Congratulations, you got it! Now could you explain that simple principle to the thousands of people who spend $35 billion a year (2006 data) on weight loss diets and foods?
Regarding eating a high protein diet, it will be deficient in nutrients found in whole grains, fruits, dairy and starchy vegetables all of which contain carbohydrates. Fiber will also be low increasing your risk of colon related diseases like diverticulitis or colon cancer.
A variety of foods from all food groups (meat, dairy, starch, fruit, vegetables and healthy oils) is a better long-term solution to weight maintenance as long as portion sizes are moderate. My Plate provides a good template from which to plan your menu. If you would like to try my HELP Healthy Eating For Life Plan® which would create a personalized healthy eating plan incorporating your preferences for the type of milk, meat, beans, and snacks.