- Start with 1000 calories from protein (250 grams).
- Protein is converted into glucose (gluconeogenesis) at a 57% efficiency rate.
- So 1000 calories (250 grams) from protein is converted into 570 calories (142.5 grams) worth of glucose.
- 300 calories burnt during digestion due to the thermic effect of food.
- 190 (33% of 570) calories burnt during the conversion process, the cost of gluconeogenesis is 33% of the energy content of the produced glucose.
Digesting and converting 1000 calories from protein into glucose requires 490 calories while only yielding 570 calories. You burn 490 calories to produce 570 calories worth of glucose, an 80 net calorie gain after starting with 1000 calories (8% energy efficiency rating, 0.32 is 8% of 4, this is how we arrive at 0.32 net calories per gram of protein).