In 1994, Zhang et al discovered the Ob gene and the hormone leptin1. This brought about the idea that obesity might have genetic-related factors and may not simply involve lack of self-control and overeating in the individual. The Ob gene regulates the amount of body fat storage in the body2. When the Ob gene signals, the hormone leptin is secreted from adipocytes1 and it travels to the hypothalamus in the brain2. This signals the hypothalamus to induce a feeling of satiety2. In other words, leptin secretion causes the stomach to feel full and ceases the necessity for eating. Once this discovery was made, the idea of obesity treatment came into play. If a hormone with satiety-inducing effects can be utilized for treatment then obesity may possibly become a null issue. Unfortunately this is an issue that still stands today – 20 years after the discovery of leptin.
Research into leptin treatment began on rats. A 1996 study by Chen et al showed beneficial results in rats when treated with exogenous leptin3. The rats treated with leptin showed decreased food intake and did not see any weight gain compared to the other groups that were treated with saline. This study basically confirmed the effects of leptin – increased satiety leading to reduced food intake. In this case, there was no weight gain as opposed to the other groups that saw significant weight gain. Leptin, then, can prevent weight gain.
So leptin can prevent weight gain in rats. While that is great and all, the real beneficial impact from leptin will come if it can have the same effect in humans. Research has shown that exogenous leptin treatment can promote weight loss in both lean and obese individuals4. Obese subjects were prescribed a reduced calorie diet to supplement the leptin therapy. This leads to the deduction that due to leptin’s biological function of inducing satiety, the individuals were able to maintain their reduced calorie diet with greater ease because they did not feel hungry as often. However, lean subjects were prescribed a eucaloric diet. This shows that leptin’s role in energy balance may extend further than simply inducing satiety. Because leptin therapy shows the ability to induce weight loss with both a eucaloric diet and reduced calorie diet, it seems reasonable to say that leptin therapy may have a significant impact on weight reduction in the obese population.
Another study showed similar results. Two obese individuals treated with leptin injections demonstrated significant weight loss5. The participants lost weight throughout the duration of the treatment period. The researchers even noted that there were some refractory periods but they were overcome simply with a dosage increase. Here is a table displaying the effect of leptin therapy on body composition5:
Leptin actually excelled beyond just affecting weight loss. The participants in this study also displayed elevated levels of insulin which, as the researchers note, is normal for their age and obesity...