We understand that when our food intake drops in order to create a caloric deficit that leptin also drops. Not much has been said about exercise when referring to the deficit we must create in order to lose fat. Whether its caloric restriction or exercise, it doesn’t appear to have much of an effect on how much leptin drops. The body senses that energy availability is dropping, and begins adjusting things metabolically. Exercise still plays plenty of other roles in terms of dieting and fat loss. We’ll discuss that at some point soon.
Leptin interacts with various part of the brain, but the hypothalamus where the set point is primarily thought to be regulated appears to be the main area. When leptin drops a bunch of other neurochemicals adjust, such as Neuropeptide Y (NPY), Agouti Related Peptide (AgRP), Pro-opiomelanocortin (POMC) and Cocaine Activated Receptor Transcript (CART). When these hormones adjust, they cause other changes that affect all aspects of metabolism.
There are other regulators as well,such as brain dopamine levels go down when leptin goes down, and this appears to play a role in the overall metabolic adaptation to dieting. Dopamine as well as POMC/AGRP/NPY/CART all regulate things like metabolic rate, which is lowered during dieting, appetite/hunger, which goes up during dieting, activity levels often drop as lethargy sets in due to lowered calories, hormone levels of testosterone and thyroid drop as does nervous system output, and cortisol rises. These reason are a big part of why dieting gets so much harder as people get leaner.
Basically, the body undergoes an overall adaptation that attempts to slow fat/weight loss and prompts us to seek out food. These adaptations become stronger the leaner the individual gets. Leptin directly impacts on how well or how poorly other appetite hormones in the body send their signals to the brain. Cholecystokinin (CCK) is a hormone released from the gut primarily in response to protein or fat intake, It’s involved in making you feel full after a meal. It doesn’t work as well when leptin levels drop due to dieting.
Competitive bodybuilders and figure/fitness competitors know that even if they do everything they can with their calories per meal, like lots of lean protein, moderate fat, fiber, moderate amounts of low GI carbs, they simply won’t feel full for very long. The reason being is that none of the body’s signals are working very well.
Leptin is essentially letting the brain know in terms of how it responds to other signals. The hormones that determine when you get hungry or full aren’t working as well when leptin is lowered from dieting and fat loss. Leptin certainly isn’t the only hormone involved in all of this; but it’s definitely one of the most important ones.
This article was researched and written by Follow @MattToronto1