What Matters

Intermittent energy restriction


My patients find it extremely difficult to determine the number of calories they consume on a daily basis. This activity can be laborious and time consuming, even when you have the right “app.”

So, when I tell my overweight and obese patients to restrict their caloric consumption to lose weight, the discussion usually begins with, “I know this might be difficult, but …” And it usually ends with me feeling a little less than anemic optimism.

Dr. Jon O. Ebbert

Dr. Jon O. Ebbert

This is why the idea of intermittent energy restriction (IER) seems so appealing. IER is defined by periods of fasting alternating with periods of no or minimal dietary intervention. In other words, no calorie counting during the nonfasting times.

But is it effective for weight loss?

C.S. Davis of Monash University, Melbourne, and colleagues conducted a systematic review of IER for weight loss (Eur J Clin Nutr. 2016 Mar;70[3]:292-9). The authors searched for articles evaluating the IER for weight loss among overweight and obese adults aged 18 years or older. IER was defined as periods of low energy intake (fast) alternating with periods of normal food intake (feed).

Eight studies were included in this review. Included studies defined low energy intake as 25%-50% of daily energy, or 400-1,400 kcal/day. The feed period was defined as either eating ad libitum or no less than 1,400 kcal/day. Studies varied in their approach and ranged from 2-4 consecutive fast days per week, followed by consecutive feed days, to three cycles of 5 weeks of fasting, followed by 5 weeks of ad lib eating.

IER was associated with 0.2-0.8 kg of weight loss per week. IER was associated with weight loss comparable to daily energy restriction (DER; that is, a typical diet). IER was comparable to typical daily energy restriction diets for fat mass, free-fat mass, and waist circumference.

The authors state that the amount of weight loss achieved with IER for a 100-kg individual would be associated with a 5% reduction in weight over a 5-week to 6-month time period. A 5% reduction is associated with a clinically significant reduction in health risk.

However, the authors found that fewer study participants planned to stick with IER beyond 6 months, compared with DER. Perhaps despite the difficulty that may exist in counting calories every day, the habit of doing the counting every day may be easier than doing it on an intermittent basis.

Regardless, IER is an option that may be beneficial to some patients. If other things haven’t worked for your patients, it is definitely worth a try.

Dr. Ebbert is professor of medicine, a general internist at the Mayo Clinic in Rochester, Minn., and a diplomate of the American Board of Addiction Medicine. The opinions expressed are those of the author and do not necessarily represent the views and opinions of the Mayo Clinic. The opinions expressed in this article should not be used to diagnose or treat any medical condition, nor should they be used as a substitute for medical advice from a qualified, board-certified practicing clinician. Dr. Ebbert has no relevant financial disclosures about this article.

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