A complex array of hormones -- including PYY, leptin and insulin -- control appetite. Such chemicals directly regulate feelings of fullness and indirectly affect body weight. Manipulating these hormones by changing behavior and improving diet can trigger weight loss, yet such changes also might cause unwanted side effects. People should, therefore, pursue this only after speaking with a health care professional.
Fat Intake
The body requires nutrients obtained from the diet to manufacture hormones. Thus, dietary changes can directly affect hormone levels. A 2006 investigation described in the journal "Endocrinology" tested the impact of fat content on internal biochemistry in laboratory animals. Rats received a low-fat or high-fat diet for 112 days. The low-fat diet increased levels of the gut hormone PYY and decreased body weight. This substance causes feelings of satiety, so the authors speculated that the rats in the low-fat condition felt more full and thus ate less. It is unclear, however, if similar results would occur in humans.
Cycling Exercise
Physical activity also changes the body's chemistry. Both acute and chronic exercise, for example, trigger hormones affecting body mass index. A 2010 paper in the journal "Appetite" looked at the possible effect of cycling exercise on hormone release. Healthy males participated in a pair of three-day protocols: exercise and no exercise. The men manufactured more PYY and less insulin during the exercise portion of the experiment. Such changes are typically associated with a reduction in body weight. While suggestive, the short duration of this experiment makes it difficult to draw firm conclusions about the long-term impact of exercise on hormone production.
Pregnancy and Exercise
Changes in lifestyle also alter hormone production in pregnant women. A 2010 report in "Clinical Endocrinology" assessed the effect of physical exercise during the third trimester. Relative to a control group, active pregnant women showed greater levels of leptin immediately prior to birth. Interestingly, these increases reduced the body weight of both the women and their offspring. Making changes during pregnancy can cause stress, which can have an adverse effect on the unborn child. Thus, pregnant women should speak with a doctor before changing their habits.
Ambient Temperature
People might be able to control their leptin levels through other means as well. Environmental temperature, for example, can affect hormone synthesis and release. A 2010 study in the "Journal of Endocrinology" tested the effect of different ambient temperatures on laboratory animals. Rats were exposed to either tepid room temperatures or cold temperatures. The rodents maintained in the colder room had greater levels of leptin, ate less and lost weight. These results suggest that living in colder climates might trigger weight loss, yet such a hypothesis requires additional testing, especially in human subjects.
References
- "Understanding Normal and Clinical Nutrition"; Sharon Rady Rolfes et al; 2008
- "Endocrinology"; "Attenuated Peptide YY Release in Obese Subjects is Associated with Reduced Satiety"; Carel Le Roux et al; January 2006
- "Appetite"; "Impact of Exercise and Dietary Fatty Acid Composition From a High-Fat Diet on Markers of Hunger and Satiety"; Jamie Cooper et al; Oct. 28, 2010
- "Clinical Endocrinology"; "Effects of Exercise Training on Maternal Hormonal Changes in Pregnancy"; Sarah Hopkins et al; Dec. 24, 2010
- "Journal of Endocrinology"; "Nutritional and Environmental Factors Affecting Plasma Ghrelin and Leptin Levels in Rats"; Keiko Nakahara et al; October 2010
