Exercise reduces hunger in lean women but not obese women

Exercise does not suppress appetite in obese women, as it does in lean women, according to a new study. The results were presented Tuesday, June 17, at The Endocrine Society's 90th Annual Meeting in San Francisco.

"This [lack of appetite suppression] may promote greater food intake after exercise in obese women," said Katarina Borer, PhD, a University of Michigan researcher and lead author of the study. "This information will help therapists and physicians understand the limitations of exercise in appetite control for weight loss in obese people."

Borer and her co-workers sought to better understand how changes in body fat level influence appetite and a hormone called leptin, which in animals curbs appetite when body fat increases. When leptin levels rise, it supposedly shuts off appetite and motivates physical activity to burn calories. However, as obese people become fatter, their leptin levels rise, but they become resistant to the actions of this hormone.

"The hormone doesn't do the job it's supposed to do in lean people," Borer said.

In research funded by the National Institutes of Health, Borer's group studied 20 postmenopausal women: 10 lean and 10 obese women. The women ate three weight-maintenance meals a day while participating in three experiments on three separate days. During one experiment they did not exercise.

In the other two experiments the women exercised on a treadmill in the morning and the afternoon. They burned 500 calories each time, for a total of 1,000 calories a day. These two experiments differed by exercise intensity. One involved walking at high intensity, or 80 percent of maximal effort, for 7.5 minutes, with 10-minute rest periods between 10 walking sessions. The other experiment was half as intense (40 percent of peak effort) and involved walking for 15 minutes and resting for 5 minutes.

Every hour and before each meal, subjects recorded their appetite level on a 10-point scale ranging from not at all hungry to extremely hungry. Blood samples were collected every 15 to 60 minutes for hormone measurements.

Obese women claimed they were less hungry than lean women before meals and reported no appetite suppression during exercise, Borer said.

As expected, obese women had much higher leptin levels than in lean women, study data showed. But during intense exercise, obese women did not have reduced production of leptin, as lean women did. Only moderate-intensity exercise lowered leptin in obese women.

"Obesity interferes with leptin's detection of exercise energy expenditure and with appetite suppression," Borer said. "Obese women perhaps need to consciously watch their calories because some of the hormonal satiety [fullness] signals don't seem to work as well."

Source: The Endocrine Society

Related stories:

New master switch found in the brain that regulates appetite and reproduction
Body weight and fertility have long known to be related to each other – women who are too thin, for example, can have trouble becoming pregnant. Now, a master switch has been found in the brain of mice that controls both, and researchers at the Salk Institute for Biological Studies say it may work the same way in humans.
Eating junk food whilst pregnant and breastfeeding may lead to obese offspring
Mothers who eat junk food during pregnancy and breastfeeding may be putting their children at risk of overeating and developing obesity, according to a study funded by the Wellcome Trust and carried out at the Royal Veterinary College, London. The research suggests that pregnant and breastfeeding women should not indulge in fatty, sugary and salty foods under the misguided assumption that they are "eating for two".
Hormone that signals fullness also curbs fast food consumption and tendency to binge eat
The synthetic form of a hormone previously found to produce a feeling of fullness when eating and reduce body weight, also may help curb binge eating and the desire to eat high-fat foods and sweets. The findings on fast food consumption and binge eating tendencies are based on a 6-week research study of 88 obese individuals.
Overweight men face higher risk of dying of prostate cancer
(PhysOrg.com) -- Prostate cancer patients who are overweight and have elevated insulin levels are much more likely to die of the cancer than other patients, say researchers at Harvard University and McGill University. Their research is published in the October issue of The Lancet Oncology.
Mental barriers hamper obese women's efforts to get exercise
For arachnophobes, it's difficult to kill a spider as it scurries across the floor. Those who are scared to fly might not ever set foot on a plane. While nothing physically stops people with these aversions, a mental barrier can keep them from the task at hand.
How much are you really exercising?
People struggling with obesity often underestimate how many calories they are actually consuming, which can hinder weight loss efforts. It should follow that the same person would overestimate the amount of exercise they're doing, right?
New study indicates link between weight gains during pregnancy and dieting history
Women who have a history of dieting or other restricted eating practices are at risk of gaining an inappropriate amount of weight during pregnancy. In a study published in the October 2008 issue of the Journal of the American Dietetic Association, researchers from the University of North Carolina at Chapel Hill report that restrained eating behaviors prior to pregnancy were associated with weight gains above the Institute of Medicine recommendations for normal, overweight and obese women, and weight gains below the recommendations for underweight women.
Scientists discover why a mother's high-fat diet contributes to obesity in her children
New research published online in The FASEB Journal suggests that pregnant women should think twice about high-fat foods. In a study from the University of Cincinnati and the Medical College of Georgia, scientists found that female mice fed high fat diets were more likely to have oversized offspring (a risk factor for overweight and obesity) because fat causes the placenta to go into "overdrive" by providing too many nutrients to the fetus. This information also suggests that the reverse may be true as well—high fat diets may help prevent undersized babies.

News discussion:

Medicine & Health news