Just before I get back to the prolonged fasting and weight loss post I thought I'd put this picture up.
It's slightly modified for clarity and taken from Fig 1 of this paper.
None of the 10 people in either column are being dieted, the graphs would be different under caloric restriction. I would, all things being equal (ie a linear relationship from thin through obese to a BMI of 50), expect the obese subjects to use/lose more adipose calories per day in proportion to their obesity if you suddenly withdrew all food.
There's more on the study here, which has all of Fig 1 and has not been subjected to my activity with a rubber (OK, an eraser if that's less risque).