The mirror suggests it; the scales confirm it: You have, through hardcore dedication and/or a terrible stomach virus, managed to lose some weight. But… lose it where? Where does the fat actually go? Do we digest it? Poop it out? Is it sacrificed to appease the appetites of the ancient Sumerian god of fitness, Sixx-Pak?
“Very simply speaking, our bodies are a lot like a car,” explains nutritionist and personal trainer Sean Salazar. Just like putting gas in your car, he explains, that food you’re putting into your body is used as fuel. Unlike your car, though, when you consume way more food than you need, you store it in your body as fat — i.e., excess fuel. In other words, picture a slightly clunky old sedan (or gleaming sports car, depending upon your level of self-esteem) with a bunch of bulging gas cans uselessly tied to the roof.
That’s your belly when you consistently overeat.
To get rid of that fat, says Salazar, we have to be in a “deficit,” where we consume less calories than we’re burning off. A lot less, actually: “To lose a single pound requires consuming 3,500 calories less than usual,” he explains. This means that if you reduce your caloric intake by 500 calories (that’s one bagel with cream cheese, or a Belgian waffle with syrup — or if you’re a healthier eater, five apples) per day, it’ll still take you a week to lose just one pound.
Adding exercise on top of the calorie reduction helps to burn off more calories, meaning you’ll lose more weight. Just like that car engine burns off fuel, your body heats up and burns off the stored fat as energy in a process known as ketosis. “Nothing is wasted in the body,” explains Carolyn Dean, a Medical Advisory Board Member at the Nutritional Magnesium Association. “Fat is metabolized to make glucose [a simple form of sugar], which will produce more energy.”
Once the fat has been burned up by this metabolic process, there are a handful of waste products left over. One of these is carbon dioxide, which “will exit the body through the lungs so that the body doesn’t become too acidic,” according to Salazar. Ketosis also creates heat and water as waste, which are easily dispatched: The heat is dissipated through your skin (either through the evaporation of sweat or the usual radiation of heat outwards from the body), and the water is expelled through sweat and urine.
And where does all that stuff go? The CO2 goes into the air to be breathed in by trees, and the urine, after processing, eventually makes its way back into the rivers and streams.
It’s the circle of—well, fat.