This may seem like a silly question, but it's one we've all pondered at least a few times along our weight-loss journeys [1]. Where does the fat go when we lose weight? Do the fat cells burst and flush out? Do we expel it during bathroom breaks [2]? Do little fairies fly in at night and swipe away all that unwanted jiggle? Let's get into the science, dispel some myths, and answer some (fat-)burning questions.
First of all, there is a difference between weight loss and fat loss. Weight loss is an overall decrease in the number on the scale [3]. This could be from water loss, muscle loss, fat loss, or even getting a drastic haircut (and no, we're not referencing your bangs in high school). Fat loss, however, is the amount of body fat we lose, and this is done when the body burns off more calories than it consumes in a given day.
According to certified personal trainer Heather Neff, "To lose fat, you need to rev up your metabolism with plenty of exercise and good nutrition." But you can't live without fat. It's as indispensable to your body as muscle, blood, and bone!
Sounds crazy, right? The truth is that fat doesn't make you fat [5], as many have been led to believe; "it helps to burn fat and aids in so many body processes," Neff said. Fat is the delivery system for hormones. It is essential for brain function, muscle growth, and so much more. Now before you jump for joy on the way to the nearest Dunkin' Donuts, I have the unenviable task of making it clear that we're talking about healthy fats that can be found in foods such as avocados, eggs, lean meats, organic dairy, nuts, seeds, bananas, and others.
OK, so you can't exactly cut fat out of your system, but where does fat go when you lose it? The answer to that may surprise you. According to a study [6] by Australian physicist Ruben Meerman and University of New South Wales professor Andrew Brown, the majority of the "lost" mass is breathed out as carbon dioxide. The research, published in the British Medical Journal [7], suggests that many doctors and dieticians still harbor the misconception that fat is converted to energy, heat, or muscle. In reality, as Mr. Meerman points out in a news release [8], it simply "goes into thin air."
So the fat doesn't leave your body in the form of urine or feces (well, not completely). If you lose 20 pounds, just over 80 percent of that is going to be exhaled by the lungs, and the remainder will be excreted via urine, feces, sweating, and tears (happy ones, we hope).
All of this might make you rethink your next workout [10] in favor of some breathing exercises to ramp up your fat loss. Unfortunately, you cannot lose weight simply by making yourself breathe faster (hyperventilating). It doesn't work that way. It happens through a metabolic process, so don't go making yourself light-headed. Just keep your metabolism in check by moving during the day and eating whole, healthy foods. Also drink plenty of water [11], because it needs to be replaced as we lose it faster during exercise through sweat and respiration. Eventually, the weight will come off and it'll mostly be expelled through your breath — but you'll only see real results by working out and eating right.