Exercise is medicine: exercise and appetite.
Article Type: Report
Subject: Appetite disorders (Care and treatment)
Appetite disorders (Research)
Exercise (Health aspects)
Authors: Teta, Jade
Teta, Keoni
Pub Date: 01/01/2012
Publication: Name: Townsend Letter Publisher: The Townsend Letter Group Audience: General; Professional Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2012 The Townsend Letter Group ISSN: 1940-5464
Issue: Date: Jan, 2012 Source Issue: 342
Topic: Event Code: 310 Science & research
Geographic: Geographic Scope: United States Geographic Code: 1USA United States
Accession Number: 276901144
Full Text: The "eat less, exercise more" approach to weight loss is more complicated than it appears. This is because human physiology works in direct opposition to this approach. When we exercise more, the natural compensatory reaction of the body is to eat more; and when we exercise less, the body responds by burning less.

[ILLUSTRATION OMITTED]

To achieve lasting weight loss, appetite must be managed. And to help control the compensatory eating that occurs with exercise, it is helpful to know what type of exercise to use to provide the best impact on calorie use, hormonal balance, and appetite control.

Appetite-Signaling Molecules

The two most important appetite-regulating hormones are leptin and ghrelin, and exercise affects both. (2-6) Leptin is produced in the fat cell and acts like the body's fuel gauge, communicating to the brain how much fuel (fat) it has in it tanks (adipose tissue). Rising leptin levels shut off hunger and stimulate metabolism via thyroid and adrenal stimulation. Falling leptin levels induce appetite and slow metabolism.

One confusing addendum to this mechanism is that when leptin levels are very high for long periods of time, leptin resistance sets in. This means that both very high and low levels of leptin can cause increased hunger and slowed metabolism. Leptin is usually thought of as a day-to-day appetite regulator.

Ghrelin is made in the stomach and controls hunger hour to hour. When ghrelin is high, we get hungry and crave highly palatable foods. When ghrelin is low, hunger dissipates. Ghrelin, like leptin, is affected by exercise.(2), (4), (5)

Glucose-dependent insulinotropic peptide (GIP), peptide YY (PYY), and glucagon-like peptide-1 (GLP-1) are all gut-derived signaling molecules that control appetite. These gut "hormones" are part of the enteroendocrine system helping relay information from the digestive system to the brain. They also all seem to be affected by exercise. (1)

Another consideration is the impact of stress hormone production during exercise. Stress hormones, in particular Cortisol, may play a role in increasing not only hunger but cravings as well.(10) Higher-intensity, shorter-duration (e.g., sprinting) exercise and longer-duration, moderate-intensity exercise (e.g., jogging) both raise Cortisol levels, but short, intense exercise is unique because it also suppresses ghrelin and is balanced by growth promoters.(5), (9) Low-intensity walking, especially in natural settings, lowers Cortisol. (13)

Exercise, Appetite and Hormones

Research hints that longer-duration moderate-intensity exercise, such as aerobic zone biking, swimming, and running, generates increased appetite shortly after exercise, and this mechanism may work through decreasing leptin and raising ghrelin, while higher-intensity, short-duration activity, like sprinting and interval training, may have a short-term appetite-suppressing effect by lowering both leptin and ghrelin. (2-5), (8)

Low-intensity walking seems to have a neutral impact on appetite and may be the only type of exercise wherein there is little to no hunger and craving compensations. (7), (11) It is important to distinguish between lower-intensity "leisure walking" and high-intensity "power walking." A 2004 study published in the American Journal of Clinical Nutrition showed that low-intensity walking (40% of V02 max) vs. high-intensity walking (70% of V02 max) had less of an impact on appetite despite burning the same number of calories per session (350 kcal/session). (7)

Leisure walking resulted in significantly less eating compensation following exercise compared with power walking (25% vs. 41%). The compensation in the power-walking group was almost enough to completely abolish the calories burned during exercise; as stated by the researchers: "increasing exercise intensity ... leads to an increase in energy intake during the meal that follows the exercise session ... sufficient to almost completely compensate for the exercise-induced energy expenditure."

