GHRELIN, THE APPETITE GREMLIN
In contrast to leptin, ghrelin acts as an appetite stimulator. It’s released primarily in the stomach, and when elevated, sends a hunger signal to your brain letting you know it’s time to eat. After a meal, you can expect ghrelin levels to return back to baseline within three hours.
Factors like age, gender, BMI, blood glucose levels, insulin levels, leptin levels, and growth hormone (GH) have been shown to affect ghrelin levels. Leptin itself, for example, can help reduce ghrelin.
Furthermore, if you often find yourself feeling full after a tough workout, it could be because of an increase in GH, which can help dampen hunger and food intake by reducing circulating levels of ghrelin.
THE HUNGRY GAMES
Put simply, ghrelin makes you feel hungry. Why is perceived hunger so important? Because research has highlighted hunger as a compounding factor in the reasons many diets fail.10
Studies have repeatedly shown increases in ghrelin levels following calorie-restricted weight-loss diets. One study out of the New England Journal of Medicine showed a 24 percent increase in ghrelin levels following a six-month weight-loss diet.11 In a more recent study, researchers from the University of Oklahoma investigated a male bodybuilder during a six-month prep phase and witnessed around a 40 percent increase in ghrelin levels after six months of dieting!12
If you continuously diet or have dieted several times in the past, it’s likely that your baseline ghrelin levels are elevated. This could be bad news if you want to stay lean year-round or diet again in the future.