The Hunger Hormone, Ghrelin

We know that as leptin decreases (it is inevitable over the course of a diet), you start to lose your ability to feel full. As that is happening, ghrelin is increasing, which is telling you that you are hungry. You can see how this is a recipe for disaster over the course of a period of caloric restriction. Satiety down, hunger up. Let the struggle to adhere commence.

What exactly is ghrelin? Ghrelin is the gastrointestinal peptide hormone that acts in the brain to regulate food intake, body weight adiposity, and glucose metabolism. (3,4) Ghrelin is orexigenic (appetite-stimulating), but it does not only play a role in our hunger/fullness cues. Ghrelin also inhibits insulin secretion, increases intestinal motility, and decreases thermogenesis among many of its other functions. (3,4) For the purpose of this article, however, we will be looking at how it specifically impacts our hunger. 

How does ghrelin act? Ghrelin stimulates the activity of neurons expressing neuropeptide Y (NPY), AgR and orexin. (2) I am going to focus on NPY. NPY is a small protein which, in research done on mice, has been shown to cause massive overeating. To date, NPY neurons are the most powerful drivers of eating known to science. (1) NPY neurons are produced endogenously by the VMN satiety center (which was discussed in last week’s article on leptin) and research has shown that the amount becomes more abundant after fasting, which further suggests that it is triggered by feelings of hunger. These feelings can develop if the body feels threatened by a state of starvation, such as during a dieting phase. (1) Because ghrelin stimulates the activity of these neurons that command you to eat, it is crucial that we keep ghrelin as well as leptin levels in check if we want to have a well-regulated appetite.  

So, how is ghrelin physiologically correlated to leptin? When leptin is present in adequate amounts, it reduces NPY levels in the brain and thus aids in controlling food intake. When leptin levels decrease, however, neurons that drive eating turn on and neurons that inhibit eating turn off, increasing the drive to eat. (1) This is all in an effort to bring the body back to the weight that it wants to be at (like last week, think “set-point”). Eating motivates us in two ways that reinforce each other. First, unpleasant hunger neurons get turned off (leptin declines), followed by food reward neurons get turned on (ghrelin rises). (1) Your body is in a constant state of trying to maintain homeostasis, it does not care about having a 6-pack and it does not care about its adaptations/mechanisms to restore homeostasis make you uncomfortable. For that reason, it is imperative that dieting is done strategically and with long-term health in mind. 

How can we attenuate the increase of ghrelin during a period of caloric restriction in order to increase our chances of adhering to our plan over an extended timeframe? First and foremost, all of the protocol listed in last week’s newsletter on leptin need to be taken into consideration and implemented, as we now know that as leptin decreases, neurons such as NPY levels increase thus driving us to eat. Next, we can look at some simple implements to fight off hunger:

  1. Eat voluminous foods. Fill your plate with non-starchy vegetables as the fiber content will help create a feeling of fullness without excess calories. 

  2. Drink plenty of water. Staying hydrated consistently throughout the day is another great way to increase the feeling of fullness.

  3. Honor your hunger signals. If you start to feel hungry, eat something. Even if you are in a pretty severe restriction period (say for a bodybuilding show), you can typically squeeze in some raw vegetables. 

  4. Take time to decipher between true hunger and emotional hunger. Often times we convince ourselves we are hungry when in fact we are trying to procrastinate doing something, we are bored, or because we are stressed out. If you think your hunger is coming from a place of boredom or stress, I encourage you to step away from the kitchen for 30 minutes to either take a walk, run an errand, or do a task. If at the end of those 30 minutes you are still hungry, then by all means eat. However, I find that often times people will notice that by removing themselves from the food, they are not actually hungry.

We have now taken a look at two opposing hormones that make adhering to dieting protocol incredibly challenging. With a deeper understanding of the roles of leptin and ghrelin in the body, we may be able to utilize the simple, yet smart protocol that has been laid out over the past two weeks to either minimize their effects or prolong the time with which they show up in the dieting phase.

As always, if you need help on your journey – apply for coaching with Team LoCoFit!