This Is What Actually Happens to Fat When You Lose Weight

Have you ever had an existential moment when you're in the middle of kicking your workout's butt and you stop to wonder... Where does all the fat go when you lose weight?

Do those fat cells just shrink smaller and smaller until they disappear completely? Is the sweat that's currently pouring off your body actually just tiny drops of transformed fat? Is it a mythical process in which the weight loss fairy waves her magic wand over your body while you sleep?

The answer is bizarre and we guarantee it to blow your mind: You breathe it out.

"Most of the mass is breathed out as carbon dioxide," physicist Ruben Meerman, MD, told POPSUGAR. "It goes into thin air."

You read that right. When you lose weight, the fat that you're losing is expelled from your body via your lungs — well, most of it. There's an 80/20 rule that says roughly 80 percent of the fat you lose will be expelled through your lungs, while the rest of it is evacuated through your urine, feces, sweat and tears.

Unfortunately, if you're getting any smart ideas about skipping your next workout for a quick hyperventilating and crying "exercise", your efforts will be in vain. That's because fat has to go through a metabolic process before it can tell your body "adios."

Just make sure to keep your metabolism in check by moving throughout the day, eating healthy and whole foods, and by drinking plenty of water. (All that carbon dioxide and sweat from your workout has to be replaced somehow!)

Oh, and if you're kicking yourself for not knowing about the whole secret CO2/sweat/tears fat loss thing, don't fret — even some doctors are confused on the subject.

"There is surprising ignorance and confusion about the metabolic process of weight loss," professor Andrew Brown, head of the UNSW School of Biotechnology and Biomolecular Sciences, told POPSUGAR.

Plus, in a study Brown conducted, over 50 percent of 150 doctors and dietitians surveyed were led to believe that fat was converted to energy or heat, or even converted into muscle.


So next time your measurements are down a few inches or you notice some muscle definition that wasn't there before, thank your trusty lungs for helping get rid of that pesky extra fat.