It is well known that in most human subjects ketosis appears -when the material metabolized becomes restricted to protein and fat. This condition is observed after several days of fasting, on diets deficient in carbohydrate, and in diabetes in consequence of the loss of ability to metabolize carbohydrate. These facts have led to the view that a certain minimum combustion of carbohydrate is necessary to avoid ketosis.

The diet of the Eskimo has long been recognized as an apparent exception to this view. Being restricted almost wholly to animal tissues and containing therefore, only a very small proportion of carbohydrate, such a diet might be expected to produce a ketosis. Similar diets fed to human subjects of temperate zones do so. Although the fact appears not to have been investigated, it has been assumed that Eskimos, do not exhibit ketosis on their customary diets. To account for this assumed fact it has been suggested that the Eskimos must possess an adaptation to non- carbohydrate diet.