Where does fat go when you lose weight?

The internet is filled with explanations of what happens to fat when you lose weight — it’s reborn as energy, converted into heat, made into muscle, exits as No. 1 or No. 2. The truth? Most of that blubber shed turns into hot air.

Surprised? Join the club, says Ruben Meerman, Ph.D., the Australian scientist — who literally wrote the book on misunderstanding flab — “Big Fat Myths,” 

explains that fat is breathed out as carbon dioxide. With Andrew Brown, head of biomolecular sciences at University of New South Wales, he showed the fate of fat from a molecular level.

Fat from food is stored in the body as a compound called triglyceride. Triglyceride consists of three kinds of atoms; carbon, hydrogen and oxygen. When it’s broken down, according to Meerman, 84% of fat becomes carbon dioxide (CO2) and leaves the body through the lungs. The other 16% forms water (H2O) and is drained out as water — urine, feces, sweat, tears and other bodily fluids. This usually surprises people, Meerman says, because “carbon dioxide gas we exhale is invisible.” Unlike your flab.

More than half of docs, dieticians and trainers researchers surveyed thought fat transformed into energy or heat, as in got burned. Nope. And no, you can’t skip the exercise and just breathe heavily to lose weight. You'll just end up hyperventilating.

“My ongoing research,” Meerman told the Daily News, “is about how we can teach this subject better.”