Infants (the demographic with the lowest incidence of chronic disease and most positive central nervous system regulation) do best when they drink breast milk. There are some rare abnormalities, like chylothorax, wherein this isn't the case; but generally it's true. Breast milk content varies, but on average the macronutrient content in energy (as opposed to volume) is about 50% fat, 10% protein and 40% carbohydrates. Babies are growing rapidly, thus their carbohydrate needs are relatively high.
How does this instruct us as adults? Well, if you're in a rapid growth cycle like babies, which really only pertains to bodybuilders or people trying to accelerate their cancer cell production, then you want to move your carbohydrate intake up to 40% or more. It will raise blood sugar, stimulating the pancreas to produce insulin which grows ALL TISSUE especially those cells which are upregulated for growth. Upregulated cells would include muscle cells after a workout, or cancer cells if you have cancer, or fat cells if you are sedentary. Also, insulin creates insulin resistance, leading to degeneration and aging.
What does all that mean? If you are trying to maintain or have moderate increases in strength or muscle, carbohydrate intake other than fiber should be severely limited, except immediately following some workouts and/or in the evening when fat cells are most difficult to grow. If you are really active, like a 90 year old Okinawan karate teacher on his feet all day, then you might benefit from a little more white rice in the diet.
By virtue of decreasing carbohydrate percentage, this means that your fat and/or protein intake will go up. If you want to grow fat at half the rate of a baby, there is a strong argument that a good balanced diet should look like 60% fat, 20% protein, 20% carbohydrates (again, not including fiber).
If you don't want to grow fat at all, especially if your activity level isn't very high (keep in mind, kids move a lot more than you, and nature doesn't peg their carb needs higher than 50% of total calories), then dietary fat most likely should be higher. If you haven't done any heavy lifting, 15% or fewer calories coming from protein is probably fine, meaning fat percentage could go as high as 80+%.
If you still think that dietary fat intake increases your risk of heart disease or some other ideas pulled from 1950s American nutrition science, please please please watch Gary Taubes' Googletech talk for free online and read my earlier blog posts.