A hormone that plays a major role in preventing people getting fat may also help guard against Alzheimer’s disease, new research suggests.

Leptin, which was only discovered back in 1994, helps regulate people’s appetite and gives them signals that tell them they are “full”, stopping them from over-eating.

Studies have shown that obese people tend to have lower levels of leptin or are resistant to it in much the same way diabetics are resistant to insulin.