[smashd]

I have experimented with adding other veggies, but it just ends up adding complexity and allows worse choices to sneak in over time. It's easier for me to deal in absolutes in this matter.

Potatoes have a great balance of nutrients and provide satiety in a way that no other food does. I can (and do) eat 2 pounds of potatoes a day, which is about 800 calories. That leaves me with 1,200 calories of "space" (assuming a 2,000-calorie diet) where I can introduce the variety you speak of at dinnertime--2 or more vegetables, a protein (typically legumes or meat) and fruit or another starch. The restriction to potatoes during the day simply blocks out a lot of "bad variety" in the form of convenient junk foods: in my experience, a potato is a better food choice than most of the foods pushed at me while I'm working, running errands, etc.

The 24-hour version of the diet is usually only done for 3 days at a time. It provides sufficient macros during that time period and also provides a better micronutrient balance than most U.S. citizens get from their current diets.