A new study finds that exercise increases both hunger and satiety, and that the magnitude of this effect differs from person to person. The researchers said their findings might explain why exercise helps some people lose weight better than others.
The study involved 58 overweight and obese adults who undertook an exercise regimen. The researchers found that exercise tended to increase the participants’ hunger before a meal, compared with their appetite on more sedentary days. However, the participants were also more easily satisfied by their meal than before they had become active.
Both effects were observable across the entire study group, but there were slight differences between participants who had lost weight and those whose extra pounds stubbornly remained.
In general, exercisers who did not achieve their expected weight loss were both hungrier after fasting (right before breakfast) and throughout the day, compared with their hunger ratings at the beginning of the study.
Meanwhile, those who had more successfully lost weight typically saw their fasting, pre-breakfast appetites increase after becoming active, but were not hungrier throughout the day.
“The reason that some people are more successful (at weight loss) could be due to a lesser increase in appetite and the prevention of an increase in food intake,” said lead researcher Dr. Neil King, an associate professor at Queensland University of Technology in Brisbane, Australia, during an interview with Reuters.
Dr. King said the study shows that new exercisers should not give up if they begin to feel hungrier than normal, or fall short of their weight loss goals.
Indeed, separate research has found that the health benefits of exercise, including improved cardiovascular fitness, lower blood pressure and cholesterol levels, are present even in the absence of significant weight loss.
For Dr. King’s study, his team had 58 overweight men and women undertake a 12-week supervised exercise routine designed to burn 500 calories per session.
At the beginning and end of the study, the participants rated their hunger before eating a breakfast of cereal and toast. They reported their hunger ratings again immediately after the breakfast and throughout the rest of the day.
After 12 weeks, 32 participants had shed the expected amount of weight based on the calories they burned during exercise, while 26 participants had not.
And while both groups showed, on average, a boost in appetite before breakfast at the end of the study, the daily reported hunger was greater among those who had not seen a substantial weight loss.
But both groups of exercisers seemed to be more readily satisfied by their breakfast than they had been before starting the exercise regimen.
The study shows that “the effect of exercise on appetite regulation involves at least 2 processes: an increase in the overall drive to eat and a concomitant increase in the satiating efficiency of a fixed meal,” the authors of the study concluded.
The researchers said the reason behind these two different appetite effects of exercise is not yet clear. Perhaps physical activity, while boosting hunger, may also increase the sensitivity of the body’s fullness-signaling system, they said.
“The key messages…are exercise is good for you, don’t expect unrealistic weight loss and don’t give up exercising just because of lower-than-expected weight loss,” Dr. King said.
The study was published in the October 2009 American Journal of Clinical Nutrition.
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