Dr. J offers his irreverent, slightly irrelevant, but possibly useful opinions on health and fitness. A Florida surgeon and fitness freak with a black belt in karate, he runs 50 miles a week and flies a Cherokee Arrow 200.
Four recent studies have looked into that interesting relationship of exercise, hormones and appetite.
The first study compared 19 women, who either ran (nine) or walked (10) on one day and then sat quietly for one hour on the next day. Appetite-affecting hormonal levels were then obtained from blood samples. At that point, the women were offered an unlimited buffet. Prior studies have demonstrated that exercise increases our ghrelin levels, the hormone known to stimulate hunger. However, after these women ran, even though their ghrelin level became higher, they actually ate several hundred fewer calories than they had used during their running. The researchers felt that the reason for this was due to an increase in other hormones that initiate satiety or feeling full after eating. These hormones signal the body that it has taken in enough fuel and mute the effect of the circulating ghrelin. However, neither sitting nor walking changed the blood levels of these satiety hormones, resulting in the individuals who walked consuming more calories than they had utilized.
A second study examined the effects of moderate exercise on eating with formerly overweight, sedentary men and women. The researchers gave volunteers milkshakes with some containing tasteless maltodextrin, which added 600 calories, and others without maltodextrin that only had 246 calories.
As a baseline, before beginning the exercise program, the subjects ate more at the buffet lunch and throughout the rest of the day after drinking the higher-calorie shake than when they were given the lower-calorie version. However, after three months of the exercise program, the subjects consumed fewer calories throughout the day even when they had the high-calorie shake than when drinking the lower-calorie one.
The study conclusion was that exercise “improves the body’s ability to judge the amount of calories consumed and to adjust for that afterward,” according to head researcher Catia Martins, a professor at the Norwegian University of Science and Technology in Trondheim. Martins concluded, “You need to stick with the program for several months to truly fine-tune appetite control.”
Another study conducted at Purdue University looked into the appetite-control effects of aerobic exercise compared to weightlifting. Researchers rated participants’ hunger 10 minutes after either aerobics or weightlifting, followed by the subjects eating 30 minutes later. The aerobic exercisers rated lower hunger and consumed fewer calories than the weightlifters. Their conclusion was that aerobic exercise reduced hunger ratings but weight lifting did not.
Finally, a fourth study from Brigham Young University confirmed that aerobic exercise is the best workout for adjusting food motivation. Researchers monitored the neural activity of both normal-weight and obese women while they looked at images of either food or flowers after a 45-minute period of hard aerobics. This exercise resulted in diminished brain responses to the food images, and an increase in total physical activity throughout the day for all the women regardless of body weight.
All of these studies demonstrate that aerobic exercise appears to help your body adjust to the amount of calories it really needs. For you to have this appetite control, however, you must make aerobic activity a consistent part of your healthy lifestyle.
No comments:
Post a Comment