Short-Term Overeating Could Make Long-Term Weight Loss Tougher

If you think a few weeks of slothful behavior and caloric overindulgence can be easily worked off at the gym, think again. New Swedish research suggests that just a month's worth of unhealthy living changes physiology, making piled-on fat even harder to lose. "A short period of [over-eating] can have later long-term effects," said study co-author Dr. Torbjorn Lindstrom, an associate professor in the department of medical and health sciences within the faculty of health sciences at Linkoping University. "Based on this, it can be recommended to avoid very high food-intake that might occur during shorter periods in normal life."

Lindstrom and his colleagues report their findings in the current issue of Nutrition & Metabolism. They focused on 18 normal-weight healthy participants, averaging 26 years of age. For one month, all 18 were placed on a restricted physical activity regimen that involved the equivalent of no more than 5,000 steps per day. Five thousand steps, the team noted, is the threshold for a "sedentary" lifestyle, whereas a "physically active" lifestyle involved 10,000 steps or more. In addition, participants embarked on diets involving a 70 percent jump in daily caloric intake mainly from fast food amounting to about 5,750 calories ingested per day. The research also included a comparison group who did not change their diet/activity.

By the end of the month, the feasting group gained an average of 14 pounds. Their fat mass, specifically, was found to have gone up from about 20 percent of total body weight, to nearly 24 percent after the month-long intervention. Participants lost most of that new weight over the ensuing six months. However, one year after the study's end, participants still registered a noticeable gain in fat mass compared with their pre-study status. This fat stuck around despite the fact that the participants had returned to their lower-calorie pre-study diet and more active routines. Two-and-a-half years after the study, fat mass gains were even greater, registering just under 7 pounds on average, the researchers found. There was no such long-term change among the control group who had stuck to their usual diet.