The Centers for Disease Control and Prevention recommends that adults get two and a half hours of moderately intensive aerobic activity, such as brisk walking, each week, along with muscle-strengthening exercise, such as lifting weights, two days a week, in order to stay healthy. Exercise works your heart, lungs and muscles and helps prevent disease and obesity. But scientists have wondered if all this exercise does anything to change people’s eating habits, and a number of studies have been conducted to look at the eating habits of people who exercise.
Exercise and Appetite
Exercise burns energy, or calories. You lose weight when you expend more calories than you take in. If exercise is burning more calories, it seems logical that your body would want to take in more calories to make up the deficit. You’d be hungrier and eat more, so you’d end up not losing weight from exercising. But a 1998 report from psychologists at the University of Leeds found that, for most people, this isn’t true. Doctors looked at groups of both normal weight and obese people and found that even substantial exercise didn’t lead people to eat more.
Effects of Reducing Exercise
In 2003, the University of Leeds psychologists re-visited the idea of exercise and appetite. They found that exercise didn’t increase appetite in most people either over the short term of one to two days, or over longer periods of seven to 16 days. They also looked at people who had been very physically active who were forced into a more sedentary lifestyle. For these people, reducing their activity level didn’t reduce their appetite or change their eating habits. They ate just as much as they had when they were physically active, and therefore, gained weight. For some people, at least, the amount they eat is dictated more by habit than by appetite.
Compensators and Non-Compensators
When the University of Leeds psychologists looked at increases in exercise over 16 days, they found that some people, whom they labeled compensators, did begin to increase their food intake. But even this extra food intake only made up about 30 percent of the energy deficit realized from the increased exercise. Other people, the non-compensators, never changed their eating habits at all.
Exercise and Weight Control
The University of Leeds psychologists found that some people rewarded themselves with food when they exercised. They also overestimated the number of calories they burned through exercise, thus discounting the effect their rewards would have on their weight loss attempts. The psychologists found that the most effective weight loss programs combined exercise with a controlled eating program. Even then, the weight loss from exercise is not always as great as expected, since exercise increases muscle and may re-shape your body; you can be a size smaller without the scale budging much.
References
- Centers for Disease Control and Prevention: How Much Physical Activity Do Adults Need?
- International Journal of Obesity and Related Metabolic Disorders: Effects Of Exercise On Appetite Control: Loose Coupling Between Energy Expenditure And Energy Intake
- The Proceedings of the Nutrition Society: Cross Talk Between Physical Activity And Appetite Control -- Does Physical Activity Stimulate Appetite?
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