10 reasons why your weight fluctuates so much

If you’ve ever wondered why you weigh less when you’re sick or right after recovering from a short cold or flu, there’s a pretty simple explanation. “Even mild illnesses can cause a slight dehydration and quick drop in weight,” says Lisa Hugh, RD. “After the illness, people often complain that they have gained weight. But almost always, it’s really just a dehydration followed by rehydration.”