Leptin and ghrelin are the two key hunger hormones that affect how much fat you store, how hungry you are and ultimately shape your entire physique and levels of body fat.
Despite the fact that lowering calories and regular exercise is the number one way to change your body weight and composition, the hormones leptin and ghrelin arguably play an equally important role when it comes to gaining, losing or even maintaining weight.
In this article, I’ll give a brief rundown of what these two hormones are, how they are regulated and store body fat, why they are key in weight regain after a diet and how you can optimize them for success.
Leptin Regulates More Than Just Food Intake
In general, Leptin is known as the ‘good’ hunger hormone with ghrelin being the ‘bad’ hormone.
Secreted from body fat tissue, leptin is a hormone that acts on the brain to regulate how much food we should eat, and how our body metabolizes it once we do (i.e. stores it as fat) (1).
You see, our body is actually quite intuitive in the sense that it has many regulatory processes in place to ensure survival. Dating back to when we were cavemen, our body has been designed to tell us when to eat and store body fat for survival. Leptin is no different and so plays a key role in this survival mechanism.
Leptin is largely regulated by how much body fat you have, since that’s the area that it actually comes from and where it is produced. When body fat levels rise, leptin is supposed to act on the brain to reduce food intake and actually help keep you lean, hence it being known as the good hunger hormone.
When leptin is released, it is secreted into the blood, whereby it travels to a region of the brain called the hypothalamus. There then begins a cascade of events that is meant to reduce food intake (2).
When body fat is high (in overweight or obese individuals), there is less of a need for the body to be in “survival mode”.
This causes an increase in leptin which helps reduce food intake and an increase in energy expenditure or metabolic rate to basically burn fat (remember, weight loss is basically a reduction in calorie consumption and an increase in calories burnt).
Even more interesting, as body weight and fat begin to decrease, leptin levels begin to decrease as well. This is a mechanism put in place by the body to ensure that body fat levels remain fairly constant since survival is paramount (remember our body doesn’t know we want six pack abs, it actually senses this as dangerous for survival) (1).
Chances are, you’ve experienced this increase in leptin if you’ve ever hit a plateau with weight loss. Realistically, your body doesn’t want you to be too overweight, but it equally doesn’t necessarily want you to be super lean either.
Ghrelin Is A Major Regulator (Cause) Of Hunger
While leptin encourages you to eat less food, ghrelin does quite the opposite.
Ghrelin is a hormone that is secreted by cells within the stomach that increase appetite and feelings of hunger.
Just as leptin is in place to ensure your survival, ghrelin acts in a similar way to ensure that you’re not starving yourself. This hormone is not only regulated by your current state, but also by how much food is in your stomach and when you normally eat.
Interestingly the cells that secrete ghrelin are actually sensitive to stretch, which is why I always recommend low calorie dense foods to reduce hunger. When your stomach is empty, the cells are not stretched, which causes them to secrete the ghrelin hormone (3).
This hormone is then sent to the same section of the brain, (the hypothalamus), in which leptin acts which causes different events to encourage hunger and food consumption.
Further, once food is ingested and these cells become stretched, there is a decrease in both the secretion and action of ghrelin on the brain, triggering a reduction in feelings of hunger and thus food intake (3).
In addition to these cells being sensitive to touch, they are also sensitive to time.
Just as your body has a circadian rhythm or a sleep wake cycle, so the cells which secrete ghrelin actually act in a similar manner. Cells called oxyntic cells act on a rhythm of when you normally eat and normally don’t eat.
According to your specific schedule, these cells are actually programmed to secrete ghrelin prior to the time when you normally consume foods. This is why you are often hungry at breakfast, lunch and dinner (4). Interestingly, this can also change over time, which is why people who do not normally eat breakfast are fine skipping it as their body gets used to it.
This secretion of ghrelin at normal times is to ensure that you consume food at regular intervals and maintain survival.
The big problem is we are no longer cavemen trying to maintain enough body fat for the cold winters. Sadly, ghrelin doesn’t know this, so, when dieting, ghrelin actually thinks we are starving and works against you, as discussed below.
Weight Loss Attempts Significantly Affect Ghrelin
Despite the fact that many of us want to lose a significant amount of weight, the body often has other plans.
When weight loss attempts are made, this often causes two changes in hunger hormones: a reduction in leptin, meaning that you won’t feel as satisfied and therefore will have the urge to eat more food, and an increase in hunger due to raised ghrelin levels, resulting in the same state of wanting to eat more.
Additionally, ghrelin can tell our body how to store energy (food). When ghrelin shoots up, it may actually have us store more of that food as fat. This, coupled with a decrease in metabolic rate, is why people often struggle to lose weight, even though they are reducing their calorie intake.
All of this combines into the well-known difficulty most of us have losing weight, especially as the diet progresses.
In fact, multiple studies have indicated that with prolonged dieting, ghrelin levels increase significantly. Some studies have shown increases ranging from 24% all the way to almost 41% suggesting that hunger levels significantly increase with calorie restriction (5, 6).
This means once we start dieting (especially after the first 1 to 2 weeks) our hunger will escalate and we may even start storing more fat, as ghrelin has increased.
Being Significantly Overweight Can Cause Leptin Resistance
One of the hallmarks of being significantly overweight is the fact that many of these overweight individuals cannot control their hunger and eating.
