There are no dog foods containing leptin available for purchase. Leptin cannot be processed through the intestines, although it can be injected. Leptin is a hormone that aids in the feeling of satiety. It inhibits hunger and regulates energy. In obese animals, cells are constantly secreting leptin and the body becomes immune to it, according to Wikipedia. Some schools of thought suggest that eating foods that help lower or raise one's natural leptin levels can help to regulate weight.
Neither feeding nor administering leptin to dogs or humans is approved by the FDA in the United States. Excessive leptin levels have been linked to obesity in animals and humans. When there is an abundance of leptin in the bloodstream, leptin sensitivity decreases. The excess leptin appears to slow the flow to the brain resulting in increased appetite and food cravings, along with decreased metabolic function. Some studies show a positive impact on both metabolism and cravings in rats injected with leptin, but the effect was lessened or reversed in some rats with pre-existing obesity. Although there may be some benefits to targeting leptin levels through diet, it is important to discuss any change to a pet's diet with a veterinarian first.