[daviddavis]

Nutritional studies are notoriously difficult to conduct. You either have to isolate subjects and monitor everything they eat and when. Or you have to rely on self reported data and people do an atrocious job of tracking food, estimating portion size, etc.

This study did the former:

> The duration of the study is 7 days including 3 days with controlled diet and 4 days (including 5 nights) in a metabolic chamber at the Institute of Nutritional Medicine at the University of Hohenheim.

I imagine it was prohibitively expensive to have more participants.