Breaking the First Law of Thermodynamics

After hearing that some studies indicate that dieting can sometimes lead to an increase in weight, I wondered how they were violating the First Law. I mean, the body can’t store calories it doesn’t take in, right? I still think that’s the law is true, but things other than calories can apparently generate fat cells. If it turns out to be true that a virus can do that, expect someone to work on a vaccine.