Alternate –Day Fasting: Any better than other Diets?

Posted by Dr. Daniela Lamers on Sep 12, 2017 4:33:00 PM

Is alternate-day fasting regimes the new trend?

Alternate-day fasting regimens have gained particular popularity in the last decade. The strategy of alternate-day fasting is to implement a fasting day, where individuals consume only 25% of their calories (approximately 500 kcal). The fasting day alternates with a “feast” day (every other day) where foods and liquids can be consumed ad libitum.

The idea behind is to eat the way our ancestors did – who had a life expectancy of 35 years without obesity and heart attacks – and the hope to lose weight with a diet which is said to be easier to stick to than traditional, everyday calorie restriction diets.

In the literature some short term studies1-5 reported the success of alternate fasting with regard to body weight loss (3%-7% after 2-3 month) and to improvements of lipid profiles, blood pressure and insulin sensitivity, BUT no long term randomised clinical trial has ever evaluated its efficacy and compared the approach to “conventional” diets.


Alternate-day fasting diet x calorie restriction diet

In light of that, John Trepanowski and colleagues6 from the University of Illinois at Chicago recently conducted a clinical trial in which they included 100 obese adults (86% women) and randomly assigned them to 1 of 3 groups over 1 year: alternate-day fasting (25% of energy needs on fast days and 125% energy needs on feast days), calorie restriction (75% energy needs over the day), or a control group who did not change the diet. The trial consisted of a 6 month intervention period followed by a 6 month maintenance phase.

The results show that the mean body weight loss in the fasting group and the calorie-restriction group was similar at month 6 (both groups –6.8 %, compared to the group without diet change). By the end of the study (at month 12) weight loss was –6.0 % vs. –5.3 % for the fasting and calorie-restriction diet, respectively.

Notably, participants in the alternate-day fasting group ate more on the fast days and less on the feast days, revealing that participants had problems to stick to the fasting diet, whereas participants in the calorie- restriction group basically adhered to their regimen. This finding argues against a higher adherence to alternate day fasting compared to other diet forms.

This is also reflected by the higher drop-out rate in the alternate-day fasting group compared to the calorie-restriction and control group (38% vs. 29% vs. 26%, respectively), which to some extend limit the interpretation of the results and underlines that alternate-day fasting is not as easy as expected.

Up to now, strategies for losing weight appear endless. They seem to emerge “every other day”. And of course every author rates his diet as the most successful.  In the end, which diet to be used to reduce weight and (equally important) keep it off in the long term, has to be decided on an individual basis – choose the one that is most suitable for you, you can live happily with and you can adhere to.


  1. Bhutani S, Klempel MC, Kroeger CM, Trepanowski JF, Varady KA. Alternate day fasting and endurance exercise combine to reduce body weight and favorably alter plasma lipids in obese humans. Obesity (Silver Spring) 2013; 21(7): 1370-9.
  1. Hoddy KK, Kroeger CM, Trepanowski JF, Barnosky A, Bhutani S, Varady KA. Meal timing during alternate day fasting: Impact on body weight and cardiovascular disease risk in obese adults. Obesity (Silver Spring) 2014; 22(12): 2524-31.
  1. Klempel MC, Kroeger CM, Varady KA. Alternate day fasting (ADF) with a high-fat diet produces similar weight loss and cardio-protection as ADF with a low-fat diet. Metabolism 2013; 62(1): 137-43.
  1. Varady KA, Bhutani S, Church EC, Klempel MC. Short-term modified alternate-day fasting: a novel dietary strategy for weight loss and cardioprotection in obese adults. Am J Clin Nutr 2009; 90(5): 1138-43.
  1. Catenacci VA, Pan Z, Ostendorf D, Brannon S, Gozansky WS, Mattson MP, Martin B, MacLean PS, Melanson EL, Troy Donahoo W. A randomized pilot study comparing zero-calorie alternate-day fasting to daily caloric restriction in adults with obesity. Obesity (Silver Spring) 2016; 24(9): 1874-83.
  1. Trepanowski JF, Kroeger CM, Barnosky A, Klempel MC, Bhutani S, Hoddy KK, Gabel K, Freels S, Rigdon J, Rood J, Ravussin E, Varady KA. Effect of Alternate-Day Fasting on Weight Loss, Weight Maintenance, and Cardioprotection Among Metabolically Healthy Obese Adults: A Randomized Clinical Trial. JAMA Intern Med 2017; 177(7): 930-938.


Topics: Clinical trials in Obesity