short-term IF is a viable weight loss strategy in obesity |
| Gabel et al,25 2018 Gabel et al,26 2019 |
46 | Obese | I | 12 wk | 3.2 | 16-h fast daily vs usual-diet historical controls; self-reported | IF leads to weight loss compared with baseline and control group |
| Harvie et al,27 2011 | 107 | Obese women | I | 24 wk | 7.9 | 2-d fast (very low-calorie intake) and 5-d usual diet vs CR; self-reported | IF is as effective as CR for weight loss and insulin sensitivity |
| Headland et al,28 2019 | 244 | Obese | I | 52 wk | 5.6 | 2-d fast (25% of usual calorie intake) and 5-d usual diet vs CR; self-reported | IF and CR have similar weight loss results at 1 y |
| Hoddy et al,29 2014 Hoddy et al,30 2015 Hoddy et al,31 2016 Hoddy et al,32 2016 |
59 | Obese | I | 8 wk | 4.2 | Alternated daily 25% of baseline caloric needs with ad libitum caloric intake; self-reported | IF is a safe weight-loss strategy; no increased risk of disordered eating; might decrease insulin resistance |
| Hutchison et al,33 2019 | 88 | Overweight and obese women | I | 8 wk | 4.6 | 3-d fast (32%–37% of energy requirements) and 4 d at 100% or 145% of energy requirements vs CR and control group; self-reported | Combining CR and IF is more effective for weight loss than either alone |
| Kahleova et al,34 2014 | 54 | Obese, T2D | I | 12 wk | 3.9 | 16-h daily fast vs CR; self-reported | IF is more effective than CR for weight loss and glycemic control in T2D |
| Klempel et al,35 2012 Kroeger et al,36 2012 |
54 | Obese women | II | 8 wk | 3.4 | 1-d fast (very low-calorie intake) and 6-d CR; self-reported | IF combined with CR promotes weight loss in obese women |
| Klempel et al,37 2013 Klempel et al,38 2013 Klempel et al,39 2013 Varady et al,40 2015 |
32 | Obese women | II | 8 wk | 4.5 | Alternated 25% of usual calorie intake with 125% of usual calorie intake; high-fat vs low-fat diet; self-reported | IF is effective for weight loss with a high-fat or low-fat diet composition |
| Schübel et al,41 2018 | 150 | Obese | I | 12 wk | 6.4 | 2-d fast (25% of calorie requirements) and 5-d usual diet vs CR and control group; 12-wk maintenance; 26-wk follow-up; self-reported | Weight loss and maintenance is similar in IF and CR |
| Sundfør et al,42 2018 | 112 | Obese | I | 26 wk | 8.4 | 2-d fast (20% of calorie requirements) and 5-d usual diet vs CR; 26-wk maintenance; self-reported | Weight loss and maintenance are similar in IF and CR |
| Trepanowski et al,43 2017 Trepanowski et al,44 2018 Kroeger et al,45 2018 Kalam et al,46 2019 |
79 | Obese | I | 24 wk | 6.0 | Alternated 25% of usual calorie intake with 125% of usual calorie intake vs CR and control group; 24-wk follow-up; self-reported | IF promotes weight loss and weight maintenance similar to CR |
| Varady et al,47 2009 Bhutani et al,48 2010 |
16 | Obese | II | 8 wk | 5.8 | Alternated 25% of energy needs with ad libitum caloric intake; self-reported | IF is a viable option for weight loss in obese individuals |
| Varady et al,49 2013 | 30 | Obese | I | 12 wk | 6.5 | Alternated 25% of baseline energy needs with ad libitum caloric intake vs usual diet; monitored | IF is effective for weight loss in obese individuals |
| Zuo et al,50 2016 | 40 | Obese | II | 12 wk | 10.0 | 1-d fast (430 kcal) and 6-d high-protein diet; 52-wk follow-up; monitored | IF with a high-protein diet is effective for weight loss, with low risk of weight regain |
CR—calorie restriction, HbA1c—hemoglobin A1c, IF—intermittent fasting, T2D—type 2 diabetes.
*
Where sex is not specified, both men and women were enrolled.
†
Self-reported indicates participants reported consumption in food diaries; monitored indicates investigators monitored participants’ consumption.