UCLA researchers made a startling discovery: genetic alterations enable mice to convert fat into carbon dioxide. Mammals digest fats differently than bacteria — so researchers introduced bacteria genes into mouse livers, and ‘the excess fat was literally released into thin air.  The research potentially could help treat serious medical conditions including diabetes, heart disease — and of course, obesity.

via Technology Review: Making Fat Disappear.: Engineering mice with a fat-burning strategy from bacteria keeps the animals thin. The genetic alterations enabled the animals to convert fat into carbon dioxide and remain lean while eating the equivalent of a fast-food diet.