People who eat whatever they want and stay slim have a slow metabolism, not fast. A skinny person tends to have less muscle mass than others, meaning their basal metabolic rate (BMR) is lower than those of a high muscle mass – this gives them a slow metabolism, not a fast one.
100 Mind-Blowing Metabolic Facts
Your brain burns 400-500 calories a day. That’s about a fifth of your total energy requirements. Most of this is concerned with the largely automatic process of controlling your muscles and processing sensory input, although some studies show solving tricky problems increases your brain’s metabolic requirements too.
Your brain uses 12 watts of energy to think and does not feel pain. The brain uses 20% of our resting metabolic calorie rate to keep functioning. It does not feel any pain because there are no pain receptors in the brain itself.