Exercise and Appetite Compensation

Church et al. in the February 2009 issue of PLos ONE showed how important exercise's impact on weight loss can be. (12) in this study, the researchers had participants exercise at the recommended calorie expenditure advocated by the NIH of roughly 18 kcal per pound per week (136 minutes of exercise/week). They then had 2 other groups exercise to burn calories 50% below (72 minutes' exercise per week) and 50% above (194 minutes' exercise per week) this level. A fourth group acted as the control and did no exercise. The study continued for 6 months.

The group exercising at the highest level (194 min/week) lost less than half the weight that would be predicted based on energy expenditure equations. The "less exercise group" (72 min/week) lost more weight than predicted. The 8 kcal per pound per week group (136 min/week) lost about what was predicted. The researchers, while careful in the wording of their conclusion, believed that compensatory eating was the most likely culprit for the observed effect. They summed it up this way: "While we cannot conclude that an increase in energy intake in response to increased energy expenditure is the source of the observed compensation, based on the work of others we conclude it is the most likely cause."

Final Thoughts

There is more research to be done on exercise and appetite, but studies are providing clues. Duration or total amount of exercise may be the most salient issue to controlling appetite compensations. Short, intense exercise, as well as very low-intensity exercise like walking, seem to be most beneficial in controlling eating compensations induced by exercise. Exercising too much and/or for too long may result in compensatory reactions that could sabotage weight-loss efforts through increasing how much patients eat and what types of foods they choose.

Notes

(1.) Martins et al. Effects of exercise on gut peptides, energy intake and appetite. J Endocrinol. 2007; 193:m251-258

(2.) Broom et al. Influence of resistance and aerobic exercise on hunger, circulating levels of acylated ghrelin, and peptide YY in healthy males. Am J Physiol. 2009;296(10):R29-R35.

(3.) Karamouzis et al. The effects of marathon swimming on serum leptin and plasma neuropeptide Y levels. Clin Chem Lab Med. 2002;40(2);132-136.

(4.) Plinta et al. The effect of three-month pre-season preparatory period and short-term exercise on plasma leptin, adiponectin, visfatin and ghrelin levels in young female handball and basketball players. J Endocrinol Invest. Epub October 2011.

(5.) Erdmann et al. Plasma ghrelin levels during exercise - effects of intensity and duration. Regul Pept. 2007;143(1-3):I27-135.

(6.) Guerra et al. Is sprint exercise a leptin signaling mimetic in human skeletal muscle? J Appl Physiol. 2011;111 (3):715-725.

(7.) Pomerleau et al. Effects of exercise intensity on food intake and appetite in women. Am I Clin Nutr. 2004;80120-81236.

(8.) Bozinovski et al. The effect of duration of exercise at the ventilation threshold on subjective appetite and short-term food intake in 9 to 14 year old boys and girls. Int I Behav Nutr PhysActiv. 2009:6:66.

(9.) McMurray et al. Interactions of metabolic hormones, adipose tissue and exercise. Sports Med. 20O5;35(5):393-4T2.

(10.) Epel et al. Stress may add bite to appetite in women: a laboratory study of stress-induced Cortisol and eating behavior. Psychoneuroendocrinology. 2001; 26(1 ):37-49

(11.) Unick et al. Acute effect of walking on energy intake in overweight/obese women. Appetite. 2010;55(3):413-419.

(12.) Church et al. Changes in weight, waist circumference and compensatory responses with different doses of exercise among sedentary, overweight postmenopausal women. PLoS ONE. 2009;4(2):e4515

(13.) Park et al. The physiological effects of Shinrin-yoku (taking in the forest atmosphere or forest bathing): evidence from field experiments in 24 forests across Japan. Environ Health Prev Med. 2010;15(1 ):18-26.

by Jade Teta, ND, CSCS, and Keoni Teta, ND, LAc, CSCS jade@metaboliceffect.com | keoni@metaboliceffect.com
Gale Copyright: Copyright 2012 Gale, Cengage Learning. All rights reserved.