Issue 119 Item 4 New Hormone Injection Cuts Calories Consumed by One-Third

The most effective obesity agent ever discovered. An injection of a gut hormone cuts by a third the calories consumed by people offered a free lunch, researchers have discovered. It could be an effective new treatment for the large and growing problem of obesity.

"The discovery that the hormone suppresses appetite could be of huge benefit to those struggling with weight problems," says Stephen Bloom at Imperial College, London, who led the research. "With over a billion people across the world now extremely overweight, it is vital this problem is tackled."

The hormone, called PYY3-36, is normally released from the gastro-intestinal tract after eating. The higher the calorific content of the meal eaten, the more hormone is released. The team also conducted research on rats, which suggests PYY3-36 travels to the hypothalamus in the brain and blocks the activity of neurons involved in triggering eating.

Bloom and his colleagues injected 12 healthy people with enough of the hormone to replicate the levels expected after eating a meal. Two hours later, these people and volunteers injected with an inactive liquid were given access to a free buffet. The treated 12 consumed one third fewer calories than the controls – and the reduction in appetite continued for about 12 hours.

This is the most effective appetite-reducing agent yet discovered "by quite a margin," Bloom says.

Bloom thinks the hormone could be on sale as an anti-obesity drug in four years, if clinical trials go well. "It would cost the same as insulin, and be injected in the same way," says Bloom.

The proportion of obese people in the UK has tripled since 1982, to about 20 per cent of the adult population. In the US, the figure is 26 per cent. Obesity is linked to a variety of serious health problems, including heart disease, diabetes and some cancers.

The rapid increase in the numbers of obese people worldwide is fuelling research into the factors that regulate appetite. Late in 2001, a team that included Bloom reported that injections of a hormone called ghrelin boost calorie intake in people by almost 30 per cent. Nature (vol 418, p 650)