What you eat or don't eat is one of the most important factors of your overall daily performance. You need not only calories in order to continue expending energy, but you need various nutrients (vitamins and minerals) to keep you functioning properly. The best advice is probably to eat small amounts of a large variety of foods instead of eating primarily the same foods all the time. If you are a picky eater, you need to start learning to like new food. Period! Once you are willing to eat lots of different foods from different food groups, you are on your way to better health. The tricky part, when it comes to your diet, is controlling your weight while maintaining good health and proper levels of energy for long periods of time. The secret to this is knowing about how much of each food groups you need to eat each day. Of course, this varies one source from another.
I enjoy a good conspiracy theory just as much as the next guy, but the truth is I don't think our government intentionally gives us false information concerning our health. I wouldn't doubt that there is some information held back for one reason or another, but I don't think we need to turn the "food pyramid" upside down just because it is endorsed by our government. Over the last several years, the main changes that have been made to what is published by the United States Department of Agriculture has been the art design and adding a few explanations regarding "whole grain," "good fats," the importance of exercise, etc.
It is interesting to point out the differences in "food pyramids" from one country to another. Consider the following diagrams from www.foodpyramid.com (click picture to enlarge):
I personally like the following pyramid the best, apparently based on scientific research from Harvard School of Public Health . This is the one I will be recommending (with the exception of alcohol, which I don't recommend for any Christian to use). Note, however, that staying well hydrated is very important to the way your body functions. I recommend 6-8 glasses of water per day as a minimum.