You've successfully lost pounds through dieting, but where does the fat actually go? Dr. Mariëtte Boon, an internist in training at Leiden University Medical Center and co-author of the book Vet Important, shares the science.
There are two main types of body fat: brown and white. White fat—the type most of us want to reduce—consists of fat-filled cells scattered under the skin and around organs. On average, adults carry about 14 kilograms of white fat. Brown fat, by contrast, is far less abundant at around 300 grams, located in the neck and along major blood vessels. These cells act as energy factories, burning fats and sugars to generate heat.
Read also: 'Scientifically proven: nuts help with weight loss'
Brown fat's primary function is thermoregulation. When exposed to cold, it activates within minutes to produce heat, sparing energy from shivering. Standing in 17°C (63°F) temperatures for two hours daily can even boost brown fat levels and enhance overall fat burning.
White fat is equally vital, storing energy from fats and sugars that organs use as fuel.
During metabolism, fat undergoes a chemical reaction in organs, transforming into energy compounds, water, and carbon dioxide—which you exhale. The energy powers muscle contractions and organ functions, while water circulates through the blood, tissues, and is partly excreted in urine.
When you create a calorie deficit through exercise and balanced eating, fat is released from white fat stores and oxidized by organs. Brown fat contributes too, converting white fat into heat. In essence, lost fat becomes usable energy, heat, water, and exhaled CO2.
Text: Maike Abma
