The response to your question is in the post above mine. A basic class teaching the law of conservation of mass and the first law of thermodynamics should be required in every high school and college in this country.
The more muscle mass you have, the more calories you require to maintain that muscle mass. Also, maintaining that muscle mass requires effort (ie, exercise), which also requires calories.
Body composition (ie. The amount of fat and muscle a person has) determines BMR. Fit people who lift heavy and have larger muscles get to eat more calories, as long as they maintain their muscle.
Beyond that, your question doesn't make any sense to me. Even a person who consumes zero calories will not "disappear". They will die from malnutrition before that happens.
For arguments sake, let's think about the extreme example of this. 3500 calories a week is 500 calories a day. My BMR is roughly 1400 calories. If i cut back to 900 cal a day, here is what would happen:
In the short-term, I would lose fat, but over time I would also lose the muscle I've built 1) because I'm not eating enough protein to maintain that muscle, 2) I would not have enough energy to work out and exercise those muscles, and 3) eventually my body would start consuming those muscles for energy.
As I lost muscle my BMR would drop, because the less you weigh, the less calories you need to to maintain that weight.
If I severely restrict my calories over the long term, my body will start shutting down certain non-essential functions to conserve calories - that's why anorexic people start to lose their hair and women stop having a period. They aren't consuming enough calories to maintain those body functions.
There are a lot of other health problems caused by chronic undereating, but ultimately what it does is puts extra stress on the heart which can cause heart failure.
No one will "disappear", but think about severely malnourished people (like those who were found in concentration camps in WWII Germany) - they literally were skin and bones and looked like walking skeletons because they had lost all their fat and muscle.
The more muscle mass you have, the more calories you require to maintain that muscle mass. Also, maintaining that muscle mass requires effort (ie, exercise), which also requires calories.
Body composition (ie. The amount of fat and muscle a person has) determines BMR. Fit people who lift heavy and have larger muscles get to eat more calories, as long as they maintain their muscle.
Beyond that, your question doesn't make any sense to me. Even a person who consumes zero calories will not "disappear". They will die from malnutrition before that happens.
For arguments sake, let's think about the extreme example of this. 3500 calories a week is 500 calories a day. My BMR is roughly 1400 calories. If i cut back to 900 cal a day, here is what would happen:
In the short-term, I would lose fat, but over time I would also lose the muscle I've built 1) because I'm not eating enough protein to maintain that muscle, 2) I would not have enough energy to work out and exercise those muscles, and 3) eventually my body would start consuming those muscles for energy.
As I lost muscle my BMR would drop, because the less you weigh, the less calories you need to to maintain that weight.
If I severely restrict my calories over the long term, my body will start shutting down certain non-essential functions to conserve calories - that's why anorexic people start to lose their hair and women stop having a period. They aren't consuming enough calories to maintain those body functions.
There are a lot of other health problems caused by chronic undereating, but ultimately what it does is puts extra stress on the heart which can cause heart failure.
No one will "disappear", but think about severely malnourished people (like those who were found in concentration camps in WWII Germany) - they literally were skin and bones and looked like walking skeletons because they had lost all their fat and muscle.