But as CBS News Correspondent Elizabeth Kaledin reports, researchers at Boston's Joslin Diabetes Center may have the answer. They've figured out a way to let mice eat all they want while staying slim, avoiding diabetes and living longer at the same time.
Dr. Ronald Kahn led the research and discovered that by knocking out a gene in the mice that controls fat storage, the mice can eat all day long without gaining an ounce.
The difference is striking between the mice and their siblings, one which has been genetically altered and one not.
Of course, like a calorie-free dessert, it sounds too good to be true. The research is, after all, only in mice. But even obesity experts like Dr. Louis Aronne say the finding could change the way we think about the causes of weight gain.
"What the study tells us is that the key factor is how much fat you store ... not how much you eat," said Aronne.
Dr. Kahn believes there's no reason we can't alter the same genes in people, offering new treatments for the obese.
"We have a chance, we do have a chance, to find ways to alter the metabolism of fat such that you could eat and not get fat," said Kahn.
The question is: If such technology is available to people some day, won't it give us license to eat everything in sight? Won't a healthy diet and exercise become casualties of a magic pill? Dr. Kahn hopes not.
"The goal here is not to create a way to stay thin and eat everything you want," he said.
The goal instead, he says, is to help those who cannot help themselves.