The Effect of an Acute Bout of Aerobic Versus Resistance Exercise on Ghrelin Levels in Obese Men

Abstract

INTRODUCTION: Obesity is a major public health problem worldwide. Over 33.3% of adults are obese, and increased hunger has been shown to be a cause of overeating and weight gain. In normal weight individuals, the hormone ghrelin is attenuated after food consumption, as well as after moderate exercise, and this is thought to promote satiety. However, ghrelin has been found to remain elevated in obese individuals after food consumption. Exercise is an effective lifestyle modification strategy used to decrease adiposity. PURPOSE: The purpose of this study was to examine the effects of aerobic and resistance exercise on ghrelin concentrations and hunger in obese men. METHODS: Eleven obese men (M±SD: Age: 30±9.6yr; BMI: 38.7±11.3kg.m2) performed aerobic and resistance exercise on nonconsecutive days. The subject criterion required males, 18yrs and older, non-diabetic, not currently exercising more than 3 days a week, and not currently taking beta-blockers, verapamil, or digitalis. The resistance exercise session involved 6 circuit exercises targeting the major muscle groups for 4 sets and 10 repetitions per set. The aerobic exercise session involved treadmill walking performed between 60-80% heart rate maximum (HRmax) for a time interval that mirrored the resistance exercise session. HRmax was calculated as 220-age. Blood samples were taken via venipuncture pre, immediately post and 45 minutes post-exercise for each session. Perceived hunger was quantified at the same time points with a 16-point scale (0-16). Serum was assayed to determine ghrelin concentrations with an ELIZA kit manufactured by RayBiotech, Inc. Two 2X3 repeated measures ANOVAs were performed to analyze the interactions between ghrelin and perceived hunger over three time points. RESULTS: Perceived hunger was found to have a significant difference over time (p<0.05). Perceived hunger was significantly higher 45min post exercise compared to baseline for both exercise types (M±SD: pre: 4.27±0.47; post: 4.73±0.51; 45min post: 6.14±0.67). No significant interaction or differences were found for ghrelin (ng/ml) between exercise protocols or across time (p >0.05)(M±SD: pre: 110.53±21.12; post: 120.32±27.32; 45min post: 113.02±20.16) CONCLUSION: Overall, there was no difference in ghrelin concentrations over time or between exercise protocols in obese men. A significant change in perceived hunger was found over time with an increase in hunger after exercise.