Exercise May Reduce Appetite But Increases Calorie Consumption

The relationship between exercise, appetite and food intake is a complex relationship.  Aerobic exercise has been touted as a way to reduce appetite potentially increasing weight loss.  This effect has been termed the anorexia of exercise.  The effect appears to be commonly found after exercising at greater than 60% of maximum oxygen consumption.  This decreased appetite after exercise has been  possibly due to the redistribution of blood flow from the gastrointestinal tract to the peripheral muscles.   However, a temporary reduction in appetite following exercise may not actually correlate with a reduced caloric consumption over a more extended period of time.

Derek Laan and colleagues from Purdue University and the University of Missouri recently published a further look at the relationship between exercise, appetite and caloric intake.  In addition to aerobic exercise, they examined the effect of resistance exercise on appetite and calorie consumption.  The key issues in the design of this study included:

• Subjects: Male and female from the Purdue community, ages 18 to 29, BMI between 18 and 29 (normal weight to overweight but obesity excluded), percent body fat less than 20% for men and less than 35% for women, not currently dieting with no recent weight loss/gain, nonsmokers, nondiabetic and exercising at least twice per week for 30 minutes in each of aerobic and resistance categories.
• Experimental Design: Three sessions: 1.) one aerobic session of 35 minutes cycling at 70% maximum heart rate, 2.) one resistance training session of 35 minutes including 3 sets of 5 weight lifting exercising at 75% maximum, 3.)  a control session of no exercise
• Appetite and Calorie Consumption:  1.) Perceived appetite rated before and after exercise using 13 point scale with 1=not at all hungry and 13=extremely hungry, 2.) Thirty minutes after exercise subjects were given 30 minutes to consume a pasta salad meal with instructions to eat as much or as little as desired until feeling comfortably full.

The key results of the research included:

• Aerobic exercise but not resistance exercise reduced hunger ratings 10 minutes after exercise.  The effect lasted about 30 minutes when hunger ratings returned to levels experience by resistance exercise and controls
• Mean caloric meal intake was 897 calories for aerobic exercise group, 924 calories for the resistance exercise group and 784 calories for the control group (both exercise groups consumed more than controls—14 to 18% more, a statistically significant amount

The authors concluded that in healthy adults, aerobic exercise does temporarily reduce hunger ratings but the effect is small, transient and not related to reduced calorie consumption in an unrestricted meal setting.  A similar study would be interesting in a group of patients with anorexia nervosa who commonly exercise to excess in an attempt to lose weight and maintain weight below medically healthy levels.   Additionally, similar studies in obese subjects might be helpful in prescribing the best exercise and diet regimens for weight loss.   This study suggests resistance training alone may increase caloric intake more than the calories expended in resistance exercise.   The increase caloric consumption with aerobic exercise probably contributes to the limited weight loss found in starting an aerobic exercise program.

Photo of March 2011 sunrise at Juno Beach, Florida courtesy of Yates Photography.

Laan DJ, Leidy HJ, Lim E, & Campbell WW (2010). Effects and reproducibility of aerobic and resistance exercise on appetite and energy intake in young, physically active adults. Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme, 35 (6), 842-7 PMID: 21164556