Antonis Damianou: Look at Figure 3A in the study you cite from 1976. You’ll see that ketones (the hallmark of a ketogenic diet) are continuing to rise on day 10 — and at that time had reached less than half the levels of fasting. This figure alone undermines Hall’s argument, that short studies (including his 6-day study) have relevance to understanding the long-term impact of macronutrients on body fatness. It takes a while for someone habituated to a high-carbohydrate diet to adapt to a high-fat diet. There’s simply no value in trials of < 2 to 3 weeks, unless one is specifically interested in studying the process of fat adaptation.