If the body digested everything with 100% efficiency and didn't produce waste, and also treated all 'calories' equally, then I'd agree that thermodynamics tells

If the body digested everything with 100% efficiency and didn't produce waste, and also treated all 'calories' equally, then I'd agree that thermodynamics tells us everything we need to know. But even people coming from the complete opposite end of the argument to the paleo crowd ("Eat more whole grains!") agree that the amount of heat produced by a substance when it's burnt in a calorimeter doesn't tell the full story about its potential for causing obesity.