Fat burning
Fat burning goes on around the clock – what matters isn't the fat-burning zone during exercise but your energy balance over the whole day.
Ausführlich erklärt
Your body burns fat all the time – while you sleep, sit, walk and train. Whether you end up losing fat isn't decided by a single workout, but by whether you use more energy over the course of the day than you take in. Burning fat and losing fat are two different things: fat is always being burned, but you only lose it when your energy balance is negative.
The myth of the “fat-burning zone” is stubborn. What's true is this: at an easy pace, the body draws a larger share of its energy from fat; at high intensity, more comes from carbohydrates. But a share isn't the same as an amount. If you run briskly for 30 minutes, you burn more calories overall – and usually more grams of fat, too – than on a 30-minute walk. And the carbohydrates used up during training are then replenished from what you eat instead of being turned into fat. In the end, total energy expenditure is what counts. So the best workout is the one you can keep up regularly.
Where does the fat go? Into the air. Fat consists of carbon, hydrogen and oxygen; when it's broken down, carbon dioxide and water are produced. In 2014, an Australian research team did the maths: of ten kilos of fat, 8.4 kilos leave the body through the lungs as CO₂, while 1.6 kilos become water and are lost through urine, sweat and breath. You literally breathe out your fat – but only if a deficit triggers the breakdown; breathing faster on its own does nothing.
What really influences fat burning: muscle mass and movement increase energy expenditure; protein is filling and costs energy to digest; sleep and low stress keep cortisol and hunger in check. Caffeine and green tea measurably increase energy expenditure, but only by a few dozen calories a day – “fat burner” capsules don't deliver on their promises, and some are a health risk. Nor can you lose fat from one specific part of your body: where it disappears first is down to your genes.
With children, it's better not to talk about “burning fat” – for them, movement is play, strength and fun, and that's exactly how it should feel.