Ghrelin, famously known as the “hunger hormone” was discovered in relatively recently, in 1999, taking over the stage as a young master player in diverse biological functions, including learning and memory, gut motility and gastric acid secretion, sleep/wake rhythm, reward-seeking behavior, taste sensation, and glucose metabolism.
Have you ever wondered why, even though losing weight can be tough, maintaining your weight after a diet is even harder? Research revealed that a large percentage of dieters regain all the weight they lost within just one year. Ghrelin is one of the factors to blame! As it is an appetite-increasing hormone, its secretion in the stomach tends to rise before meals and the signal of hunger is sent to the brain. Interestingly, studies have shown that after obese people eat a meal, ghrelin only decreases slightly. Because of this, the brain doesn’t receive as strong of a signal to stop eating, which can lead to overeating. But once you start a diet, your ghrelin levels will start to go up even by 40%, suggesting that the longer you diet, the higher your ghrelin levels will rise, making you hungrier and hungrier, so it becomes much harder to maintain your new weight. Talk about a vicious cycle…
Also, did you notice that if you get a full night’s sleep, you probably won’t be feeling that hungry when you wake up? That’s because, during sleep, your body tamps down on ghrelin. It has been reported that only two days of sleep-deprivation caused over 20% elevation in ghrelin levels, and consequently increased hunger and appetite.
Another approach how to keep your ghrelin at check is burst training (e.g. 30-second sprint with breaks in between (goodbye long cardio pieces of training!) as confirmed by a study showing that ghrelin concentrations declined after high-intensity sprinting and stayed lower after 30 minutes of recovery than they were pre-exercise.
Speaking of a vicious cycle, chronic stress also causes ghrelin to rise, leading you to overeat and ultimately gain weight (who hasn’t experienced stress munchies?). So, it turns out that your body’s natural defense against stress is causing you to eat more, causing you to gain more, causing you to stress more.
In summary, ghrelin seems to be one fierce little hormone that can master our hunger on many levels. Until scientists discover a molecule that can help us fight back and block ghrelin’s undesirable effects (good news: there’s a candidate called LEAP2 recently discovered), we should get to know to our body’s coexistence with ghrelin more closely in order to tame it…