Researchers say the new diet pill - fexaramine - tricks the body into thinking it has eaten a meal, which triggers a fat-burning process, causing weight loss.
Ronald Evans, director of the Gene Expression Laboratory at Salk, says the new diet pill - called fexaramine - acts 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. But there are no calories and no change in appetite," he explains.
Evans and colleagues recently published their findings in the journal Nature Medicine.
Fexaramine targets the body's farensoid X receptor (FXR) - a protein that is involved in food digestion, fat and sugar storage and the release of bile acids from the liver.
The researchers explain that when we start eating a meal, FXR is activated in preparation for food intake. Past studies from Evans and team have indicated that as well as triggering the release of bile acids to aid digestion, FXR alters blood sugar levels and switches on a fat-burning process.
Some existing diet pills activate an array of pathways controlled by FXR - including the intestines, liver, kidneys and adrenal glands.
Fexaramine, however, only activates the FXR pathway linked to the intestines. When taken orally, the diet pill is only absorbed in the gut and does not enter the bloodstream, meaning it is unlikely to cause the side effects typically associated with existing diet pills - such as high blood pressure, dizziness, insomnia and even heart disease.
What is more, the fact that fexaramine only acts in the intestines means it is a more effective weight loss aid, according to the researchers, as the drug is not transported throughout the entire body.
The researchers further explain how fexaramine works in the video below:
'Body's response to a meal is like a relay race; we've learned how to trigger the first runner'
To test the effectiveness of fexaramine, Evans and colleagues gave obese mice a daily dose of the drug for 5 weeks and compared the outcomes with mice that remained untreated.
The mice given fexaramine stopped gaining weight and saw a reduction in body fat, blood sugar and cholesterol. What is more, the body temperature of the treated mice increased, indicating a heightened metabolism, and some of the rodent's white fat deposits were converted into healthier, energy-burning fats.
The team says they also saw a change in the assortment of bacteria in the gut, but they note that they are unclear on what this indicates at present.
Evans says fexaramine is more effective than diet pills that trigger numerous FXR pathways because it activates the mechanisms by which the body naturally responds to a meal. He explains:
"When you eat, you have to quickly activate a series of responses all throughout the body. And the reality is that the very first responder for all this is the intestine.
The body's response to a meal is like a relay race, and if you tell all the runners to go at the same time, you'll never pass the baton. We've learned how to trigger the first runner so that the rest of the events happen in a natural order."
Obesity is a major problem in the US, affecting more than a third of adults. Evans and colleagues believe fexaramine is a promising candidate to reduce obesity and the risk of its related diseases - such as type 2 diabetes - in humans.
They hope the drug would be used alongside diet and lifestyle changes under the guidance of health care professionals.
The team is now in the process of setting up clinical trials to assess the effectiveness of fexaramine in humans.
Last month, Medical News Today reported on a study published in the Proceedings of the National Academy of Sciences, which claimed the year in which a person was born may influence their risk of obesity.