1 kilogram is equal to 7716.17917647 calories, or 2.20462262185 pounds.

That's the most percise number I have found, however slit seems that they just converted the 3500:1 calorie:pound ratio to a calorie:kilo ratio. That and directly below this article was one about the truth of 6-pack abs so it's credability is in question.

All I'm saying is a mass to energy conversion is not a easy one, especially when the variables of the human body are introduced. You have so many different substances with such varying densities and masses that it's virtually impossible to set a accurate baseline. You can work out every day if you are fairly fit and you will gain weight in muscle mass. I put on 10 pounds last year in muscle.

This isn't pounds of coal into BTUs, it's a little more complex, and all these diet websites probably arnt the most reliable.