The goal of Zone dieting is to eat the correct balance of carbohydrates and protein so that glucagon is produced instead of insulin, because glucagon promotes the formation of "good" eicosanoids while insulin promotes the formation of "bad" eicosanoids that cause all sorts of diseases.

To reach the Zone, one must consume foods in a protein-to-carbohydrate ratio of 0.75, which is 3 grams of protein for every 4 grams of carbohydrate, at every meal and snack, and without allowing more than 5 hours between meals or snacks. The author converts grams into blocks of protein and carbohydrate and provides food lists and meal plans for these. 

Protein requirements in the Zone are based on lean body mass and level of physical activity (the same method that is used in Protein Power). The lean body mass is calculated using standardized charts that use height, hip and abdomen measurements in women and weight, wrist and waist measurements in men.

The calculated protein requirement is not to be exceeded, and is to be spread throughout the day, to avoid increased insulin levels caused by protein digestion. Therefore, a person would end up with a calorie limit on their total daily intake, since protein has a maximum value, and carbohydrate and fat intake are measured by protein intake. Zone dieting claims to improve numerous health conditions, primarily based on the eicosanoid activities.