Overweight dieters who lose the pounds only to put them back on often attribute the rebound to their lack of willpower. But new research suggests that persistent changes in certain physiological factors can thwart a dieter’s best intentions. Research appearing in the October 27 issue of the New England Journal of Medicine finds that dieting causes long-term changes in the levels of several hormones that regulate body weight and increase appetite.
The research, by investigators from Melbourne, Australia, involved 50 overweight or obese patients (34 of whom completed the study) who participated in a 10-week weight loss program that involved following a very low-calorie diet of 550 calories per day for 8 weeks that resulted in an average weight loss of about 30 pounds. During weeks 9 and 10, enrollees who had lost 10% or more of their starting body weight then were transitioned to a maintenance diet and followed up for another 52 weeks. Levels of various hormones that are known to play a role in regulating hunger and weight (leptin, peptide YY, cholecystokinin, insulin, ghrelin, and gastric inhibitory polypeptide) were also measured at the start of the trial, at the beginning of the maintenance diet, and after 52 weeks on the maintenance diet. Study participants also reported their feelings of hunger and desire to eat during these measurement sessions.
Both appetite and appetite-regulating hormone levels remained significantly different from baseline levels a full year after the calorie-restricted diets had ended, the researchers found. Such differences would be expected to facilitate regain of lost weight, the investigators wrote.
“Taken together, these findings indicate that in obese persons who have lost weight, multiple compensatory mechanisms encouraging weight gain, which persist for at least 1 year, must be overcome in order to maintain weight loss,” the investigators wrote. “These mechanisms would be advantageous for a lean person in an environment where food was scarce, but in an environment in which energy-dense food is abundant and physical activity is largely unnecessary, the high rate of relapse after weight loss is not surprising.”