Know Your Hunger Hormones

Health Writer

Why do I feel hungry all the time?

Why do I still feel hungry after I eat?

Am I truly hungry, or is something causing me to just feel that way?

Am I actually thirsty, and why can’t I distinguish between hunger and thirst?

Why is it so hard to lose weight and keep it off?

If you struggle with obesity, if you chronically diet, or if you feel like you were born to eat, then it’s important to understand the reasons why you have more than just a healthy appetite. There are many different elements at play that guide hunger and satiation. Gut microbe balance, habitual emotional eating, chronic consumption of highly caloric and processed foods can all drive appetite and perpetuate hunger.

Many dieters struggle to maintain weight loss. Until recently, eating less and resisting temptation was largely considered an issue of willpower. With obesity now categorized as a disease, and much more research being done on the causes of obesity, there is now a better understanding of the gut and brain hormones that guide hunger and satiation. Two hormones in particular have been identified as fundamental to appetite: leptin and ghrelin.

Leptin: The 'feel full' hormone

Leptin was discovered in 1994, and after being produced by fat cells works to suppress appetite at the brain level. Think of it as “the stop” hormone. Fat is not an inert storage deposit but rather an actual endocrine organ that can produce hormones. Leptin is just one hormone produced by fat cells. How much leptin a person has circulating depends on the amount of fat a person carries. So it would seem intuitive to assume that larger people who are obese would have “loads of leptin” and be satisfied easily, but the contrary is actually true. People who are diagnosed with obesity and have very large fat stores typically develop leptin resistance. This means that leptin receptors do not bind the available leptin efficiently so the brain does not receive the signal of fullness.

As a result, someone with obesity feels hungrier compared to a person who responds to leptin and, secondly, metabolic rate slows due to leptin’s inefficiency. Similar to insulin resistance, which is associated with higher levels of inflammation in the body, leptin resistance also appears to be mediated by inflammation. Fat cells, especially those in the abdomen or gut, produce inflammatory substances which block leptin’s effect. That’s why some experts recommend eating a diet rich in anti-inflammatory foods (containing omega-3 fatty acids and antioxidants) in order to improve leptin resistance. More research is needed to see if this recommendation is validated by science.

Ghrelin: Driver of hunger

Ghrelin has been called the primary driver of hunger, a powerful hormone that stimulates appetite. Think of it as “the go” hormone. Ghrelin is mostly secreted by cells in the lining of the stomach. It travels through the blood to the brain, initiating the signal to eat. Ghrelin works on a cyclical basis, rising to almost two-fold levels to stimulate hunger and the desire to eat food, and then falling to lower levels after food is consumed. Levels are usually lowest one hour after finishing your meal. This cycling normally occurs every four hours. This is one of the reasons that it seems to make sense to set feedings including breakfast, lunch, dinner and one or two snacks, with four hour intervals in mind. Once you go to sleep, ghrelin levels will rise so that you’re pretty hungry for breakfast.

It’s important to heed ghrelin and hunger because it will continue to rise until you eat. It’s conceivable that if your meal was full of sugar and devoid of fiber, then low blood sugar levels and the inflammatory nature of the meal may instigate hunger for your next meal sooner than the normal cycle -- but that's just a theory.

When it comes to individuals diagnosed with obesity, there is a malfunction of the ghrelin system. Ghrelin levels tend to run lower in these individuals, but they are also more sensitive to these lower levels of the appetite-stimulating hormone. There is one obesity disorder, Pader-Willi Syndrome, in which ghrelin levels run very high, which drives these individuals to eat excessively and constantly.

Next Up: "Know Your Hunger Hormones Part 2: Other Hunger Hormones and Tips to Balance Them"

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