Exercise produces a variety of changes in your body, some of which you can see -- losing fat, for example -- and some of which you cannot, like changes in hormone levels. Although testosterone is known for its involvement in the muscle-building process, there are many other hormones that respond to exercise, and not all responses are beneficial. Consult a doctor before beginning any exercise program.
Cortisol
Cortisol is a hormone that is triggered by stress, and it helps regulate energy levels in your body. In addition, cortisol aids in mobilizing and storing fat, depending on your body's energy needs. According to research from the October 2010 issue of the journal "Growth Hormone & IGF Research," high-intensity exercise, such as sprinting, increases cortisol levels, but high-volume training, such as endurance training, does not increase cortisol levels significantly.
Testosterone
Testosterone is a hormone that aids in muscle building and, according to research from the June 2009 issue of the "Journal of Clinical Endocrinology and Metabolism," can also aid in reducing body fat. Heavy resistance training can stimulate increases in testosterone levels, according to a study from the July 2010 issue of "Human Physiology."
Insulin-Like Growth Hormone 1
Insulin-Like Growth Hormone 1, also known as IGF-1, can increase your muscle mass and reduce your fat mass, according to the June 2009 issue of the Journal of Clinical Endocrinology and Metabolism." According to a study from the March 2011 issue of the "Journal of Strength and Conditioning Research," heavy resistance exercise can trigger increases in IGF-1.
Hunger Hormones: Ghrelin and Peptide YY
Exercise appears to have significant effects on hunger hormones, such as ghrelin, which increases appetite, and peptide YY, which suppresses appetite. Research from the January 2009 issue of the "American Journal of Physiology: Regulatory Integrative and Comparative Physiology" found that endurance and resistance exercise caused reductions in ghrelin, while only endurance exercise caused peptide YY to increase. This suggests that endurance exercise may be better at suppressing appetite than resistance exercise.
References
- University of New Mexico; Cortisol Connection: Tips on Managing Stress and Weight; Christine A. Maglione-Garves, Len Kravitz, Ph.D., and Suzanne Schneider, Ph.D.:
- "Growth Hormone & IGF Research"; Effect of High- and Low-Intensity Exercise and Metabolic Acidosis on Levels of GH, IGF-1, IGFBP-3 and Cortisol; P. Wahl, et al.; October 2010
- "Journal of Clinical Endocrinology and Metabolism"; Testosterone and Growth Hormone Improve Body Composition and Muscle Performance in Older Men; F.R. Sattler, et al.; June 2009
- "Fiziologiia Cheloveka"; Acute Testosterone and Cortisol Responses to High Power Resistance Exercise; A.C. Fry, C.A. Lohnes; July 2010
- "Journal of Strength and Conditioning Research"; Recovery after Heavy Resistance Exercise and Skeletal Muscle Androgen Receptor and Insulin-Like Growth Factor-I Isoform Expression in Strength Trained Men; J.P. Ahtiainen, et al.; March 2011
- "American Journal of Physiology: Regulatory Integrative and Comparative Physiology"; Influence of Resistance and Aerobic Exercise on Hunger, Circulating Levels of Acylated Ghrelin, and Peptide YY in Healthy Males; D.R. Broom, et al.; January 2009
