Aerobics increases blood protein that may suppress appetite

Three months of aerobic exercise decreased body fat and calorie intake in overweight and obese people, according to a new study, and the researchers believe that changes to a central nervous system factor are responsible. The results will be presented at The Endocrine Society's 90th Annual Meeting in San Francisco.

A research team at the University of Chile Clinical Hospital in Santiago, led by A. Veronica Araya, MD, assistant professor, showed that decreased food intake and reduced body mass index (BMI), a measure of body fat, were linked to increased levels of a protein called brain-derived neurotrophic factor, or BDNF. Its main role is promoting the growth and survival of nerve cells, according to Araya.

However, recent evidence shows that BDNF also is related to obesity and metabolism. The authors speculated that it could suppress appetite.

The team evaluated blood levels of BDNF before and after a three-month program of aerobic exercise in 15 overweight or obese men and women. The seven men and eight women, ages 26 to 51, worked out on a treadmill and bicycle. They were asked about their calorie intake and told to continue eating their usual number of calories. The participants were unaware that one of the study's objectives was to evaluate changes in food intake.

At the end of the study, the subjects had decreased BMI, waist circumference, and blood pressure, the data showed. They also reported consuming fewer calories than at the beginning of the study. Over the three months, BDNF levels greatly increased. This higher the concentration of BDNF, the less the subject's intake of calories and the greater the weight loss, Araya said.

Thus, it is possible that increases in BDNF suppress appetite, she said. They did not test appetite suppression directly, but some past studies have shown that aerobic exercise suppresses appetite.

"It is important to clarify the factors involved in the response to different weight loss therapies," Araya said, "because we could find a marker to predict response to the intervention."

For instance, the marker, such as BDNF, might help healthcare providers select who will benefit from exercise, she explained.