The only thing that matters is metabolism. I approach everything from this front now. Calories should be intaken with metabolism in mind, not weight loss, satiety, or any of that silliness. Weight loss will follow metabolism anyway. I came up with a way to describe metabolism with a single number, based upon waking body temp && pulses, since I found it difficult to mentally combine them without a mathematical descriptor. I'm now using this # in my database to optimize my diet.
Essentially:
% Optimal Body temp = Measured waking body temp divided by 98.6 (truncate to 100% if over 98.6)
% Optimal Waking pulse rate = Measured waking pulse rate divided by 85 (truncate to 100% if over 85)
I agree metabolism is the most important factor, although even Broda Barnes wouldn't have found anything wrong with a waking temp around 98.0 +/- 2 (97.8-98.2). It's perfectly normal to not be at 98.6 upon waking up. 98.6 is the typical midday temp of a healthy human. 98 is a good number to shoot for as a basal (morning) temperature.