Mice eating same calories lose weight when sense of smell is impaired. The reason? Increased brown fat activity.

FTA:

Dillin and colleagues found that not only did the brown fat ramp up its activity in the smell-deficient animals, but some of their white fat also became more like brown fat. “They rewire their metabolic programming to burn more calories,” he says. When a mouse can’t smell its food, he speculates, it may “think” that it has eaten more than it really has, prompting it to use more energy.