Leptin is a protein hormone produced by your body that helps regulate weight by affecting your appetite, energy level, and metabolism. Usually, the amount of leptin you have is related to how much body fat you have: the more fat, the more leptin. An excess of leptin signals the body that it’s doesn’t need to eat. There have been some studies to see if individuals can become leptin resistant, and, as a result, overeat because their bodies don’t get the signal that there is already enough energy present.
The body tries to maintain a balance between the energy you take in (through calories in your food) and the energy you use (Total Daily Energy Expenditure). If you eat the same number of calories you burn, there is not change in weight. If you eat fewer calories than you need, you will lose weight, and if you eat more calories than you need you will gain weight.
The leptin hormone plays an important role in maintaining energy balance. Leptin is primarily produced by adipocytes, although smaller amounts are secreted by cells in the the stomach and placenta. Leptin production increases as the amount of body fat increases to let the body know that there is enough energy available.
The hormone acts on the hypothalamus in the brain. Higher levels of leptin cause a lower appetite, indicating that not as much energy needs to be taken in. This is different from feeling “full” while you are eating (called satiety) in that the action of leptin is over a longer course of time. Higher levels of leptin also cause an increase in metabolic rate, meaning you burn more calories.
There were some experiments with mice that suggested leptin might be a cure for obesity, in that leptin-deficient obese mice given the hormone rapidly lost weight and body fat. Unfortunately, obesity in humans isn’t caused by leptin deficiency. Obese people actually have higher levels of circulating leptin because of their higher levels of body fat. This suggested the theory of leptin resistance, in which obese individuals don’t respond to the hormone and continue to consume excess calories.
Effects of Leptin
Recent studies with overweight and normal with people showed a connection between the amount of circulating leptin and the percentage of body fat. There was a higher concentration of the circulating hormone in obese people than in those who were thinner.
In experiments with obese mice that were breed to not produce the hormone, injecting leptin resulted in a notable reduction in food intake within a few days and to an average 50% reduction in body weight within a month. The mice showed:
- Decreased hunger and food consumption
- Increased energy expenditure
Starvation has negative effects on reproductive function. As an example, women who have very low levels of body fat often cease having menstrual cycles. Also, the onset of puberty has been correlated with body condition as well as age. These effects are due in part to the hormone’s ability to enhance the production of gonadotropin-releasing hormone, and as a result the luteinizing and follicle-stimulating hormones from the anterior pituitary.
Prepubertal mice treated with leptin not only became thin, but also reached reproductive maturity earlier. There are people with inactivating mutations in the leptin receptor that are not only are obese, but also failed to achieve puberty.
So what does all this mean?
It means the more fat you have, the more leptin will be produced and available, so you can burn off the fat. But here’s the catch: as you burn off body fat, your leptin levels decrease! So the more fat you lose, the harder it gets to keep losing. But there are some things you can do to help:
Limit sugar and simple carbs. There’s some evidence that high glycemic index carbohydrates and sugar can inhibit leptin receptors. It also spikes your insulin, which can interfere with leptin production.
- Don’t restrict calories too much, you don’t want your body to think it’s starving. If don’t get enough nutrients, your hormones can get out of balance.
- If you are restricting calories, especially carbs like in the Atkins diet, and your weight loss slows or stops, you might need a refeed day. Extra carbs can replenish glycogen and give your metabolism a jolt. Eat an extra 100 -150% more carbohydrates than normal on one day and then resume your diet.
- Don’t yo-yo diet. Pick a healthy diet you can eat consistently. Make what you eat your lifestyle and not a “diet”. You don’t want to go through periods of severe calorie restriction followed by feasting where you gain the weight back; that will play havoc with your hormones.
- Get enough protein first thing in the morning. This will help stimulate leptin production as well as keep you feeling full longer.
- More Omega-3 fatty acids and less Omega-6. Omega-3 fatty acids can increase your body’s sensitivity to leptin and area also good for your heart and cholesterol levels. Most fish is a good source of Omega-3s, as are grass fed meats, chia seeds and flax seeds. Stay away from Omega-6s, they can lead to inflammation and reduce leptin levels overall.
- Make sure you get enough zinc. People with leptin deficiencies often seem to have a zinc deficiencies too. Look to foods like spinach, beef, lamb, seafood, nuts, cocoa, beans, and mushrooms, or consider a zinc supplement.
- Try to manage stress. Cortisol, often called the “stress hormone” inhibits the function of leptin,a s well as many other hormones.
- Make sure you get enough sleep. Lack of sleep not only decreases leptin levels, it actually increases ghrelin, the hormone that makes you hungry!
- Don’t do too much cardiovascular exercise. Seems contrary, but too much cardio can increase cortisol levels, oxidative damage, systemic inflammation, depress the immune system, and lower fat metabolism.