In a new book, Robert Lustig, a professor of clinical paediatrics at the University of California, said the hormone leptin - which acts like an appetite thermostat - and sugar may be fuelling the global obesity epidemic.
As one of two 'hunger hormones' in the body, leptin works to decrease the appetite (its partner, ghrelin, increases appetite), the 'Daily Mail' reported.
When you have had enough to eat, your fat cells release leptin, which effectively dulls the appetite by instructing the brain that it's time to stop eating.
More recent studies have shown that obese people have plenty of leptin (in fact, the fatter you are, the more of it you appear to have), but are more likely to be 'leptin-resistant'.
This means the cells in the brain that should register leptin no longer 'read' the signals saying the body is full, but instead assume it is starving.
Lustig and his team in repeated studies on humans found that too much sugar in the diet is behind leptin resistance.
High sugar diets lead to spikes in the hormone. This is needed to clear sugar out of the blood and into storage as fat. But repeated insulin spikes, due to a high sugar diet, can lead to a condition called 'insulin resistance' (when the cells have been so bombarded by insulin they no longer respond to it).
Lustig believes insulin resistance triggers leptin resistance, and, crucially, he has discovered that by reducing insulin levels it is possible to improve 'leptin signalling' (the brain's ability to read leptin), stop cravings, put the brakes on food consumption - and trigger weight loss.
In his new book 'Fat Chance', Lustig explained that leptin resistance
