That may be the case for these new special mice. They can eat as much as they want and not worry about body fat.
In a study posted by the Journal of Biological Chemistry, genetically engineered mice were able to eat unlimited amounts of high-fat mouse chow, but no matter how much they eat they only have about half the body fat of normal mice. Plus, they show no signs of diabetes or other complications with metabolism. How is this possible? Scientists say it's due to a special protein called "Wnt10b." High amounts of this protein stop fat cells from developing and can prevent obesity.
If it sounds too good to be true, you're right. Researchers still have to iron out a couple of less-than-lovely side effects before a fat-busting diet pill hits the market. These leaner mice couldn't generate body heat, leaving them very vulnerable to cold. Other unexplained side effects included underdeveloped mammary glands, decreased oxygen consumption and skin that was twice as thick as normal. Because of this, human tests are a ways away   even if some of us wouldn't mind being thicker-skinned to be thinner-thighed!
Further research will attempt to solve the unanswered side effects, but the low-fat mice are on their way to being patented.