There is a bit of confusion about the difference between losing one pound of body weight and losing one pound of fat. Let’s look at the math.
How Weight Is Maintained
First we have to look at how losing, gaining and maintaining body weight work.
If you followed my videos about weight loss, then you know that there are two numbers that govern your body weight, the BMR and the TDEE:
- The BMR (“Basal Metabolic Rate”) is the number of calories you burn when you do nothing, simply being alive. Some people believe that lying in bed all day doesn’t burn any energy, but even if you consciously don’t do anything, your heart still has to beat, your cells are being renewed and your hair is growing etc.
- On top of this comes the TDEE (“Total Daily Energy Expenditure”), which is the BMR plus the calories burned for things you actually do. For example, washing the car, going shopping, working out etc.
If your daily energy intake stays below your TDEE, you will lose weight, if you eat around your TDEE, your weight will remain constant, and if you eat above your TDEE, your weight will increase.
If your TDEE is 2,500 kcal and you manage to eat only 2,000 per day, then over the course of seven days you lose one pound of weight. Because it takes a deficit of about 3,500 kcal to lose a pound.
Let’s now look at where the calories come from.
- 1 gram of fat contains 9 kcal
- 1 gram of carbohydrates contains 4 kcal
- 1 g of protein comes with 4 kcal as well
And that’s where people say, wait a minute! One pound is 454 g and if 1 g of fat contains 9 kcal, that would be 4086 kcal – where do those extra 586 calories come from?
Not All Is Fat
The solution is simple: when you lose one pound of body weight it isn’t pure fat, but also the body structure that supported it, which consists of water, connective tissue and protein. As water doesn’t contain any calories, it is easy to see where the difference comes from.
Picture courtesy of Steve Snodgrass.