Johns Hopkins Health Alerts | Nutrition and Weight Control | Overeating and Weight Gain

If you overate for a week or so and gained weight, would you automatically eat less than usual to lose those extra pounds? According to the results of a recent study, the answer may be “no.”

Eating more calories than you expend is an important cause of obesity. In fact, regardless of your genetic predisposition to obesity or your resting metabolic rate, you cannot gain weight without consuming more calories than you burn. Even small excesses in calorie intake can add pounds over the long term. For example, a person who overeats by just 25 calories a day will consume 9,125 excess calories over the course of a year and gain 2.5 lbs. (a pound of body fat is equivalent to 3,500 calories). A woman weighing 125 lbs. who starts this pattern at age 20 would weigh 175 lbs. by the time she is 40.

To point to overeating as the cause of obesity is overly simplistic, however. It does not explain why a 125-lb. woman can eat 1,800 calories a day and not gain weight, while another 125-lb. woman struggles to avoid gaining weight on 1,200 calories a day. This difference occurs because numerous other factors contribute to weight gain, including resting metabolic rate and physical activity. Nevertheless, obese people must be consuming more calories than required by their individual make-ups and activity levels; otherwise they would not store excess body fat. Thus, if you’re overweight, you must reduce your calorie intake to lose weight.

Overeating is the subject of an interesting study reported in the journal, Physiology and Behavior (Volume 84, page 669).

Researchers prepared meals for 12 normal-weight people for seven weeks. During the first two weeks, the participants were allowed to eat as much or as little as they wanted. For the next two weeks, they were purposely fed 35% more calories than they ate during the first two weeks, which resulted in a weight gain of about five lbs.

Next, they were told to return to eating as much or as little as they wanted for three weeks. Surprisingly, although the subjects had complained of “feeling stuffed” during the overfeeding period, they didn’t eat any fewer calories during the last three weeks than they did during the first two weeks of the study. Even so, they lost about half of the weight they had gained, most likely because their metabolic rate rose in response to the weight gain.

The researchers write that the absence of calorie cutting after overfeeding might have been related to eating in the same environment and being offered the same portion sizes as in the first two weeks of the study. Whatever the reason, this study points out that you cannot rely on being able to eat less after a period of overeating, and we recommend that you avoid overeating in the first place.

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Johns Hopkins Health Alerts | Nutrition and Weight Control | Overeating and Weight Gain