Is Ghrelin an Obesity Villain?

Fat Pigs

Ghrelin, the “hunger hormone,” reminds us to eat, in case we forget. It’s like the warning light on a car’s dashboard that tells you to add oil before the engine seizes up. Face-to-face with an opossum, “yum yum” would not be a person’s first thought. It took the survival-stimulating chemical ghrelin to make the connection between obtaining nourishment and continuing to exist.

In the old days, getting food was a lot of work. You had to locate an animal, outsmart or outrun it, kill it, build a fire to cook it with, pull the charred skin off, and so on. Frankly, it would be easier to just lie down and die. Without the nagging discomfort and then actual pain of hunger, early hominids might have decided to do just that, and we wouldn’t be here talking about it.

Ghrelin must have inspired innovation, the desire to try unknown plants to see if they could be eaten, and experimentation with ways of preparing various plants and animals to render them edible. Without ghrelin, many individuals would not have survived, and maybe our whole species would have gone belly-up. How could anyone be so rude as to call it a villain?

What Does Ghrelin Do?

If you want to make a lab mouse fat on purpose, its ghrelin signals and receptors had better be in good working order. When a lab mouse has too much ghrelin, its food preference changes. It doesn’t just want a supersize helping of everyday rat chow, it wants fatty foods with more taste value. Too much ghrelin flips the switch from “eating to live” to “living to eat.”

In humans, chronic psychosocial stress is associated with higher ghrelin production. Prof. Lisa Jaremka and colleagues gathered 42 married couples for a study of the relation between family arguments and overeating. The report says:

Hostile couples had significantly higher amounts of the appetite-triggering hormone after arguments if they were at a healthy weight or in the overweight category, while those who were obese—with BMI 30 or higher—showed no significant difference.

Despite ghrelin’s occasional tendency to make us overeat, nobody would suggest trying to eliminate it from our internal chemical factories. But it would be very useful to know how to keep it within bounds and under control. A Childhood Obesity News post characterized ghrelin as weird because it seems to operate in the realm of psychosomatic overlap, where the placebo effect takes place. A Yale study fed participants 380-calorie milkshakes, but told some of them they had taken in only 140 calories, and told others they had consumed 620 calories, and guess what? The subjects who believed they got more calories actually had lower levels of ghrelin, as would happen if they had truly consumed more calories.

Prader-Willi syndrome is a rare genetically caused disorder in which a chronic overproduction of ghrelin makes the person feel hungry all the time. Because of the condition’s other effects, a newborn will probably have difficulty in feeding. But as childhood progresses, the constant hunger usually leads straight to obesity and a high risk of diabetes.

Recently, a team at the Children’s Hospital of Los Angeles hypothesized that some adults who don’t have Prader-Willi syndrome act like they do have it, because their ghrelin-producing mechanism was somehow damaged in infancy. Experiments with baby lab animals revealed that metabolic dysfunctions can be caused by having either too little or too much ghrelin, so balance is the key. How can balance be achieved? Chris Weller writes:

There are several ways parents can help give their kids a head start in maintaining healthy ghrelin levels, and much of the advice applies not just to developing infants, but to the general public. They can start by putting their infants to bed as often as necessary and not skimping on naptime. One 2008 study showed one night of sleep deprivation raised people’s ghrelin levels. Another way is to keep a healthier diet. High-fat foods have been shown to keep ghrelin levels low for a far shorter time than carbohydrate- or protein-based meals.

Your responses and feedback are welcome!

Source: “Discomfort Food,”, 08/14/1
Source: “Ghrelin Hunger Hormone Poses Obesity Risk For Life When Imbalanced In Infants,” MedicalDaily,com, 01/20/15
Image by Stinging Eyes


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