New diet pill could serve up "imaginary meal"

A new diet pill in development that tricks the body into thinking it's eaten a satisfying meal may pave the way for a new generation of weight loss aids.

Researchers at the Salk Institute in La Jolla, Calif. have created a compound called fexaramine that they say works differently than other diet drugs. Unlike supplements that claim to speed up the metabolism or serve as an appetite suppressant, this new pill remains in the intestines and appears to cause fewer side effects.

The researchers say it's like an "imaginary meal."

"It sends out the same signals that normally happen when you eat a lot of food, so the body starts clearing out space to store it," Ronald Evan, director of the Salk's Gene Expression Laboratory and senior author of the new paper, said in a press release. "But there are no calories and no change in appetite."

In a study on mice, their pill effectively stopped weight gain, lowered cholesterol and reduced inflammation. The Salk Institute hopes to push forward and test the pill in human clinical trials. The results of this first animal study were published Monday in the journal Nature Medicine.

Evans and his team spent more than two decades studying the farensoid X receptor (FXR), a protein that is partially responsible for how the body releases bile acids from the liver, digests food and stores fats and sugars. The body turns on FXR at the start of each meal. The receptor triggers the release of bile acids that help aid digestion but also change blood sugar levels and cause the body to burn some fat.

A number of pharmaceutical companies have for some time been working to develop a drug that activates FXR, but such drugs have been shown to have too many side effects. Evans and his team sought to create a drug that turns on FXR only in the intestines, rather than the intestines, liver, kidneys and adrenal glands all at once.

The researchers found when they gave a group of mice a daily fexaramine pill for five weeks, the mice stopped gaining weight, lost fat and had lower blood sugar and cholesterol levels than mice that were not treated. The mice were also found to have higher body temperature than mice that were not given the drug, indicating a higher metabolism. The researchers say some white fat deposits in the mice's bodies converted into healthier, energy-burning fats. The collection of gut bacteria also seemed to change in the mice that were given the drug, though the researchers aren't sure why.

The researchers say that because fexaramine doesn't enter the bloodstream, it is likely to be safer for humans than the drugs that that target all FXR pathways in the body. The researchers say if the drug were to become available, a person could use it under the guidance of a doctor along with a diet and exercise plan to speed up weight loss.