When it comes to weight (and the chronic conditions associated with having overweight), calories, carbohydrates and fat get a lot of attention, but many people tend to overlook the important role that hormones, like an increase of leptin, play. You have a lot of hormones in your body, but two, in particular, ghrelin and leptin, play vital roles in managing your weight.
Leptin, which is often nicknamed the "satiety hormone," is directly connected to your weight, and the amount of body fat you have. If leptin levels are low, it can lead to intense hunger or an inability to feel full. On the other hand, if leptin levels are high (a much more common occurrence), it can lead to leptin resistance, a condition in which the body no longer responds to the hormone effectively.
What Is Leptin?
Leptin is a hormone produced by and released from your fat, or adipose, cells. The main function of leptin is to regulate your energy balance, by sending signals to a part of your brain called the hypothalamus in an effort to help you maintain a healthy body weight. When leptin levels go up, it signals to your brain that you're full, and you should stop eating. When leptin levels go down, it tells your brain that you're hungry and that you should find food.
Because leptin is stored in your fat cells, changes in your body fat percentage have a direct effect on the amount of leptin in your body. If you gain body fat, your leptin levels increase. On the other hand, if you lose weight, and your body fat percentage goes down, leptin levels will also go down.
Leptin Versus Ghrelin
Another hormone, called ghrelin, has an effect that's opposite of leptin. Ghrelin, which is produced mainly in the stomach and small intestine, is known as the "hunger hormone." The main function of ghrelin is to stimulate the appetite, which triggers you to eat more and store more fat. According to the Hormone Health Network, ghrelin also plays an important role in releasing the hormone insulin and helps keep your heart healthy.
It would make sense to think that individuals living with obesity have higher levels of ghrelin, prompting them to eat more, but according to a July 2015 issue of Today's Dietitian, the opposite is actually true. Ghrelin levels aren't actually higher in people who are overweight, they're just more sensitive to the appetite-stimulating effects of the hormone (while also being less sensitive to the effects of leptin).
It seems almost as if the two hormones are in competition, but, in reality, they work together to keep your body at an optimal weight. In a healthy body, ghrelin helps ensure that you don't forget to eat and get too thin, while leptin lets you know when you're full, and it's time to stop eating. However, if ghrelin and leptin signaling is off or your body doesn't respond to the hormones properly, it can disrupt the brain signals and cause false hunger cues.
What Lowers Leptin?
When you are burning more energy than you're taking in, such as when you're working out a lot and/or on a weight-loss diet, and you begin losing body fat, this reduces the leptin levels in your body. Because you don't have as much body fat (and leptin is produced in fat tissue), your body physically can't produce the same amount of leptin. As a result, your brain is no longer getting the signal that you're full, and it's time to stop eating. This can lead to increased hunger that's hard to relieve, even at meal times.
This can be quite the paradox when you're trying to lose weight because as you're successfully burning off extra body fat and getting thinner, you have less fat to produce the leptin hormone, which tells you you're full. In other words, the leaner you are, the less leptin you have, which means your appetite isn't suppressed as much.
Have you ever gone on a diet and successfully lost weight for the first few weeks, and then gained it back quickly because your increased hunger made it difficult to stop eating? This may have been due to changes in your leptin levels, according to a report published in Metabolism in January 2015. Other things that reduce leptin levels include:
- Cold temperatures
- Thyroid hormone
Read more: How to Convince Your Body That It Needs Less Food
What Is Leptin Resistance?
But it isn't necessarily low levels of leptin that's the problem; it's an inability for your body to effectively respond to the leptin that it does have. This condition, which is characterized by decreased sensitivity to the signals that leptin sends to your brain reminding you that you have adequate fat for your energy needs and should stop eating, is called leptin resistance.
When the brain isn't correctly receiving the signals from leptin, you not only lose the appetite inhibiting benefit, but the brain also decreases your energy levels in order to conserve energy. As a result, you end up feeling hungry and less motivated to exercise: A double whammy when it comes to maintaining a healthy weight.
What Causes Leptin Resistance?
Obesity plays an important factor in the development of leptin resistance. Even though people with obesity have a lot more fat cells, and thus higher leptin levels than thin people, the ability of leptin to signal the hypothalamus is disrupted. According to the article in Today's Dietitian, this happens due to inflammation and an inability for leptin to bind with the leptin receptors in the brain.
When you have a lot of fat, especially belly fat, that fat produces inflammatory compounds called cytokines. These cytokines circulate through the blood and block the effects of leptin, leading to leptin resistance.
Diet and Leptin Resistance
Correcting how your body responds to leptin doesn't have as much to do with ways to increase leptin in your blood as it does with making sure your body is responding appropriately to the leptin that it does have.
In addition to your body weight, the foods you're eating can have a direct effect on how well your body responds to the hormone. According to a report published in AYRA Atherosclerosis in September 2014, high-glycemic carbohydrates, like sugar, white bread and white pasta, may cause leptin resistance, while choosing fiber-rich carbohydrate sources, like non-starchy vegetables, can decrease both leptin resistance and insulin resistance.
