Most people find it difficult to maintain a healthy weight after substantial weight loss? Hunger hormone ghrelin which tricks the bodies into thinking that it needs to eat more, may be the culprit, researchers have shown.

According to Catia Martins, Associate Professor at the Norwegian University of Science and Technology (NTNU), most people with obesity are able to lose weight, even on their own, but only 20 per cent manage to maintain the new lower weight. The study showed that when we lose weight, the stomach releases greater amounts of the ghrelin hormone, which makes us feel hungry. "Everyone has this hormone, but if you've been overweight and then lose weight, the hormone level increases," Martins said.

However, the level of ghrelin does not adjust over time, but remains high. This means it's likely that people who have been overweight will have to deal with increased hunger pangs for the rest of their lives, Martins said. On the other hand, people who have lost weight need less energy to maintain their new and lighter bodies. Yet they feel hungrier, because the body is trying to get that weight back.

The study, published in the American Journal of Physiology, Endocrinology and Metabolism, examined appetite in patients who participated in a comprehensive 2-year weight loss programme. Patients started out weighing 125 kg on average, but lost an average of 11 kg after two years. Two out of ten manage to keep weight down after programme. The research suggested that it's important to know which physiological mechanisms resist weight loss. "People can lose motivation and have trouble following the diet and exercise advice. All of this makes it difficult to maintain the new lower weight," Martins noted. "Obesity is a daily struggle for the rest of one's life. We have to stop treating it as a short-term illness by giving patients some support and help, and then just letting them fend for themselves."