Q. Can leptin work as an obesity treatment? continued...
According to Atkinson, mouse experiments that began in the early 1970s pointed to "some sort of a hormone that affected food intake and body fat, but [scientists] didn't know what it was."
When researchers finally discovered leptin in 1994, it helped "put obesity on the map because it suggested…obesity may have some physiological basis, instead of just being, "fat people can't keep their mouth shut,'" Atkinson says. "For those of us in the field of obesity, it was a watershed moment. Suddenly, everybody jumped on the bandwagon. This became a frantic obsession with the obesity community, at least."
Many scientists explored leptin as a possible treatment for obesity; they believed that if people were leptin-deficient, giving them leptin would raise levels, which would signal them to stop overeating. "But when you started giving it to people, it didn't work so well," Atkinson says.
"This stuff is made by fat tissue, and as you get fatter, you make more of it. That was quite a shock because everybody thought that obese people were going to be deficient in leptin," he says.
With the more recent understanding of leptin resistance, it makes no sense to give people leptin if they have an impaired response, Lustig says. "The resistance is still there. No amount of leptin is going to overcome that resistance."
Giving leptin only helps in a few extremely rare cases in the world in which people make no leptin at all, which causes them to overeat and become obese. When those people received leptin by injection, they stopped overeating and lost weight. But for the vast majority of people, the treatment won't work, nor is leptin approved as a medical treatment for weight loss.
"Leptin is still sort of experimental. There's no real need to take leptin now, unless you're one of those very small -- probably 100 people in the world -- who doesn't make leptin," Atkinson says.
Q. What about leptin supplements, such as those sold on the Internet?
Because leptin is a digestible protein that doesn’t enter the bloodstream, it can’t be taken in supplement form, Atkinson says. “If you were to take it as a pill, it’s just like eating chicken or beef. It’s a protein and your body would just break it up, so you wouldn’t absorb it from a pill.”