Therapy for obese patients begins with weight loss by daily calorie restriction. Many patients, however, find daily food restriction difficult. Intermittent fasting, where a patient cycles between eating either no food/significantly fewer calories and unrestricted eating, is an alternative to traditional diets.
Alternate-day fasting is one method of intermittent fasting. On this “every-other-day” diet, patients alternate between eating fewer calories and eating without restriction. Despite its popularity, as of 2017, there were no long term randomized clinical trials evaluating its efficacy.
Researchers conducted a randomized controlled trial comparing alternate-day fasting to a traditional diet. Both diets were compared to a control group. The study assigned 100 obese adults, with no history of cardiovascular disease or diabetes, to 1 of these three groups.
During the first 6 months of the trial, patients randomized to alternate-day fasting ate 25% of their usual calories on fast days (all during lunch) and 125% on “feast” days, while patients randomized to daily calorie-restriction ate 75% of their usual calories every day. The third “control” group did not change their diet. Patients assigned to either alternate-day fasting or the traditional diet were given their meals for the first 3 months. For the remaining 3 months, patients met with a dietician weekly.
During the last 6 months of the trial, the emphasis shifted from weight-loss to weight-maintenance with calorie levels increasing by 25% for both the alternate-day fasting and daily calorie restriction groups.
At six months, both the alternate-day fasting and daily calorie control groups lost weight. However, neither diet was superior – both lost 6.8% compared to the control group. At 12 months, weight loss was again similar, with the alternate-day fasting group losing 6% versus 5.3% in the daily calorie control group (not significantly different). Likewise, there was no significant difference between the intervention groups in terms of weight regained or body composition (e.g. % fat lost).
The study also looked at blood pressure, heart rate, fasting glucose, fasting insulin, total cholesterol and triglycerides. For the most part, the researchers found no difference, although the alternate-day fasting group had significantly higher LDL cholesterol (“bad cholesterol”) levels compared to the daily calorie control group at month 12.
The authors noted a higher drop-out rate in the alternate-day fasting group compared to the daily calorie restriction group (38% vs. 29%). They suggested that
…alternate-day fasting may be less sustainable in the long term, compared with daily calorie restriction…
However, they noted that depending on a person’s behavioral traits, some individuals who are trying to lose weight may prefer an intermittent type of diet as compared to a traditional diet and that…
It will be of interest to examine what behavioral traits (eg, ability to go for long periods without eating) make alternate-day fasting more tolerable for some individuals than others.
Trepanowski, J. F., Kroeger, C. M., Barnosky, A., Klempel, M. C., Bhutani, S., Hoddy, K. K., … & Ravussin, E. (2017). Effect of alternate-day fasting on weight loss, weight maintenance, and cardioprotection among metabolically healthy obese adults: a randomized clinical trial. JAMA internal medicine, 177(7), 930-938.
Photo by Jennifer Burk on Unsplash.
