Hungry? Go for a run instead
A tip dietitians and weight loss counselors often give to clients to help them eat less is to delay eating for time to ensure that the hunger felt is real, and not just a craving that can send your calorie intake over the limit. A new BYU study backs that up, with a twist. If you are feeling low on your motivation to diet, the key to curbing your appetite can be a few minutes of aerobic exercise.
Professors James LeCheminant and Michael Larson measured the neural activity, using EEG, of 35 women while they viewed 120 food images on two separate days – one in which they participated in morning exercise (45 minutes on a treadmill) and one where they did not. Eighteen of the women were of normal weight and 17 were clinically obese, meaning their BMI was greater than 30 (18.5 to 24.9 is considered normal; 25.0-29.9 is overweight). The participants also kept records of food consumption and physical activity on both experiment days.
On the days where the women exercised, they had lower brain responses to the food images. Also, according to their logs, the women who participated in brisk morning walk also kept up a greater level of total physical activity during the entire day. The same response held true regardless of the woman’s BMI.
As for those who believe that exercise will only increase your appetite, the researchers found the opposite to be true. The women did not eat more food on the exercise day to “make up” for the extra calories they burned. In fact, they ate approximately the same amount of food on the non-exercise day.
"The subject of food motivation and weight loss is so complex. There are many things that influence eating and exercise is just one element. (But) This study provides evidence that exercise … may affect how people respond to food cues," LeCheminant said.
A separate study, conducted in Australia, seems to back this theory up as well in men.
Researchers from the University of Western Australia divided 33 overweight, sedentary men into three groups. One group did aerobic workouts three times a week for 12 weeks. A second group did resistance training for the same amount of time. The remaining men remained sedentary during the study period.
The men were assessed for “perceived hunger and fullness” and had their levels of “appetite-related hormones” measured. Those who exercised aerobically ate less of a controlled meal than those in the other two groups, and reported feeling more full, despite all stating before eating that they had similar appetites (meaning they were all hungry, but those who participated in aerobic exercised felt full faster, potentially leading to less calorie intake during the day.
The researchers noted that the one big difference between the aerobic group and the resistance training group was the level of leptin, a hormone that plays a key role in regulating energy intake. Leptin acts on brain receptors where it inhibits the appetite through a pathway involving the hypothalamus. It signals the brain that the body has had enough to eat and produces a feeling of satiety. A lack of leptin leads to uncontrolled food intake and resulting obesity.
The morale of the story: Diet and exercise work together in many ways to help control weight. In addition to a healthy diet, include at least 30-45 minutes of moderate-to-vigorous activity, three to five times a week. Remember that resistance training may not curb your appetite, but it has a large role in weight management. Building muscle helps increase metabolism, helping your body more effectively burn excess calories.
Brigham-Young University News Release
Guelfi KJ, Donges CE, Duffield R., Beneficial effects of 12 weeks of aerobic compared with resistance exercise training on perceived appetite in previously sedentary overweight and obese men. Metabolism. 2012 Sep 6. [Epub ahead of print]