Alternate-day Fasting and Disordered Eating Symptoms

Alternate-day fasting, or ADF, is a newer weight-loss approach where individuals eat freely one day (“feed day”), and then restrict their food intake by 25% the next day (“fast day”). Researchers at the University of Chicago wondered if this approach to switching intake day by day might foster disordered eating patterns, and designed a study to evaluate adverse effects and eating disorder symptoms during ADF (Nutrition Journal 2015; 14:44).

During an 8-week trial, Drs. Kristin K. Hoddy and colleagues studied 74 subjects who were recruited through advertisements in the Chicago area. Their subjects ranged from 25 to 65 years of age and had body mass indexes between 30 and 39 kg/m²; they had no history of cardiac disease or diabetes and all were non-smokers.

All the subjects consumed 25% of their baseline energy on the fast day, which lasted 24 hours, and ate freely on each alternating feed day. All meals were consumed outside the research center. All subjects also filled out an adverse event questionnaire at two points–before the trial began and after the study ended. Disordered eating symptoms were measured with the Multidimensional Assessment of Eating-Disorder Symptoms (MAEDS). The MAEDS measures 6 areas related to eating disorders, including binge eating, restrictive eating, purging behavior, fear of fatness, avoiding “forbidden” foods, and depression. The researchers also administered the Body Shape Questionnaire.

Dropouts, weight loss, and adverse events

Fifty-nine subjects completed the trial. Those who dropped out of the study did so for a number of reasons, including inability to comply with the diet and scheduling conflicts. At the end of the 8 weeks, the group’s mean body weight loss was about 4%. The most common side effect was bad breath (29%), followed by constipation and dizziness (each affected 17% of participants at the end of treatment).

At the end of the study, the authors noted that depression and binge-eating symptoms had decreased, while purging behaviors and fear of fatness remained unchanged; however, body image as measured by the BSQ improved. The ADF program helped subjects increase restrictive eating, suggesting the program might help control unrestrained eating behaviors and improve body image perception.

There were several limitations to the study. For example, the authors felt the adverse events questionnaire could have been more comprehensive. They noted that the questionnaire omitted questions about cold intolerance, hair loss, headaches, muscle cramps, and difficulty concentrating. A longer-term study and one that compared ADF with caloric restriction might also provide more helpful information, according to the authors.

[Comment: The results are perhaps surprising, particularly to those of us working in the eating disorders field, who routinely encounter such extreme dieting behaviors as precursors to full eating disorders. A critical caveat is that the study reported on the 59 who completed the study, and the 15 others dropped out for various reasons. Those who dropped out might have developed more disordered eating. Also, the period of study was short (only 8 weeks). For these reasons, decisions about the safety of such dietary practices should be made with considerable caution.]