In the past, leptin was the buzzword hormone that came up in conversations of hormone-related weight loss and gain. Until now, it was thought that leptin-a hormone that tells your brain to burn fat for energy and tells your body when it is full-was the only hormone involved in weight loss.
"For decades, scientists have been trying to understand why it's so difficult to maintain the weight achieved after the sacrifices of a successful diet and why it's so easy to regain the lost weight, "Donato said. "Leptin has hitherto been considered the main hormone that acts to conserve energy when we're hungry."
During the study scientists saw that weight loss triggered an increase in growth hormone in the hypothalamus, which makes weight loss harder and increases the intensity of hunger. Why do our bodies respond this way? Energy conservation is so important for the organism that evolution has endowed humans with two energy-conservation mechanisms, one activated by leptin and the other by growth hormone. "