As research uncovers more about the relationship between the gut, brain, and overall health, the term “hunger hormones” is becoming more common. It shows up in the world of weight management, nutrition, hormonal health, and endocrinology – even as a topic on social media as amateurs and experts explore the connectivity of the gut-brain axis.
What are “hunger hormones”?
Hormones are chemicals that essentially tell the body what to do and when to do it. They do this by carrying messages via the blood to the brain, muscles, and other organs. When you think of hormones you probably think of the common ones such as estrogen, testosterone, insulin, and thyroid to name a few; however, research has discovered more than 50 hormones in the human body originating from many different places including the brain, kidneys, ovaries, and testes. Hormones are essential to life in that they help maintain homeostasis, or the body’s internal balance.
Hormones carry messages to help regulate metabolism, and are intricately connected to appetite. There are two main hormones that drive hunger: leptin and ghrelin.
The Role of Leptin
The role of leptin is to suppress food intake. (An easy memory trick is to think of leptin / “lighten”, or to lighten the body weight of an individual). Leptin is released by adipocytes, which are fatty tissue cells found all over the human body. Once leptin is secreted by adipocytes it travels through the blood, passes the blood brain barrier, and is received by the hypothalamus – which is the part of the brain that helps maintain the body’s homeostasis. Once the hypothalamus receives the signal from leptin, it tells the body to cut down on appetite and cravings. High levels of leptin tell the body not to eat, and low levels of leptin trigger feelings of hunger.
So does increasing leptin levels suppress hunger? Not quite. If too much leptin is secreted throughout the body, then the receptors on the hypothalamus become resistant and the brain is no longer issuing the correct hungry / full signals. Because leptin is secreted by fatty tissue, the amount of leptin an individual has is directly correlated to percent body fat – meaning the more fatty tissue, the more leptin, and the higher risk of leptin resistance. So, even if the body is producing the hormone that says “don’t eat”, the brain is not able to read that signal. A balanced leptin hormone is critical for success with weight management, however increased body weight can lead to a leptin imbalance and resistance.
Improving Leptin Sensitivity
Fortunately, there are ways to improve the leptin balance and increase leptin sensitivity. Reducing triglycerides, exercise, getting appropriate sleep, and including protein with meals and snacks can help.
| 4 Ways to Increase Leptin Sensitivity: | ||
| What to do | Why We do it | Examples |
| Reduce triglycerides | Triglycerides prevent leptin receptors from receiving leptin signaling. | Decrease the amount of processed foods in your diet such as sodas, fruit juices, packaged, bagged, or boxed foods. While grocery shopping, try and limit your shopping items from the middle aisles and stay on the periphery where fresh produce, meats, dairy are located. |
| Exercise | Exercise makes us more susceptible to leptin. | Try completing some of your workouts first thing in the morning. |
| Get your sleep | Leptin sensitivity improves with quality, restorative sleep. | Get a minimum of 7 hours of sleep nightly. |
| Eat protein | Amino acids (the building blocks of protein) make leptin receptors more sensitive. | Incorporate lean protein at every meal such as white meat poultry, fish, lean beef, beans, lentils, or tofu. |
The Role of Ghrelin
Ghrelin is a partner hormone to leptin in regulating appetite (think “growl” because increased ghrelin means the stomach is probably growling!) The gut makes ghrelin when the stomach is empty and in fact, over 90 percent of the body’s ghrelin is derived from the stomach and a part of the small intestine called the duodenum. Ghrelin moves through the bloodstream, passses the blood brain barrier, and attaches to the reward part of the brain, the hypothalamus – the same structure involved in receiving signals from leptin – and the spoke of the connected gut-brain axis. The hypothalamus receives the message from ghrelin, tells your brain that you are energy deficient, and signals the body to eat with a “growling” of the stomach. Eating stretches the stomach, which signals the stomach to stop producing ghrelin.
