This is an excerpt from Physiology of Sport and Exercise 7th Edition With Web Study Guide-Loose-Leaf Edition.
Research Perspective 4.3
Does Environmental Temperature Alter the Hormones That Control Appetite?
The interactions among exercise, appetite, and energy intake are important for the control and maintenance of energy homeostasis and body weight. Scientifically, these interactions have received widespread attention because they may hold the key to treating excess weight gain and obesity. Leptin and ghrelin are hormones that regulate the perception of hunger and lead to changes in appetite. Leptin (the “satiety hormone”) decreases energy intake, while ghrelin (the “hunger hormone”) increases energy intake. Both exercise and exposure to extreme temperatures can affect the concentrations of these appetite-regulating hormones. Circulating ghrelin concentration and perception of hunger both decrease immediately after a single bout of moderate- to high-intensity exercise but have no influence on the total energy intake throughout the day. Environmental temperature has an impact on resting metabolic rate. Indigenous populations who live in polar climates have elevated basal metabolic rates, while those who live in tropical climates have decreased basal metabolic rates. Additionally, exercise in a hot environment reduces appetite, while exercise in the cold stimulates appetite; however, it is unknown if these effects involve changes in circulating leptin or ghrelin.
Recently, a group of researchers at the University of Nebraska Omaha conducted an experiment to examine how exercise in different environmental temperatures would affect the leptin and ghrelin responses to exercise.9 Research subjects completed three separate 1 h bouts of cycling in hot (33 °C [91°F]), neutral (20 °C [68 °F]), and cold (7 °C [45 °F]) air temperatures. The research team measured leptin and ghrelin in blood samples collected preexercise, immediately postexercise, and after a 3 h recovery. Similar to previous studies, circulating leptin was increased immediately after exercise and remained elevated 3 h later. Circulating ghrelin concentrations did not change. Although the researchers hypothesized that there would be larger increases in leptin after exercise in the heat and larger increases in ghrelin after exercise in the cold, there was no effect of air temperature on any hormone measurements. The conclusion from this study was that environmental temperature does not alter the leptin or ghrelin responses to short bouts of aerobic exercise. Future research studies are needed to determine what other variables might affect regulatory hormone and hunger responses following exercise in extreme environments.