On the other hand, it appears that diets high in protein and fat increase sensitivity to leptin and help improve leptin resistance. In addition to boosting leptin levels directly, protein can also increase testosterone levels. Testosterone not only helps to prevent leptin resistance, but through building muscle in your body, testosterone can help you lose weight.
Connection Between Leptin and Testosterone
Leptin is inversely related to testosterone, or in other words, the higher your levels of testosterone, the lower your levels of leptin and vice versa. Because men have higher levels of the testosterone hormone, as a general rule, they tend to have lower leptin levels than women.
However, testosterone levels drop in men who live with obesity, giving way to higher leptin levels and an increased risk of leptin resistance. Because of this, a study published in December 2016 in the International Journal of Obesity dove into whether or not supplementing with testosterone could improve leptin levels. Researchers found that, when compared to control groups, men who were given testosterone supplements lost more weight and had better leptin levels.
Of course, this doesn't mean that you should supplement with testosterone as a quick fix for leptin resistance and abnormal levels, especially without talking to your doctor first.
Get Enough Exercise
In addition to balancing the amounts of macronutrients (carbohydrates, protein and fat) that you're eating and maintaining a healthy weight, exercise may have a direct effect on leptin levels and sensitivity to the hormone. According to one study published in African Health Sciences in December 2013, moderate aerobic exercise reduced the amount of inflammatory cytokines in participants living with obesity and type 2 diabetes and improved their leptin sensitivity.
Another study published in Medical Sciences in December 2018 backed up these findings and took it a step further by reporting that exercise not only improves leptin levels, it also increases the amount of another hormone called adiponectin.
Adiponectin acts as an anti-inflammatory compound and also helps protect you from heart disease by reducing the formation of plaque on the blood vessel walls and increasing the production of nitric oxide, a gas that increases blood flow and keeps your heart healthy. Adiponectin is also associated with decreased insulin resistance, type 2 diabetes and a lower risk of obesity.
Read more: 6 Weird Ways Early Birds and Night Owls Differ
Make Time for Quality Sleep
You may not think about sleep when it comes to your weight and/or your hormone levels, but getting enough quality sleep is vital to make sure that you have enough leptin in your body and that you're responding to the hormone effectively.
According to the National Sleep Foundation, when you're sleep-deprived, your leptin levels drop significantly while your ghrelin levels go up. In other words, a lack of sleep can leave you feeling hungrier and make you more likely to overeat. On the other hand, a good night's sleep can help balance your hormone levels.
The Centers for Disease Control and Prevention recommend that adults get at least seven hours of quality sleep every night. But the key word is quality. Make sure your bedroom is dark and quiet and free of any interruptions. Remove electronics from the bedroom and avoid caffeine, alcohol and eating large meals before bedtime. Develop a consistent sleep schedule by going to bed at the same time every night and wake up at the same time every morning.
- Metabolism: "Physiology of Leptin: Energy Homeostasis, Neuroendocrine Function and Metabolism"
- Proceedings of the National Academy of Sciences of the United States of America: "High Salt Intake Causes Leptin Resistance and Obesity in Mice by Stimulating Endogenous Fructose Production and Metabolism"
- Obesity Reviews: "Leptin Resistance in Diet-Induced Obesity: The Role of Hypothalamic Inflammation"
- Hormone Health Network: "What Is Leptin?"
- University of Rochester Medical Center: "Leptin (Blood)"
- Hormone Health Network: "Ghrelin"
- Centers for Disease Control and Prevention: "How Much Sleep Do I Need?"
- National Sleep Foundation: "The Connection Between Sleep and Overeating"
- African Health Sciences: "Impact of Moderate Versus Mild Aerobic Exercise Training on Inflammatory Cytokines in Obese Type 2 Diabetic Patients: A Randomized Clinical Trial"
- Medical Sciences: "Exercise Increases Adiponectin and Reduces Leptin Levels in Prediabetic and Diabetic Individuals: Systematic Review and Meta-Analysis of Randomized Controlled Trials"
- Journal of Young Pharmacists: "Changes in Leptin in Relation to Increased Testosterone Levels Associated With Eurycoma Longifolia Jack (Tongkat Ali) Root Extract Consumption in Male Rats"
- International Journal of Obesity: "Symptomatic Response to Testosterone Treatment in Dieting Obese Men With Low Testosterone Levels in a Randomized, Placebo-Controlled Clinical Trial"
- Advances in Nutrition: "Dietary Components in the Development of Leptin Resistance"
- American Journal of Physiology: "Selective Leptin Resistance Revisited"
- AYRA Atherosclerosis: "Dietary Intakes and Leptin Concentrations"
- Current Opinion in Endocrinology, Diabetes, and Obesity: "Testosterone and Weight Loss: The Evidence"
- Cell Metabolism: "Defining Clinical Leptin Resistance - Challenges and Opportunities"
- Nutrition Journal: "The Relationship Between the Leptin/Ghrelin Ratio and Meals With Various Macronutrient Contents in Men With Different Nutritional Status: A Randomized Crossover Study"
- Today's Dietitian: "Appetite Hormones"