Does Alternate-Day Fasting Improve Weight Loss?

Alternate-day fasting did not benefit weight loss efforts in obese adults, according to the results of a new study.

The randomized clinical trial included 100 obese adults from 18 to 64 years of age. Thirty-four participants were assigned to alternate-day fasting and consumed 25% of calories on fasting days and 125% of energy on non-fasting days, 35 participants were assigned to the calorie restriction group and consumed 75% of their daily energy needs, and 31 were assigned to the control group. The year-long trial was divided evenly into a weight loss phase and weight maintenance phase, and changes in body weight were assessed as the primary outcome. In addition, researchers measured cardiovascular disease risk indicators, and tracked adherence to the assigned dietary intervention with a 7-day food record survey administered every 3 months.
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At 6 and 12 months, the mean weight loss between participants in the alternate-day fasting group and participants in the calories restriction group were similar relative to participants in the control group.

Cardiovascular risk indicators, such as blood pressure, heart rate, triglycerides, fasting glucose, fasting insulin, and insulin resistance, did not differ at 6 or 12 months between the alternate-day fasting and calories restriction groups.

In addition, the mean high-density lipoprotein cholesterol levels in participants in the alternate fasting group significantly increased at 6 months compared with those in the calorie restriction group. At 12 months, the mean high-density lipoprotein did not significantly increase in participants in the alternate-day fasting group, but mean low-density lipoprotein cholesterol levels were significantly higher than those in the calories restriction group.

The dropout rate was highest in the alternate-day fasting group (38%) compared with the calorie restriction (19%) and control (26%) groups. Likewise, adherence in the alternate-day fasting group was low as participants consumed more calories on fast days and less calories on non-fast days than the prescribed amounts, while the participants in the calorie restriction group met their daily calorie intake.

“The alternate-day fasting diet was not superior to the daily calorie restriction diet with regard to adherence, weight loss, weight maintenance, or improvement in risk indicators for cardiovascular disease,” the researchers concluded.

“Taken together, these findings suggest that alternate-day fasting may be less sustainable in the long term, compared with daily calorie restriction, for most obese individuals.”

—Melissa Weiss

Reference:

Trepanowski JF, Kroeger CM, and Barnosky A. Effect of Alternate-Day Fasting on weight maintenance, and cardioprotection among metabolically healthy obese adults: a randomized clinical trial [pubslihed online May 1, 2017]. JAMA Intern Med. doi:10.1001/jamainternmed.2017.0936.