Dr. Jeffrey Friedman Discusses Obesity and His Discovery of Leptin

Dr. Jeffrey Friedman, award-winning scientist who discovered leptin, recently sat down to be interviewed as part of the “Giants in Medicine” series. Friedman, who grew up in New York City, first came to science from a medical background. While he was in medical school, he realized he didn’t want to be a doctor. A series of happenstance events placed him in a laboratory on a “gap year”, studying addiction and how it relates to molecules.

He says, “At the time, I was in a bit of a quandry. All my colleagues were out practicing, starting their lives, and I wasn’t sure what I wanted to do.” However, after some soul searching, he joined the phD program at Rockefeller. The ob/ob mouse fascinated him, and he worked to discover why this particular mutation had occurred. What he found, in the end, was leptin, a hormone that regulates food intake and even plays a role in obesity.

Friedman points out that, while leptin could potentially be used as a treatment for obesity, the answer is more complicated. Leptin simply allows people to maintain a relatively healthy weight. Some people, who are leptin-deficient, lose weight when given leptin treatments. “Normal” people, however, who do not have that mutation, may become leptin-resistant, which is harder to treat. Friedman says, “We have this biological system that maintains body fat within a particular range. In the ob mouse and similarly affected humans, there’s a mutation in the gene so there’s no signal that’s ever generated that there are adequate fat stores and animals and humans who have leptin mutations overeat voraciously. In both cases, if you replace the leptin the body weight normalizes. So, leptin as a treatment for leptin deficiency is very robust.”

Friedman explains that “Most obese humans and most obese animals are obese for other reasons that lead them not to be leptin deficient, but rather, leads them to be leptin resistant.” He says that lower doses of leptin may be more effective than larger ones, and that combining leptin with amylin, another hormone, could be most effective.

When asked about the obesity epidemic, Friedman says, “Whether or not there’s an obesity epidemic depends on how you look at the data.” He points out that, while the increase in obesity rates is a medical condition that needs to be addressed, the data may be sensationalized. He explains that when you assign a fixed point to obesity, that any shift in this data would lead to a seemingly-large shift. He says, “Over the same intervals where obesity rates are said to increase over ⅓, you see maybe a 7 to 10 pound weight change.”

And what advice does Friedman offer to those who may be obese? “Eat a heart healthy diet, exercise, and if you are overweight and have a co-morbidity, do your best to lose a modest amount of weight - say, 7 - 10 pounds, because that’s often enough to improve your health.”