Weight loss is a topic that interests most people. I'm not exaggerating - around 70% of adults in the US are overweight or obese (source). As someone who lost 100 pounds in the last few years, I'm intimately familiar with this struggle.
I was told over and over again that it's a matter of simply eating less and moving more. I felt ashamed that I was finding something so supposedly "easy" almost impossible.
Maybe some people have iron willpower, but that's not me. Even with big meals and snacks in between, I was nearly always hungry. Resisting cravings is hard! And when I gave in during moments of weakness, the feeling of failure lead to emotional binge eating. It was a vicious cycle.
When I learned about leptin, it all started to make sense. For most overweight and obese people, leptin plays a big role in the behaviours surrounding weight loss and explains why it's so darn tricky. I'm not saying our weight is out of our control - we're not slaves to our hormones. In fact, the opposite is true.
Learning how leptin works, and how to use it to your advantage, can unlock the key to achieving and maintaining a healthy weight. Read on to find out more.
What is Leptin?
Leptin is a hormone produced by the fat cells in our bodies. It was named after the Greek word "lepto", meaning "thin" (source). Leptin is involved in many vital bodily functions, however the one we are most interested in today is promotion of satiety.
Satiety is a feeling of fullness created by our brains. In a nutshell, leptin makes it easier for us to eat less. It's also part of the reward system. When leptin levels are low, food seems very rewarding. High leptin dampens the reward system so that high calorie food just doesn't look as good. This means we have a better chance at resisting temptation. (source)
In addition, leptin increases nervous system activity, which stimulates fatty tissue to burn energy. So, in theory, when we have eaten enough and have a lot of fat cells producing leptin, this hormone tells our body to use our existing fat for fuel rather than taking in more food. (source)
Hormone Balance and Appetite
Leptin isn't the only hormone involved in appetite, metabolism and weight control, although it's often considered the most important. Other important players are ghrelin and amylin.
Ghrelin does the opposite to leptin - it increases your appetite. It's produced in your stomach and sends signals to the brain in a similar way to leptin. Ghrelin levels increase when you're starving and are lowered for about three hours after a meal. It should be apparent that leptin's job is to counteract ghrelin. (source)
Amylin works with leptin in promoting satiety, in fact, leptin triggers amylin release. Amylin slows gastric emptying - i.e. it keeps food in your stomach for longer. This has two effects, firstly, it slows movement of glucose, preventing blood sugar spikes. Secondly, if your stomach remains full for longer, you're less likely to consume more food. (source)
A study gave leptin and amylin to obese rats. The result was sustained weight loss. There is some interest in amylin as a possible therapy for obesity.
With all these chemicals flying around our bodies, it's easy to feel like our eating is out of our hands. Don't worry, I'm going to share some simple tools which can help make hormones work for you rather than against you. First let's examine leptin's precise role in obesity and weight gain.
The Link Between Leptin and Obesity - Leptin Resistance
If you've been paying attention so far, you should understand that the human body has plenty of complex mechanisms for ensuring we don't eat too much - or too little. So why is obesity even a problem?
On the surface, it doesn't make sense. It's well established that low leptin levels cause uncontrolled hunger and weight gain. However, low leptin isn't the issue for overweight people.The more fat cells we have, the more leptin they produce.
This should send screaming signals to our brain to put the fork down. This is what scientists thought initially, but when they conducted studies, they were in for a surprise.
Research scientists use a strain of mouse called "Ob" as a model of obesity. The Ob mouse has a genetic mutation which makes it obese and unhealthy.
The Ob mouse produces no leptin at all. When scientists gave it leptin it became "thin, vibrant, and very healthy within weeks". It seemed that this would be a cure for obesity. Unfortunately, these rodent results didn't carry through to humans.
Unlike the Ob mouse, obese humans don't have a shortage of leptin. In fact, almost all overweight and obese people have excess leptin. Giving extra leptin didn't have any effect. (source)
The reality is that prolonged exposure to leptin makes your brain resistant to the "full" signals. The exact mechanism isn't certain but it's thought that somewhere along the leptin communication chain, a type of signal receptor becomes overloaded and simply stops working.
The result is a brain which feels starving no matter how much you eat.
This is bad news. "Chronically high leptin levels are linked to obesity, overeating, and inflammation-related diseases, including hypertension, metabolic syndrome, and cardiovascular disease." (source)
Why Do We Become Resistant to Leptin?
Why does all of this happen? Well, it's theorised that our bodies evolved to adapt to food shortages of prehistoric times rather than the world of plenty we have in developed countries today. The main role of leptin was most to act as a starvation signal and maintain fat stores for survival not as a satiety signal to prevent overeating.
Another theory is that the leptin in the blood cannot enter the brain in overweight individuals. High levels of triglycerides may prevent the hormone passing through the "blood brain barrier".
A third suggested mechanism involves high fructose and high fat diets. This has been shown in rat studies. The average US diet unfortunately contains a lot of fructose. The best way to curtail it is to eat whole foods and avoid everything processed.
Leptin and Weight Loss
Now that you understand the basics of leptin and leptin resistance, it's easy to see how this hormone can be a huge help or hindrance in weight control. While the old adage of "calories in, calories out" still stands, our failure to stick to a calorie deficit isn't a sign of character weakness, but rather the odds are most stacked against us due to hormonal issues.
