Full without food: Can surgery cure obesity? - health - 02 September 2009 - New Scientist

Full without food: Can surgery cure obesity? - health - 02 September 2009 - New Scientist


Over the past decade, genetic and endocrinological research has pointed to a complex set of hormones and neural signals that control food intake (New Scientist, 9 August 2003, p 38). There seem to be two systems at work: one that aims to keep body-fat stores constant over long periods of time, and another that controls food intake over the course of a day.

It is this short-term control mechanism that has been thrust into the limelight thanks to gastric bypass surgery. "Suddenly, the signalling from the gut has turned out to be much more potent than people believed - and possibly a better drug target," says Nick Finer, an endocrinologist at University College London.

Our digestive system produces both hormones that make you hungry and those that make you feel full, or sated. Ghrelin, produced by the lower part of the stomach, is a powerful promoter of hunger, while the small intestine releases a number of hormones when it senses the presence of food. These aid digestion as well as producing feelings of satiety, and include cholecystokinin, glucagon-like peptide-1 (GLP-1), oxyntomodulin and PYY.

Current thinking is that changes to the levels of any or all of these hormones could be responsible for the effects of the bypass. Shrinking the stomach seems to reduce ghrelin production, which would curtail hunger signals. A bypass also delivers nutrients to the more distant parts of the small intestine faster and in greater quantities than normal, which would stimulate the release of more satiety hormones.

The other surprising outcome from bypass surgery is its effects on type 2 diabetes, a condition in which people can no longer regulate their blood sugar. After eating, the pancreas normally releases insulin, a hormone that reduces excess glucose in the blood. In type 2 diabetes, though, the body cannot respond to insulin properly or the pancreas fails to make enough of the hormone, or sometimes both.

Type 2 diabetes is much more common in people who are overweight, and it was expected that the weight loss following a bypass would improve symptoms. But doctors have been amazed by just how quickly this happens - sometimes in a matter of hours and certainly long before any significant weight loss occurs. Many bypass patients have been able to throw away their diabetes drugs. "If you change the anatomy of the bowel, you improve diabetes like nothing else has ever done," says Francesco Rubino at Cornell University-New York Presbyterian Hospital in New York. The upshot is that bypass surgery is now being considered for diabetics of lower and lower weight - perhaps even approaching normal weight if their diabetes is severe enough.

(see "A surgical cure for diabetes?").

new glucagon and GLP-1 co-agonist eliminates obesity