Where is it released from?
Leptin, sometimes referred to as the ‘starvation hormone’ or ‘fat controller’, is a hormone produced in the body’s fat cells. It signals to the brain, (the hypothalamus) that we have enough fat, so we eat less or stop eating.
What is its main function?
Leptin’s main function is to regulate body weight, helping to maintain what we may consider to be our optimum body weight and health. It’s closely linked to managing our energy intake through hunger and metabolism; as leptin levels increase in the body, so does metabolism.
The amount of leptin released is directly related to the amount of fat cells in the body - the more fat we have, the more leptin we typically have circulating in our blood. Leptin increases when our body’s fat content increases, leptin decreases when our body’s fat content decreases. One could say, the more leptin, the more chance of weight loss. Simple? Not always. Leptin isn’t working alone and its function is imperative to understand, especially if you relate to compulsive dieting or have often found yourself losing weight successfully, only to put it all back on again. Leptin works together with ghrelin to help shape our appetite and hunger signals. It doesn’t necessarily affect the food we ingest at every meal but instead intends to adjust how and what we eat to help manage our energy output, long term. It does this simply by signaling to our brain that we’re full, so we stop eating at an optimum time for our bodies needs.
What are the effects of imbalances in this hormone?
It would seem for someone that is overweight, that it would be as simple as leptin levels communicating that there is enough fat in the body, so this would promptly stop the desire to eat. But it’s not as straightforward as that - leptin resistance is when the body has high levels of leptin but the brain doesn’t know about it. The communication channel breaks down so the body knows it has enough fat but the brain doesn’t. Appetite doesn’t drop at a time when the body is actually full, so as far as the brain is concerned, we’re still hungry. It could make us even hungrier, and the cycle continues. Spending too long in a state of restricting food however, can cause leptin levels to go too low - the body has no reason to produce leptin if food intake is minimal. This means it could be very easy to fall back into a trap of eating when not hungry as the body’s signals aren’t firing properly. Especially by not eating enough fat, we are potentially lowering our leptin and therefore also affecting our metabolism and fat-burning abilities.
What is its relationship to lifestyle, diet and stress?
Most people who go on a diet and lose weight, end up regaining that weight. That’s because when we diet, we are often eating less and therefore are storing less fat. This decreases the amount of leptin produced. But if your leptin levels go below your personal leptin threshold, your brain senses starvation. The body responds by starting processes that intend to drive leptin levels back up. One of these processes is the simulation of the vagus nerve which is our energy storage nerve - it too causes hunger and attempts to get leptin levels back into balance (even though we may already be full!). Dieting and food choices are very personal and unique to each individuals needs and ethics, but when it comes to hormone health - leptin and its partner in crime, ghrelin, are keys pieces in grasping our overall health puzzle. If we eat in a way that suits our individual needs, we can find the state of balance the body is designed to live and thrive in. Starving or punishing ourselves through food or overeating to suppress emotions, is not conducive to a balanced hormonal system or a balanced life. The repercussions are often not worth it, starving may make us lose weight quicker but the long term effects can be damaging. With overeating we don’t notice the effects immediately but they can creep up on us, a lot of the time without us even noticing any differences, inside or out.
Words by Amy Mabin
Read more of our Hormone 101 series: