Conditions such as heart disease, obesity and diabetes could be prevented by a "fat controller" in the gut.
The MGAT2 enzyme decides if dietary fat is kept in the adipose tissue resulting in the swelling of the stomach or used to make energy.
Experts researching the gene for MGAT2 discovered that mice missing it were able to have a high fat diet and still stay healthy and slim.
Despite consuming a normal amount of calories, instead of being stored, the fat was burned up.
Scientists also found the mice without MGAT2 did not develop a glucose intolerance, as well as a "fatty liver" and high cholesterol.
Humans and mice have three MGAT enzymes in their intestines including MGAT2. Reducing the activity of MGAT with drugs could help tackle obesity, according to scientists.
Dr Robert Farese, from the University of California at San Francisco, and colleagues, carried out the tests and published the results in the journal Nature Medicine.
Dr Farese said: "Our studies identify MGAT2 as a key determinant of energy metabolism in response to dietary fat and suggest that the inhibition of this enzyme may prove to be a useful strategy for treating obesity and other metabolic diseases associated with excessive fat intake."