Effect of Alternate-Day Fasting on Weight Loss

Study Questions:

Are the effects of alternate-day fasting compared with daily calorie restriction similar for weight loss, weight maintenance, and modification of cardiovascular (CV) risk factors?

Methods:

This was a single-center randomized clinical trial, which included obese adults (age 18-64 years of age) conducted between October 1, 2011 and January 15, 2015. Subjects were randomized to one of three groups (alternating fast and feast days; daily calorie restriction; or no-intervention). The alternating group consumed 25% of energy needs on fast days and 125% of energy needs on feast days. The daily calorie restriction group consumed 75% of energy needs every day. The trial involved a 6-month weight-loss phase followed by a 6-month weight maintenance phase. The primary outcome of interest was change in bodyweight. Secondary outcomes included adherence to the dietary intervention and risk indicators for CV disease.

Results:

A total of 100 participants (86 women and 14 men) were included. Mean age was 44 years. Drop out rates were highest in the alternate-day fasting groups (13 of 34 [38%]), compared with the daily calorie restriction groups (10 of 35 [29%]) or the control group (8 of 31 [26%]). Mean weight loss was similar for participants in the alternate-day fasting group and those in the daily calorie restriction group at the initial 6-month weight loss phase in the alternate fasting group (–6.8% [95% CI, –9.1% to –4.5%]) and in the daily calorie restriction group (–6.8% [95% CI, –9.1% to –4.6%]) as compared with the control group. Results were also similar between the two groups at 12 months. Participants in the alternate-day fasting group ate more than prescribed on fast days, and less than prescribed on feast days, while those in the daily calorie restriction group generally met their prescribed energy goals. There were no significant differences between the intervention groups in blood pressure, heart rate, triglycerides, fasting glucose, fasting insulin, insulin resistance, C-reactive protein, or homocysteine concentrations at month 6 or 12. Mean high-density lipoprotein cholesterol levels at month 6 significantly increased among the participants in the alternate-day fasting group, but not at month 12, relative to those in the daily calorie restriction group. Mean low-density lipoprotein cholesterol levels were significantly elevated by month 12 among the participants in the alternate-day fasting group compared with those in the daily calorie restriction group.

Conclusions:

The authors concluded that alternate-day fasting did not produce superior adherence, weight loss, weight maintenance, or cardioprotection as compared with daily calorie restriction.

Perspective:

These data suggest that alternating fasting with feasting is not beneficial for weight loss or maintenance of weight loss, and may be associated with adverse lipids as compared with daily calorie restriction.

Clinical Topics: Diabetes and Cardiometabolic Disease, Dyslipidemia, Prevention, Lipid Metabolism, Nonstatins, Diet

Keywords: Blood Pressure, Blood Pressure Determination, C-Reactive Protein, Caloric Restriction, Cholesterol, Glucose, Homocysteine, Insulin, Insulin Resistance, Lipids, Lipoproteins, HDL, Lipoproteins, LDL, Obesity, Primary Prevention, Risk Factors, Triglycerides, Weight Loss


< Back to Listings