Ghrelin comes in waves, increasing sharply before a meal and falling abruptly after a meal. But, it takes about 10-15 minutes before the brain recognizes that the stomach has stopped producing ghrelin. This delay can cause overeating, which is why it is important to eat slowly. Ghrelin fluctuates from meal to meal and is also known to be elevated later in the night around 9 or 10 pm – driving the “night time munchies”.
Restoring Ghrelin Balance
Healthy habits, such as adequate sleep, eating vegetables, reducing stress, and eating slower can help keep ghrelin levels in balance.
| 3 Ways to Keep Ghrelin Balanced | ||
| What to do | Why We do it | Examples |
| Get a minimum of 7 hours of sleep. | Lack of sleep can increase levels of ghrelin (and decrease leptin levels). This leads to increased hunger and appetite, ultimately causing overeating. | A good sleep hygiene tip is setting your alarm for the same wake up time each morning. If you go to bed earlier or later in the evening it’s easier to monitor the impact on appetite the next day. |
| Eat more veggies | Increase vegetable intake at meals. Vegetables are mostly water, which fill / stretch the stomach sooner than most foods, ultimately, signaling your brain that you are fuller sooner. | Try filling half of your lunch and dinner plate with coniferous vegetables such as roasted broccoli and cauliflower, a spinach salad or cooked cabbage. |
| Control stress | Stressful situations cause ghrelin to be released. | Try to weave in a variety of anti-stress techniques into your day-to-day with exercise, journaling, spending time outdoors, sustaining positive relationships, getting enough rest, meditation, prayer, and downtime. |
| Eat slowly | Because it takes 10-15 minutes before your brain recognizes that the stomach has stopped producing ghrelin and that you are full. | Take a few seconds between each bite. Give your stomach the time to expand and send the signal to your brain that you have eaten enough. |
Hormones and Metabolism
In summary, it is essential that leptin and ghrelin are balanced to support healthy weight maintenance. When body fat is high, leptin is high, which can lead to leptin resistance – or the brain being unable to process hungry / full signals. Similarly, excess body weight causes ghrelin levels to be low – meaning the body may not feel hungry even though it has not eaten. Together, this metabolic distortion makes it incredibly difficult for individuals with excess body weight to accurately interpret or manage their appetites, leading to over- or under-eating and challenges with weight loss.
The solution is to decrease the amount of body fat, through careful and appropriate dietary changes, increased exercise, and other evidence-based recommendations – including anti-obesity medications.
The human body is incredibly intelligent. It knows how much energy is needed to function at its best. With appropriate lifestyle habits and support from healthcare professionals who understand the complex nature of obesity and excess body weight, metabolic balance can be restored and individuals can achieve healthy weight loss.
Citation:
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- ATP Science. “Episode 228 – Leptin and Ghrelin – Understanding appetite.” ATP Science, atpscience.com/podcasts/episode-228-leptin-and-ghrelin-understanding-appetite/. May 24, 2022.
- Attia, Peter. “Finding the Obesity Gene and Discovering Leptin.” peterattiamd.com/rudyleibel/. May 22, 2022.
- Mantzoros, Christos, et al. UpToDate, 30 Apr. 2021, www.uptodate.com/contents/physiology-of-leptin?search=leptin&source=search_result&selectedTitle=1~98&usage_type=default&display_rank=1#references.
- Cabral, Stephen. “Rebalance Your Hormones.” The Cabral Concept, https://stephencabral.com/podcast/404.
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- Liddle, Rodger A, et al. UpToDate, 27 Apr. 2021, www.uptodate.com/contents/ghrelin?search=ghrelin&source=search_result&selectedTitle=1~42&usage_type=default&display_rank=1.
- Suni , Eric, and John DeBanto. “Can Overeating Cause Sleep Disturbances?” Sleep Foundation, OneCare Media Company , 19 Apr. 2022, www.sleepfoundation.org/physical-health/sleep-and-overeating.
- Levy, Jillian. “Ghrelin: How to Control This Hunger Hormone to Lose Fat.” Dr. Axe, 12 Mar. 2022, draxe.com/health/ghrelin/.
