Can you fast while dieting?

Krista Varady
Photo: Roberta Dupuis-Devlin

Alternate-day fasting diets are just as effective as diets that restrict calories every day, researchers at the University of Illinois at Chicago report.

The study, published in JAMA Internal Medicine, followed 100 obese adults for a year. Participants were assigned to one of three diet groups: alternate-day fasting, everyday calorie restriction, and a control group.

Those in the alternate-day fasting group consumed only about 500 calories every other day. On the off-days, or “feast” days, participants ate whatever they wanted. The everyday restriction group reduced their daily calorie intake by about 25 percent, to about 1500 calories each day.

Results showed no significant difference in weight loss between alternate-day fasting  (6%) and everyday calorie restriction (5.3%). But both groups saw effective weight loss when compared to control.

Principal investigator Krista Varady says that the findings reinforce alternate-day fasting as a strategy for weight loss.

“Obesity is a complex disease with many causes and many serious consequences,” said Varady, an associate professor of nutrition in the UIC College of Applied Health Sciences. “The results of this study illustrate that alternate-day fasting is an effective option for achieving and sustaining weight loss, especially for men and women who have tried but failed to lose weight by daily calorie restriction.”

The new study is the largest and longest study of alternate-day fasting to date.

“When it comes to weight loss, people need to find what works for them,” said Varady, who is author of the book, “The Every Other Day Diet,” published by Hachette. “Alternate-day fasting is another tool in our arsenal.”

Co-authors on the paper are John Trepanowski, Cynthia Kroeger, Dr. Adrienne Barnosky, Monica Klempel, Surabhi Bhutani, Kristin Hoddy, Kelsey Gabel and Sally Freels of UIC; Joseph Rigdon of Stanford University; and Jennifer Rood and Eric Ravussin of the Pennington Biomedical Research Center.

The study was supported by grant RO1HL106228 from the National Institutes of Health/National Heart, Lung and Blood Institute, and grants P30DK072476 and F32DK107157 from the National Institute of Diabetes and Digestive and Kidney Diseases