When we talk about weight loss or gain, we often talk about the things outside that impact our bodies. Cardio, resistance training, diet, and even sleep all come to mind. These are important, but there are powerful things going on inside your own body that affect your weight.
Your body produces two hormones — called ghrelin and leptin — that help control your appetite and manage your metabolism. They can make a big impact on your hunger levels, and learning how to manage them is so helpful.
Ghrelin is a hormone that is produced in your gut, specifically in the stomach and small intestine. It travels from your gut through your bloodstream into your brain, where it has many different functions.
However, the biggest role it has is telling your body to be hungry. Ghrelin sends signals to your body to increase its appetite, so you start to want to eat more food. Because of this, ghrelin has been nicknamed the “hunger hormone.”
The higher your levels of ghrelin, the hungrier you will feel. In animal studies, rats injected with the hormone rapidly gained weight. And when researchers gave the hormone artificially to people, the participants ended up eating 30% more than they did before.
Ghrelin also helps to manage your sleep cycle, carbohydrate metabolism, your reward-seeking behaviour, and taste.
Like Ghrelin, leptin is a hormone that helps manage your appetite. But, unlike ghrelin, it doesn’t tell your body to eat more. Instead, it tells your body that you have enough fat stored up. Leptin helps you feel full, and it lets your body know that it doesn’t need to keep eating.
When your fat cells produce less leptin, your body knows to eat more to keep from starving. But, when you have lots of leptin, your body doesn’t feel the need to eat. Because of this, it is sometimes called the “starvation hormone,” although some like to refer to it as the “obesity hormone” or the “fat hormone” instead.
Leptin is made in your fat cells. From there, it travels to your brain through your bloodstream. By helping your body regulate its appetite, leptin is really helping you manage your long-term energy and metabolism.
Leptin also impacts fertility, the immune system, and brain function.
Your ghrelin level will rise and fall throughout the day in response to when and what you’ve eaten. Right before a meal, when your stomach is empty, your ghrelin levels will be pretty high. Your body is telling you that it is time to eat! Similarly, ghrelin levels lower after you eat, and you no longer feel as hungry.
Ghrelin levels also increase when you start a diet. After all, your body is trying to protect you from starving! In one study, researchers found that people had almost a 25% increase in ghrelin levels during a six-month-long diet. Other, more extreme diets caused even higher increases.
The increase in ghrelin when dieting happens to most people regardless of their weight or body fat percentage, and your ghrelin levels seem to increase more and more the longer you diet. These hunger signals can make the dieting process more challenging, and deter your weight loss progress.
Scientists are still trying to understand the relationship between obesity and ghrelin. Some studies suggest that people who are obese might have higher levels of ghrelin due to overly active ghrelin receptors, but other studies indicate that people who are obese might simply be more sensitive to the hormone.
Your leptin levels increase when you eat. Your body fat has increased, and your fat cells are letting you know that you don’t need to eat more. This helps you eat less and burn more fat. The opposite is also true. When you eat less, your body fat goes down, and your leptin levels follow.
Sometimes, your brain doesn’t respond to your hormones correctly. When this happens with the hormone leptin, it is called leptin resistance.
When your body is resistant to leptin, your brain doesn’t tell your body to burn through stored fat for energy, and your fat cells build up. Because of this, people who have leptin resistance are prone to weight gain, obesity, an increased appetite, and other health conditions.
Leptin resistance often occurs in people who are already obese or who struggle with weight management, which is why leptin is sometimes called the “obesity hormone.” People who are obese have a lot of fat in their fat cells, and fat cells produce leptin in proportion to their size. As a result, people who are obese have high levels of leptin that should be telling the body to burn fat and reduce hunger.
However, for many people, this doesn’t occur. Instead, the brain doesn’t see the leptin. It thinks that you’re starving, and it encourages your body to get more body fat. It does this by:
Leptin resistance might be one of the biggest reasons diets fail for some people, and it can cause a lot of back-and-forth weight loss and weight gain. This is what the cycle looks like for many people:
Various factors can play a role in causing leptin resistance.
