It's more along the lines that it's hard to calculate caloric needs -- we see people cycle through phases where their needs are really high and yet they will still have weight loss or body recomp or both.

Our best hypothesis is that this is because they are starting with substantial health problems, and what's needed to deal with that, in terms of energy and substrate, is never factored into calorie calculations

To give one example, GI issues. The surface area of the GI tract, if you include the villi, is about the same as the size of a tennis court. All of that tissue needs to be repaired and restored, that's going to take a lot of protein and fat for the cells and membranes. These people have also been malnourished due to the poor absorption of nutrients from their damaged GI tract, anemia is one of the common problems, and that has to be resolved. They would have been under-muscled (& had the lower bone density that goes along with it) and that gets fixed. And so on. The length of time for this to get better is about 6 months for someone young and older people can take longer, a lot of improvement at the beginning, but really years to reverse damage that was ongoing for decades. It's not a quick fix, it just stops the damage and allows gradual repair of tissue.

Going by the extra appetite without gain that people have, it's about an extra 500-2,000 calories.

After the initial period, everyone tends to settle into a narrower range of the quantity of food that they eat, which roughly fits ideas about being proportional to height and activity level.

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