Someone else may be able to supplement this, but basically phase 2 (and 3) is designed to:
1. Help us eat a low-glycemic diet (i.e., foods that don't cause blood sugar to rise quickly),
2. Keep calories under control.
3. Eat foods with known nutritional or health benefits (including moderate amounts of foods that wouldn't otherwise be included on phase 2),
4. Eat a healthy diet overall.
Eating a healthy diet means we should be eating plenty of vegetables, along with some fruit, whole grains, adequate amounts of protein, and good fats. It also means minimizing saturated fats and foods known to be unhealthy. Calories are kept under control by controlling the type and amount of foods we eat. For example, calorie-dense foods like meats, dairy, nuts, seeds, good fats, and beans are included but the quantity is limited. There's no particular limit for meats, eggs, or protein foods, except that you should eat only an adequate amount, until you're satisfied. Eggs do have fat and cholesterol, but you don't have to eat eggs (people who need to limit dietary cholesterol can skip them), and they are still rather low in fat and calories compared with the fatty meats or poultry we don't eat. Naturally lower-calorie foods like vegetables are emphasized, so we fill up on them instead of the calorie-dense foods.