Is Alternate-Day Fasting Better for Weight Loss?

There has been a lack of long-term randomized clinical studies on the efficacy of alternate-day fasting
There has been a lack of long-term randomized clinical studies on the efficacy of alternate-day fasting

Compared to daily calorie restriction, alternate-day fasting does not lead to better adherence, weight loss/maintenance, or cardioprotection, according to a study published in JAMA Internal Medicine.

There has been a lack of long-term randomized clinical studies on the efficacy of alternate-day fasting. To evaluate the effects of alternate-day fasting vs. daily calorie restriction on weight loss and maintenance, and risk factors for cardiovascular disease, researchers from the University of Illinois at Chicago performed a single-center randomized trial which included 100 metabolically healthy obese patients. 

Study participants were randomized to one of the following groups for 12 months (6 months weight-loss + 6 months weight-maintenance phases):

  • Alternate-day fasting: 25% of energy needs on fast days; 125% of energy needs on alternating "feast days"
  • Calorie restriction: 75% of energy needs daily
  • No intervention: control

The study's primary outcome was change in body weight; secondary outcomes included adherence to the intervention arm and risk factors for cardiovascular disease. 

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More participants dropped out of the alternate-day fasting group vs. the daily calorie restriction group and control group (38% vs. 29% vs. 26%, respectively). At Month 6, the average weight loss was similar for patients in the alternate-day fasting group and the daily calorie restriction group (–6.8% [95% CI: –9.1 to –4.5] vs. –6.8% [95% CI: –9.1 to –4.6]). At Month 12, the average weight loss was also similar for both intervention groups (–6.0% [95 %CI: –8.5 to –3.6] vs. –5.3% [95% CI: –7.6 to –3.0]).

The study authors observed that participants in the daily calorie restriction group achieved their prescribed energy goals whereas participants in the alternate-day fasting group ate more than prescribed on their "fast"days and ate less than prescribed on their "feast" days. 

At Months 6 and 12, there were no significant differences in blood pressure, heart rate, triglycerides, fasting glucose, fasting insulin, insulin resistance, C-reactive protein, or homocysteine concentrations between the intervention groups. 

Mean HDL levels at Month 6, however, were significantly higher among those in the alternate-day fasting group (6.2mg/dL [95% CI: 0.1–12.4]) but not at Month 12 (1.0mg/dL [95% CI: –5.9 to 7.8]) vs. the daily calorie restriction group. By Month 12, mean LDL levels were significantly higher among those in the alternate-day fasting group (11.5mg/dL [95% CI: 1.9–21.1]) vs. the daily calorie restriction group. 

For more information visit jamanetwork.com.