If you don't eat enough, you won't grow as much as you could. What you eat doesn't matter quite as much as making sure you are eating enough - enough calories and enough protein.
No additional comments are needed. I just want to emphasize what Tot said. As much as people will try to analyze their diet to the T - fat ratios, glycemic index levels for carbs, EFA's, macronutrient %'s... it's the amount of calories and protein that makes the difference.
Makes the MOST difference. The body is a complicated mechanism that requires nutrition beyond simple carbs and narrow range proteins for health. At least take a daily vitamin/mineral supp for insurance, if your diet is either very simple or crappy.
IMHO, and a thousand unbiased websites.