Your body strives to keep you in a state of energy balance. It wants you to put in and burn off the right amount of calories. Ghrelin and leptin are two hormones that facilitate this process by sending signals to your brain. Ghrelin says, "I'm hungry," and leptin says, "I've had enough." Both are relatively new discoveries to the scientific community, but researchers think controlling ghrelin and leptin will one day be the key to reducing obesity.
Leptin is a hormone secreted by fat cells. When working properly, your body responds to leptin by decreasing your appetite after you've eaten. Leptin also promotes calorie burning. It was discovered by accident in the mid-1990s when researchers found that mice treated with leptin ate considerably less, and mice with less leptin overate. It works the same way in people, with a twist: Obese people have high levels of leptin, but researchers at Harvard and elsewhere think their bodies are less sensitive to its effects. Leptin resistance, as it's known, results in "unnecessarily high food intake," and low leptin levels are a precursor to obesity.
Ghrelin is the hunger hormone. Produced by the stomach, its job is to send a message that you need to eat. Like leptin, it works in the region of the brain in charge of pleasure-seeking, and researchers believe ghrelin also controls "stress eating," makes you crave high-calorie foods and promotes abdominal fat. When you go on an extreme diet, even more ghrelin gets secreted, and your ability to burn calories starts to diminish. The stomach shoots a dose of ghrelin every 30 minutes, but it can speed up to about every 20 minutes if your tummy's empty and you're really hungry. Ghrelin levels fall when food you eat hits your intestines, according to Dr. Michael Roizen, of the Cleveland Clinic.
Hormones and Obesity
Therapies that mimic leptin and control ghrelin are being investigated to treat obesity. More than one-third of the U.S. population is obese, and another third is overweight. Ghrelin-blocking drugs have shown promise as weight-loss agents, according to "Diabetes Forecast," and new drugs that copy the action of leptin are in the works as appetite-suppression agents.
Controlling Leptin and Ghrelin
According to Roizen, your choice of foods and your activity level are like remote programmers of ghrelin and leptin. By eating solid proteins, such as lean meats and nuts in your meals, you stay satisfied longer. Eat simple sugars, and you'll be spiking ghrelin. He recommends you keep an emergency stash of safe foods--such as vegetable juice, a handful of nuts, cut-up fruit and vegetables--to keep hunger at bay. In addition, research from the University of Chicago says sleep deprivation increases ghrelin, decreases leptin and increases the incidence of obesity.
Obesity results when you consistently consume more calories than you burn. Although the causes can be socioeconomic and medical, including hormonal, there's no established medical treatment for obesity. The best way is to eat less and move more. For some, bariatric surgery, which involves modification of the digestive tract, is an effective treatment. According to Weight Watchers, research has shown that people who lose weight may make more ghrelin than before, but people who undergo bariatric surgery produce less ghrelin, which reduces their appetite and helps with their weight loss.
- ShareCare.com: What are Ghrelin and Leptin?
- American Diabetes Association: Hungry? This is Your Brain on Food
- "You on a Diet: The Owner's Manual for Waist Management"; Michael Roizen and Mehmet Oz; 2006
- Harvard Focus: Energy Equation Proposes Patterns of Weight Gain and Loss
- Science Daily: Stomach Hormone Ghrelin Increases Desire for High-Calorie Foods, Study Finds
- American Journal of Physiology: Leptin Resistance--A Predisposing Factor for Diet-Induced Obesity