Dr Rosedale describes it beautifully when he says "hunger is a very powerful, ancient, and deep-seated drive that, if stimulated long enough, will make you eat and store more energy. Asking somebody to not eat, to voluntarily restrict calories even though they are hungry, is asking the near impossible.
The only way to eat less in the long-term is to not be hungry, and the only way to do this is to control the hormones that regulate hunger, the primary one being leptin."
So, how do we control these hormones for weight loss? It's actually pretty easy. You don't need any special supplements (those don't even work, I'll explain why later). All you've got to do is adjust your diet and make some healthy lifestyle changes.
1. Avoid Crash Diets
Drastically reducing your calorie intake guarantees weight loss. It's just plain old physics - if we don't consume enough food, our bodies are forced to burn fat for energy. While in theory, ridiculous weight loss plans such as "the cabbage soup diet" should work, in reality, they don't produce sustained results for the majority of people.
Apart from the fact that these weird diets are lacking in tons of nutrients, fasting or following a very low calorie meal plan will lower your leptin levels. This means hunger pangs and cravings will kick into overdrive and make it nearly impossible to resist a binge.
To keep your leptin levels stable, try a more moderate diet. A deficit of around 500 calories a day will result in a loss of 1 pound per week for most people. It may be a test of your patience but you're more likely to succeed at reaching your goals in the long run.
2. Cut Out High Fat and High Carbohydrate Meals
As we already mentioned, a diet high in processed carbohydrates and fats will increase leptin resistance. One study compared this type of diet with an American Heart Association-recommended meal rich in fiber and fruit. I'm sure you can guess which one came out on top? If you guessed the fruit and fiber meal, you're correct.
Another benefit to reducing carbs and fat in your diet is that it will lower your triglyceride levels. Triglycerides block leptin transport into your brain, meaning you don't get those vital "full" signals. (source) Getting your triglycerides down also reduces your risk of heart disease so it's a good idea whatever your weight.
3. Increase Protein
Now you know what you shouldn't be eating, what is recommended? One key nutrient is protein. Not only does filling up on protein make it easier to leave out fat and carbs, but it increases leptin sensitivity and aids weight loss. (source)
4. Have Healthy Sleep Patterns
Leptin is entwined with our lifestyles in other areas than just diet. Sleep plays a major part. If you don't get enough sleep, it actually makes you feel hungry! This is because blood levels of leptin decrease with sleep deprivation.
On the flipside "restful sleep, i.e., 8 to 12 hours of unbroken sleep, can increase leptin to normal levels." (source) If you want some tips on how to achieve this, check out my article on improving your sleep environment.
Another lifestyle factor influencing leptin levels is how much exercise you get. You may think you've got an excuse to stay on the couch if you heard that exercise lowers leptin levels. This is true for healthy-weight people. It makes sense because you need to eat more to fuel your activity.
However if you are carrying extra weight and have leptin resistance, physical activity can help reverse this. (source) It's certainly extra-motivating to know that it's not just the calories you burn on the treadmill that will help you drop pounds, you're also healing your hormone receptors by exercising.
Check our top 5 hand exercise right here!
Leptin and Weight Loss Maintenance
If you've managed to lose some weight already, you still need to pay attention to leptin. It's an unfortunate truth that many dieters regain weight lost within a few months or years - sometimes ending up heavier than they started.
Especially if you started out obese or very overweight, your leptin levels will drop simply because your fat cells are still there - but they've shrunk. People who have always been thin have fewer fat cells, whereas those who were heavy and then lost weight have more fat cells but the cells become smaller.
"The result is that a person who has lost weight below their natural body fat set-point has a lower basal metabolic rate than an individual at the same weight who is of that natural weight; these changes are leptin-mediated, homeostatic responses meant to reduce energy expenditure and promote weight regain as a result of fat cells being shrunken below normal size" (source).
This doesn't mean that you're doomed to gain weight back. Personally I have kept my weight stable for over 5 years. However it does mean that you will have to put in a bit more work than those who were never overweight. Stick to my 5 tips above and you will be well on your way to maintaining a healthy weight.
Do Leptin Supplements Work?
If you've been looking into leptin and weight loss at all online you've probably come across some leptin supplements. Now that you understand the concept of leptin resistance, you probably see why they don't work.
A leptin resistant person can take in as much leptin as they like (theoretically) but their brain will never receive those "full" signals. Not only that, but leptin is a protein the same as any other in our diet (meat, fish, legumes…). When taken orally we will simply digest it. There is no chance of it reaching our brain at all.
Metreleptin (Myalept) is a synthetic version of leptin which is used for treating diabetes and dyslipidemia. It has no effect on and is not licenced for weight loss.
Final Thoughts on Leptin and Weight Loss
I hope that this article has helped shine some light on the topic of leptin and weight loss. It certainly gave me some hope to learn that I could make my hormones work with me rather than against me in my weight loss journey. Five easy ways to increase leptin and stop hunger include:
- Avoid crash diets
- Cut out high fat and carb meals
- Increase protein in your diet
- Get enough sleep
If you have any questions or experiences with leptin and weight loss, please leave me a comment, I'd love to hear from you.