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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 201364 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 2019137 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 201946 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 201659 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 201254 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 201532 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 201979 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 201016 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.
- Table 2.
Outcomes of risk factors for cardiovascular disease and type 2 diabetes in 26 individual studies of 22 intermittent fasting trials enrolling obese adults without type 2 diabetes
RISK FACTOR OUTCOME N STUDIES Blood pressure ↔ 324 Examined in 16 studies, with no change in 9 studies10,13,27,29,35,37,42,43,47 ↓ 226 Examined in 16 studies, with a decrease in 7 studies11,15,21,24,25,49,50 Body weight ↓ 764 Decrease seen in 22 studies10,11,13,15,19,20,22–25,27–29,33,35,37,41–43,49,47,50 BMI ↓ 566 Decrease seen in the 16 studies measuring BMI10,13,15,19,20,23–25,28,29,35,37,42,43,47,50 Diabetes • Glucose level ↔ 409 Examined in 17 studies, with no change in 11 studies10,19,24,25,27,32,35,38,40,42,43 ↓ 192 Examined in 17 studies, with a decrease in 5 studies13,15,20,23,41 ↑ 24 Examined in 17 studies, with an increase in 1 study11 • HbA1c level ↓ 54 Decrease seen in the 1 study measuring HbA1c level42 • Insulin level ↓ 407 Decrease in 8 studies, decreasing trend in 3 of 11 studies measuring insulin level11,13,15,19,20,25,27,32,35,41,43 BMI—body mass index, HbA1c—hemoglobin A1c.
- Table 3.
Outcomes of risk factors for cardiovascular disease and type 2 diabetes in 5 intermittent fasting studies enrolling obese adults with type 2 diabetes
RISK FACTOR OUTCOME N STUDIES Blood pressure NA NA Not studied in obese patients with type 2 diabetes Body weight ↓ 174 Decrease seen in all 5 studies12,16,17,21,34 BMI ↓ 174 Decrease seen in all 5 studies12,16,17,21,34 Diabetes • Glucose level ↓ 78 Decrease seen in the 3 studies measuring glucose level12,21,34 • HbA1c level ↓ 164 Decrease seen in the 4 studies measuring HbA1c level16,17,21,34 • Insulin level ↓ 27 Decrease seen in the 1 study measuring insulin level34 BMI—body mass index, HbA1c—hemoglobin A1c, NA—not available.
