Clinical Edge

Summaries of Must-Read Clinical Literature, Guidelines, and FDA Actions

Efficacy of Alternate-Day Fasting on Weight Loss

JAMA Intern; ePub 2017 May 1; Trepanowski, et al

Among metabolically healthy obese adults, alternate-day fasting did not produce superior adherence, weight loss, weight maintenance, or cardioprotection vs daily calorie restriction, a recent study found. The single-center randomized clinical trial from October 1, 2011, to January 15, 2015, included 100 obese adults aged 18 to 64 years (mean BMI, 34) randomized to 1 of 3 groups for 1 year: alternate-day fasting, calorie restriction, or a no-intervention control. The trial involved a 6-month weight-loss phase followed by a 6-month weight maintenance phase. Researchers found:

  • Mean weight loss was similar for participants in the alternate-day fasting and those in the daily calorie restriction group at month 6 and month 12 relative to the control group.
  • 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.


Trepanowski JF, Kroeger CM, Barnosky A, et al. Effect of alternate-day fasting on weight loss, weight maintenance, and cardioprotection among metabolically healthy obese adults. A randomized clinical trial. [Published online ahead of print May 01, 2017]. JAMA Intern Med. doi:10.1001/jamainternmed.2017.0936.


Alternate-day fasting is a diet plan that has become very popular, with some popular diet books now suggesting this approach for weight loss.1 In general, alternate-day fasting involves eating very little, perhaps about 500 calories on fast days, and eating a regular diet on non-fast days. Animal studies have shown that intermittent dietary restriction can improve blood pressure, glucose metabolism, and vulnerability of cardiac and brain cells to injury. In humans, some short-term studies have shown slight to moderately more weight loss and decreased fat mass using intermittent fasting compared to an isocaloric diet without intermittent fasting.2 This 1-year long, randomized clinical trial comparing the effects of alternate-day fasting vs daily calorie restriction on body weight and risk factors showed no benefit to alternate-day fasting on either weight loss or other cardiometabolic parameters. —Neil Skolnik, MD

  1. Mosley M, Spencer M. The Fast Diet. New York, NY: Atria Books; 2012.
  2. Stote K, Baer DJ, Spears K, et al. A controlled trial of reduced meal frequency without caloric restriction in healthy, normal-weight, middle-aged adults. Am J Clin Nutr. 2007;85:981–988.