The two primary hormones that control appetite are ghrelin and leptin. They serve as biological on/off switches. Ghrelin is mainly produced in the lining of the stomach and switches on appetite. Leptin is secreted by fat cells and turns off appetite by signaling when you’re full.

Produced by fat cells, leptin signals to the brain how much fat is in the body, explains Dr. Scott Isaacs, medical director of Atlanta Endocrine Associates. When leptin levels are low, you tend to feel hungry, and when leptin levels are high, you tend to feel full.

However, some studies have found that only 5 percent of people have a TSH above 2.5 (though others say it's more like 15 percent). That is to say, being above 2.5 is statistically abnormal. And abnormalities are, by and large, how medicine decides what a disease is.

Diabetes information is everywhere—blogs, online forums, small talk with friends and family, terrifying lawyer ads on TV. Keep in mind that everyone’s situation is different and some sources are more reliable than others, Dr. Isaacs says. Your diabetes care team can guide you toward the truth and help you make the best choices for your health.

If you store your leftovers in plastic, keep old receipts lying around or think nothing of eating an unwashed grape or two, you could be exposing yourself to chemicals that impede weight loss. "These substances slow your metabolism and increase appetite or alter hormones such as estrogen in the body to cause weight gain," says Scott Isaacs, M.D., an endocrinologist and author of Beat Overeating Now!

"In the past 20 years, we've learned a lot about hunger and satiety hormones," says Scott Isaacs, MD, a board-certified endocrinologist in Atlanta and author of Beat Overeating Now! "The first one was leptin, which was discovered in 1994." Since then, many other hormones that impact hunger, appetite, cravings, and weight have been discovered. "Leptin is a hormone that's produced by fat cells, and it works to suppress appetite in the brain," Isaacs explains. "We used to think a fat cell was an inert storage depot for excess fat, insulating the body. But now we know that fat is an endocrine organ, that is, a gland that produces hormones. Leptin is just one of the hormones produced by fat cells." The amount of leptin circulating in a person is proportional to the amount of body fat and indicates how much energy stores a person has.

A healthy diet is well-balanced and includes lean proteins from both animal and vegetarian sources, fruits, vegetables, and nuts,” he says. “Carbohydrates are the component of the diet which have the most significant effect on your blood sugars. Limiting or avoiding added sugars and refined flours can help to keep blood sugars controlled without cutting out healthier carbohydrates such as legumes [beans] and whole grains.

A common misconception is that losing weight quickly is not healthy, not sustainable, and will just lead to future weight re-gain. To the contrary, numerous clinical studies demonstrate that following a lifestyle change program which promotes fast initial weight loss can result in better long-term success.

Having low testosterone levels doesn't necessarily make you gain weight, said Scott Isaacs, MD, an endocrinologist, faculty member of Emory University School of Medicine, medical director for Atlanta Endocrine Associates, and author of Hormonal Balance: How to Lose Weight by Understanding Your Hormones and Metabolism. However, when you gain weight, your testosterone levels will decrease. “Obesity is the number one cause of low testosterone,” Dr. Isaacs said. "Taking testosterone alone rarely results in weight loss. Most patients need to change their eating habits.”

I refuse to use them," says endocrinologist Scott Isaacs, an obesity specialist at Emory University in Atlanta. "In my opinion, there's no good clinical data that they actually work, and I have found that patients seem to regain weight as soon as they stop taking them."