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takyon writes:

A study has found that mice with an impaired sense of smell gain less weight than other mice, even when calorie consumption and exercise levels are the same:

To conduct the study, molecular biologist Andrew Dillin of the University of California, Berkeley, and colleagues turned to a variety of genetically altered mice. The scientists gave them regular doses of the diphtheria toxin—which causes a temporary loss of odor-sensing neurons—to suppress their sense of smell. They then fed the rodents either a normal diet or fatty foods—the mouse equivalent of cheesecake and pizza—that usually induce obesity.

After more than 3 months of noshing on regular chow, the odor-deprived rodents weighed slightly less than mice whose sense of smell was intact. In the group on the high-fat diet, however, the mice that couldn't smell weighed 16% less than animals that could [open, DOI: 10.1016/j.cmet.2017.06.015] [DX], which became obese. Losing the ability to smell also caused a different group of already-obese mice to lose weight, the researchers reveal today in Cell Metabolism. The obvious explanation for this effect—that mice with impaired olfaction were eating less—turned out to be wrong. There was no difference in the animals' food consumption. Nor were the slim rodents getting more exercise. They weren't moving around their cages more than their porky counterparts.

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