Leptin is a naturally occurring protein that is synthesized in the body by adipocytes, or fat cells. Acting as an agent of the endocrine system, leptin is the hormone that, when eating, tells the brain that the stomach is satiated, or full. Studies have suggested that leptin and weight loss are connected and that by increasing one’s leptin levels, one can lose weight naturally due to a suppressed appetite. A limitation of this idea, however, is that everyone manufactures leptin and that obese individuals may therefore be resistant to its action, experiencing an interruption in the signal between leptin and the brain.
Composed of 167 amino acids, leptin is largely synthesized by a type of stored body fat known as white adipose tissue that can be used for energy and also aids in the maintenance of body temperature. Upon eating, leptin is liberated from the adipocytes into the bloodstream, which then carries it to the brain. Traversing the blood-brain barrier, this hormone makes its way to the hypothalamus, which is the section of the brain that controls appetite.
By binding to receptors in the hypothalamus, it can send the message that it is time to stop eating. If there were no leptin, the brain would perceive the body to be starving and constantly seek out more food. Without leptin, weight loss would be virtually impossible.
The fairly recent idea that leptin and weight loss are linked was borne of this understanding of leptin’s role in the body. Noting that individuals with a greater amount of stored body fat have more leptin circulating in the body at any given time, it is believed that increasing leptin’s effectiveness rather than its concentration in the bloodstream can have the effect of reducing appetite. This is because studies have suggested that some people have a leptin resistance, much like diabetics have a resistance to insulin.
Obese individuals have a large amount of leptin in their bodies, which suggests that the effect of leptin on the brain is somehow diminished. Therefore, newer research is looking into ways to reverse this resistance. If science can find a way to lower a patient's resistance to leptin, weight loss for these individuals becomes achievable.
One recommended strategy for accomplishing this is to get more sleep, as sleep deprivation has been shown to lower leptin levels in the bloodstream. Similarly, as leptin is linked to the body’s stress response, with leptin-resistant individuals demonstrating increased adrenaline levels, strategies for reducing stress may be indicated to improve one’s response to leptin. Leptin and weight loss are also linked in the sense that leptin-resistant individuals are said to have underperforming thyroids and increased cravings for sweet carbohydrate-based foods. Therefore, addressing leptin resistance may in turn help to eliminate these causes of weight gain.