Telling participants in the Diet Fit study to avoid added sugar and refined grains in both low-carb and low-fat groups may have diminished the chance of seeing a significant difference between the diets.

“Well, yeah, actually, we told both groups to have a really healthy diet, and added sugar and refined grains aren't healthy. And he said, 'Well, that's it's going to diminish the chance to see a difference because most people who are eating low carb versus the traditional lowfat do better because the lowfatters eating high carb are eating added sugar and refined grain.”