When somebody loses weight, Where Does it Go
When fat is broken down in the presence of oxygen (which is necessary), the end products are energy, carbon dioxide (excreted through lungs), and water (excreted through bodily fluids like urine).
Considering the soaring overweight and obesity rates and strong interest in this topic, there is surprising ignorance and confusion about the metabolic process of weight loss among the general public and health professionals alike. We encountered widespread misconceptions about how humans lose weight among general practitioners, dietitians, and personal trainers (fig 1). Most people believed that fat is converted to energy or heat, which violates the law of conservation of mass. We suspect this misconception is caused by the “energy in/energy out” mantra and the focus on energy production in university biochemistry courses. Other misconceptions were that the metabolites of fat are excreted in the faeces or converted to muscle. We present a novel calculation to show how we “lose weight.”