While skipping meals to lose weight is not recommended, knowing how many calories you can burn in one day without food is a basis for how many calories you should take in on a daily basis. Your basal metabolic rate, or BMR, tells you the amount of calories your body needs if you were to stay in bed for 24 hours. This formula is based on your age, gender, height and weight.
Your body needs a specific amount of calories to keep your heart beating, lungs breathing, blood circulating and body temperature normal. A regularly functioning body will burn calories when at rest in order to execute these functions. Therefore, even if you were to stay in bed for a full 24 hours, you would still be burning calories. If these calories are not replenished, then you would lose weight.
To determine how many calories your body burns at rest, you need to figure out your personal basal metabolic rate. You will need your age, weight in pounds, and height in inches for the formula. If you are a male, multiply your weight by 6.23 and add that to 66. Multiply your height by 12.7, and add that to the previous number. Now subtract your age multiplied by 6.8. For example, let's take a 200-lb., 6-foot tall man who is 30 years old. Multiply 200 by 6.23 and add that to 66, equaling 1,312. To that, add 72 multiplied by 12.7, equaling 2,226.4. Now from that, subtract 30 multiplied by 6.8. The final BMR would be 2,022.4. If you are a woman, multiply your weight by 4.35, height by 4.7, and age by 4.7. Add your weight number to 655, add that to your height number, and subtract your age number from that.
The BMR formula will estimate the amount of calories you burn solely based on your age, gender, height and weight. Anyone with your same statistics will reap the same number. What this does not take into account is your body composition. A person with little body fat and a lot of muscle mass will burn more calories at rest than someone with a higher body fat percentage. Similarly, if your age increases, weight fluctuates or height changes, your BMR will change as well.
BMR and Weight Loss
One pound is equivalent to 3,500 calories. Considering the example, if the person burned approximately 2,000 calories when at rest, he could potentially lose just over half a pound if he were to do nothing all day and not eat. While this may work for one day, it is not a recommended solution for weight loss. If weight loss is your goal, a regular exercise regimen and healthy caloric intake will be the best way to achieve what you're after. If your body is neglected of nutrients and calories, it will eventually go into starvation mode and hang on to the fat and weight that it does have for fear that it will not be fueled adequately. If you are having trouble losing weight, visit your doctor or a nutritionist for a specialized program tailored to your needs.