It is really quite simple. The problem is that you cannot look at this from a calories point of view. Here is why:
The body does not convert calories, which are units of heat used to model the energy output of food, into body fat. The body stores fat and amino acids/protein only. The amino acid contribution to the energy equation is negligible compared to fat, and usually desirable, so we can ignore that. So, the amount of fat you would store on your body during any given period would have an upper limit of the amount of fat you ate during the same period, irrespective of calories. In other words, if you ate eleventy million calories in only sugar, you, amazingly, would not get fatter.
The actual amount of fat stored would then be the difference between how much fat you burned during the day and the amount of fat you ate. The amount of fat one burns depends on a number of factors, but the deciding factors are:
- Degree of ketoadaption: This refers the fat burning pathways which are usually stunted in those on higher carb diets.
- Activity level, especially time not spent anaerobically.