Inflammation throughout the body seems to be one of the biggest causes of leptin resistance. One way to tell if you have inflammation is to pay attention to your PMS symptoms. If you struggle with bad cramps, sore breasts, and cravings, you likely have inflammation.
Several things contribute to inflammation and to leptin resistance, including:
I’ve struggled with poor gut health in the past, and it can be so frustrating to manage. Having poor gut health means that you’ll crave more food (and often eat more as a result) and your gut will struggle to digest nutrients properly.
Gut health is a complex topic, and you can read more about my experiences with it. However, if you struggle with your gut health and you suspect you are leptin resistant, you should make sure to avoid ultra-processed foods. These foods will further hurt your gut and raise your inflammation levels.
Researchers are still working to understand the exact role ghrelin and leptin play when it comes to weight loss.
However, research does indicate that women with lower levels of leptin at the end of a diet were more likely to stay on a healthy diet. Women also seem to be more influenced by leptin levels than men are.
Learning how to regulate your hormones through your own lifestyle decisions can help you feel better, lose weight, and have more energy.
Exercise helps you boost your metabolism and increases your lean muscle mass. It also makes your body more responsive to leptin. Regular exercise will help your body balance its hormones, and it will also help you de-stress.
However, be careful not to over-exercise. Give yourself days off, especially if you’re feeling burnt out. Too much exercise (typically over an hour a day on a regular basis) can actually lower your leptin levels and make you hungrier.
Getting enough sleep (typically about 7-9 hours for adults) will help your body manage its hormone production and will reduce inflammation.
Sleep also helps reduce levels of the stress hormone, cortisol, which is associated with overeating and weight gain.
Try to limit foods that cause inflammation, including sugar, simple carbs, and trans fats. Sweets, soda, and ultra-processed foods are bad for you in general, especially if you want to better manage your hormones.
If you notice that other foods (like gluten or dairy) cause you inflammation, consider limiting those foods too.
Triglycerides are a type of fat lipid that your body uses as energy in-between meals. High levels of triglycerides can stop leptin from being able to travel through your blood to your brain. Sweets and other simple carbohydrates can increase the levels of triglycerides in your body.
However, these foods are great at lowering triglycerides:
I’m a big fan of helping girls eat healthy for the long-term. Although some people find success from diets, I don’t support extreme diets that overly restrict calorie levels because these diets are rarely sustainable and they damage your overall health. Many people fall off of them, end up binging, or just don’t feel good.
But overly restricting your calories might end up hurting your weight loss goals too. If you’re not eating enough, your ghrelin levels will increase. You’ll end up feeling even hungrier, and your body will think it needs to try to gain weight.
You should be eating enough healthy food to sustain you throughout your day. If you need help knowing roughly how many calories to eat, you can learn more here.
What you eat matters too, especially if you are trying to lose weight and are eating at a slight calorie deficit. Make sure that you’re eating fiber and protein, as both these will help you feel fuller and more satisfied after eating. Eating protein at every meal, especially breakfast, can also help reduce ghrelin levels.
These are some other foods that can help lower ghrelin levels:
Try to avoid processed sugar and high-fructose corn syrup. These can prevent your body from responding to ghrelin signals after meals.
Gut health and leptin resistance are related, and gut health and ghrelin levels are too. Prebiotics will also help you feel more full and satisfied after eating. Some of my favorite prebiotic foods include:
I also suggest that you take a probiotic supplement.
Ghrelin and leptin are powerful hormones that play incredible roles in keeping us eating properly. Unfortunately, if your body doesn’t respond correctly to the signals these hormones give, you can experience unwanted weight gain and other symptoms.
Let me know if you have any questions about managing ghrelin and leptin. :)
Love Rachael Xx