[mlurp]

I might have misunderstood what you meant, but it seems like you're saying his problem is that the required deficit to lose that amount of weight in that time is more than a typical daily intake?

If that's the case, it could just mean that his starting intake level was 2*(that deficit), for example. Lots of people just overeat. Apologies if that's not what you meant though.

[mlurp]

Ah sorry, I think I see now. Do you mean that his baseline amount he uses every day is less than the deficit, so even if he consumed nothing, it still wouldn't be enough?

[wizzard]

If they were eating 5,000 calories a day every day before starting the diet (without being a serious athlete), their starting BMI/weight would have been much higher.