Leptin is a hormone produced by fat cells that helps to regulate body weight, energy expenditure and food intake. Typically, leptin serves to suppress appetite and increase metabolic rate. During starvation, a decline in leptin spurs appetite and promotes weight gain. However, when excessive weight gain occurs, leptin levels increase but do not always reduce food intake.
Leptin Resistance
As you might expect, people who have a genetic leptin deficiency become obese unless they are treated with leptin. However, this condition is extremely rare. More often, obese individuals actually have high levels of circulating leptin, but their bodies don’t respond to it appropriately. This phenomenon is leptin resistance. The exact causes of leptin resistance are still unclear, but diet almost certainly plays a role.
Calories
Excess calorie intake may promote leptin resistance indirectly by causing weight gain. Obesity is associated with leptin resistance in both animals and humans. On the other hand, severe caloric deficits, such as those required by some diet regimens, can lead to dramatic drops in leptin production, which have the undesired effect of stimulating appetite. The best strategy for maintaining normal leptin sensitivity while attempting to lose weight is to reduce caloric intake gradually.
Fat
High-fat diets tend to be high in calories, but dietary fat intake may contribute to leptin resistance independent of calorie intake. In an article published in “Nutrition Research Reviews” in 2010, Hariri et al. report that a number of research studies have indicated that mice fed high-fat diets for a long period of time were less responsive to leptin than mice fed low-fat diets. Because most studies of leptin resistance have been carried out in animals, it is not yet clear whether their findings extend to humans.
Protein
Whereas high-fat diets may decrease sensitivity to leptin, there is some evidence that high-protein diets have the opposite effect. In their 2005 study in “The American Journal of Clinical Nutrition,” Weigle et al. found that a diet providing 30 percent of total calories from protein and 20 percent from fat resulted in reduced appetite and body weight and increased leptin sensitivity, compared with a diet providing only 15 percent of calories from protein and 35 percent from fat.
References
- “Biochimica et Biophysica Acta”; Implications of Crosstalk Between Leptin and Insulin Signaling During the Development of Diet-Induced Obesity; C.D. Morrison et al.; 2009
- “Newswire”; The Rockefeller University; Topic: Leptin
- “Annals New York Academy of Sciences”; Leptin Signaling, Adiposity, and Energy Balance; Eric Jequier; 2002
- “Nutrition Research Reviews”; High-Fat Diet-Induced Obesity in Animal Models; Niloofar Hariri and Louise Thibault; 2010
- “American Journal of Clinical Nutrition”; A High-Protein Diet Induces Sustained Reductions in Appetite, Ad Libitum Caloric Intake, and Body Weight Despite Compensatory Changes in Diurnal Plasma Leptin and Ghrelin Concentrations; D.S. Weigle et al.; 2005
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