Who would ever have imagined that two diets with an identical calorie count - high-carb and ultralow carb - would have such vastly difering results in terms of fat loss and muscle gain. After all, energy-in equals energy-out, and it all gets balanced in the end, regardless of when we train and when we eat. At least that’s what we’ve been told for decades.
To the “experts,” this is simply an exercise in the first law of thermodynamics, which states that energy is neither created nor destroyed. In other words, the total energy of the system must be the same, before and after which means that 500 calories of carbs will produce the same result as 500 calories of protein or fat.
The first law of thermodynamics, however, doesn’t mention anything about efficiency in terms of how the body converts this food into energy. It also tells us nothing about what happens if more or less of this energy is wasted depending on what types of macronutrients we’re taking in.