Based on the fact that leptin is produced by fat tissue, one would expect that a significantly overweight individual would have high levels of leptin and thus, a reduced food intake and so lose weight.
This is exactly what leptin was designed for. It was basically there to say… STOP, we have enough energy stores (body fat) and we do not need to keep overeating.
Unfortunately, high leptin levels for obese people can cause a disorder called leptin resistance, so this basic human function no longer works efficiently.
Much like insulin resistance, a disorder in which chronically high levels of insulin reduce its effectiveness, the same happens with leptin (7). In other words, after months and years of overeating, leptin will keep getting pumped out but our body becomes resistant to the signals or starts to ignore them.
When this occurs, a large amount of leptin is being produced, but receptors in the brain simply don’t respond to it. It’s an unfortunate and vicious cycle that causes overweight individuals to stay that way due to an inability to control their eating.
In fact, some studies have indicated that leptin resistance may actually be a primary cause of obesity (8).
How To Manage Leptin & Ghrelin
As you can see, modern day obesity and the poor lifestyles that many people lead really mess up the basic functions of leptin and ghrelin, which were originally designed to help us survive as cavemen when there were times of limited food availability.
In summary, when we are dieting ghrelin will spike up, making us constantly hungry, increase cravings and even start to store more fat from the food we do consume.
For obese individuals, the leptin signal will also stop working due to leptin resistance; this means their brain is unable to tell them to stop eating even though they’ve got excessive amounts of stored energy as body fat.
The best way to manage both of these hormones is very simple, and sadly, kinda boring. There’s no magic secret to ‘trick’ these two hormones. Quite simply, the best way to ensure that they stay functioning as intended is to eat a healthy, single ingredient-based diet most of the time, combining it with regular exercise and other healthy lifestyle habits.
Of course, avoiding getting too overweight in the first place can help prevent potential leptin resistance while avoiding drastic and long-term calorie restriction can help reduce the risk of drastic increases in ghrelin secretion.
This is why yo-yo dieting causes so many issues, as all the dieting shoots ghrelin levels sky high, which means when you’ve lost the weight you are still super hungry and just overeat and so regain even more body fat.
As lots of experts are now saying, the best way to avoid these issues is to simply not gain the weight in the first place. Easy to say, I know. However, if you are now stuck with excess body fat you want to lose you must do it in a sensible manner.
Remember, each time you diet you will make leptin/ghrelin levels worse, so be sure to diet in a sustainable manner. Here’s a few extra bonus tips that may help further optimize leptin and ghrelin:
- Supplement with fiber. For example, 20g of Oligofructose (Insulin) was shown to reduce ghrelin levels.
- Eat high protein foods at every meal, which also can help reduce ghrelin levels.
- Eat low energy dense foods such as meats, fruits, yogurts and vegetables which fill your stomach up and can help reduce ghrelin.
- Use calorie cycling to protect your hormones, such as the 90 Day Calorie cycling meals in my 90 Day Bikini plan.
Leptin & Ghrelin Are Key For Weight Loss & Your Goals
Hopefully you can now see how leptin and ghrelin both play an integral role in how the body reacts to weight gain, weight loss and weight maintenance.
Together, these two hormones help to regulate metabolism and food intake to ensure survival. If manipulated properly, you can avoid adverse reactions that may give you a hard time trying to lose body fat or maintain weight loss.
Now you have a basic understanding of how these work you can probably see why it’s so easy to overeat. Additionally, you can maybe see why the stupid yo-yo diet craze just makes it harder for you in the long term, messing up your key hunger hormones.
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- Friedman, J. M., & Halaas, J. L. (1998). Leptin and the regulation of body weight in mammals. Nature, 395(6704), 763-770.
- Ahima, R. S., Saper, C. B., Flier, J. S., & Elmquist, J. K. (2000). Leptin regulation of neuroendocrine systems. Frontiers in neuroendocrinology, 21(3), 263-307.
- Sakata, I., & Sakai, T. (2010). Ghrelin cells in the gastrointestinal tract. International journal of peptides, 2010.
- Lesauter, J., Hoque, N., Weintraub, M., Pfaff, D. W., & Silver, R. (2009). Stomach ghrelin-secreting cells as food-entrainable circadian clocks. Proceedings of the National Academy of Sciences, 106(32), 13582-13587. doi:10.1073/pnas.0906426106
- Cummings, D. E., Purnell, J. Q., Frayo, R. S., Schmidova, K., Wisse, B. E., & Weigle, D. S. (2001). A preprandial rise in plasma ghrelin levels suggests a role in meal initiation in humans. Diabetes, 50(8), 1714-1719.
- Leidy, H. J., Gardner, J. K., Frye, B. R., Snook, M. L., Schuchert, M. K., Richard, E. L., & Williams, N. I. (2004). Circulating ghrelin is sensitive to changes in body weight during a diet and exercise program in normal-weight young women. The journal of clinical endocrinology & metabolism, 89(6), 2659-2664.
- Myers, M. G., Heymsfield, S. B., Haft, C., Kahn, B. B., Laughlin, M., Leibel, R. L., … & Yanovski, J. A. (2012). Challenges and opportunities of defining clinical leptin resistance. Cell metabolism, 15(2), 150-156.
- Jung, C. H., & Kim, M. S. (2013). Molecular mechanisms of central leptin resistance in obesity. Archives of pharmacal research, 36(2), 201-207.