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Assuming zero carbohydrate intake, during the first 3 weeks of a ketogenic diet a protein
intake of ~150 grams per day should be sufficient to achieve nitrogen balance. Therefore,
regardless of bodyweight, the minimum amount of protein which should be consumed during the
initial three weeks of a ketogenic diet is 150 grams per day.

After 3 weeks of ketosis, as little as 50 grams of protein per day should provide enough
glucose to achieve nitrogen balance. The inclusion of exercise will increase protein requirements
and is discussed in chapter 9.

Carbohydrate intake

The consumption of carbohydrate will decrease dietary protein requirements since less
glucose will need to be made from protein breakdown. For example, if a person was consuming
125 grams of protein per day, this would produce 72 grams of glucose plus 18 more from the
breakdown of glycerol for a total of 90 grams of glucose. To avoid any nitrogen losses, this
individual could either consume 10 grams of carbohydrate per day or simply increase protein
intake to 150 grams per day.

Summary

Looking at the topic of protein sparing from a purely theoretical standpoint, a protein
intake of approximately 150 grams per day should be sufficient to prevent any nitrogen losses
during the first three weeks of a ketogenic diet. After this time period, as little as 50 grams of
protein should be necessary to prevent nitrogen losses. These values are examined by looking at
specific studies in the next section.

Section 3: Nitrogen sparing:

The studies

Having examined protein requirements from a theoretical standpoint, we can now see how
the values determined previously compare to the studies done on ketogenic diets at varying
calorie levels. Before examining some key studies, a discussion of nitrogen balance and how it is
determined is necessary. Additionally, some of the problems with nitrogen balance are discussed.

Protein losses and nitrogen balance

There are many methods of measuring protein losses during dieting and starvation (7).
Without exception all make assumptions and simplifications. From the standpoint of the
ketogenic diet, some methods are better than others, but none are perfect.