Alternate-Day Fasting Cuts Insulin Resistance in Half: Study

Alternate-day fasting, or fasting every other day, lowered fasting insulin and insulin resistance more than calorie restriction in adults with overweight or obesity and insulin resistance, according to a new study in the journal Obesity.


For 12 months, the researchers worked with 43 people with a body-mass index (a measure of weight relative to height) of at least 25 kg/m and insulin resistance. Eleven of the participants were assigned to practice alternate-day fasting, 17 were assigned to daily calorie restriction, and the remaining 15 maintained their typical eating routine.

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Alternate-day fasters were instructed to eating 125% of their required calories one day and then drop to 25% of their required calories the next, continuing for the first six months, after which the balance switched to 150% and 100%. Those on calorie restriction were instructed to limit their calorie intake to 75% of their energy needs for the first six months and then 100% in the final six months.

After 12 months, those who followed the alternate-day fasting pattern reduced their weight by 8% compared to those following their typical eating routine, while those on the calorie-restricted diet reduced their body weight by 6% compared to the routine eaters. However, among the alternate-day fasters, the was a 52% reduction in fasting insulin and a 53% reduction in insulin resistance compared to 14% and 17% reductions, respectively, in those on the calorie-restricted diet.

“Taken together, these findings suggest that fasting generally produces superior reductions in insulin resistance compared with daily [calorie restriction] despite similar weight loss,” the researchers wrote. “Moreover, it is likely that these effects may be more pronounced in participants who display higher levels of insulin resistance at baseline,” said researcher Krista A. Varady, PhD, and colleagues. “These preliminary findings show that intermittent fasting may be more effective than daily [calorie restriction] to lower insulin resistance in adults at risk for developing diabetes.”

The researchers noted that those assigned to alternate-day fasting did not strictly stick to the program, eating more than recommended on fast days and less than recommended on feast days. “it is interesting that [alternate-day fasting] participants consumed almost twice as many calories on fast days but still observed greater metabolic effects compared with [calorie restriction] participants. This suggests that simply reducing energy intake by [approximately] 1,000 kcal/d a few days per week may have significant metabolic benefits.”

Want to learn more about insulin resistance? Read “Insulin Resistance: What You Need to Know.”

Diane Fennell

Diane Fennell

Senior Digital Editor for, Fennell has 16 years’ experience specializing in diabetes and related health conditions. Based in New York City, she has a degree from Columbia University.

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