Good nutrition is essential for not just fitness but also general overall health. Our bodies need Nutrients: carbohydrates, proteins, fats and additional macro-nutrients: water, vitamins, minerals, to process those nutrients. Without them we would cease to exist.
A foundation for nutrition is very simple. Most people know the foundation but rarely practice it. An ideal nutritional plan consists of 5-6 small meals eaten throughout the day consisting of carbohydrates, proteins, and fats. The phrase "In the morning eat like a king, at lunch eat like a prince and at dinner eat like a pauper" holds the basic concept, although it does need to be "Tweaked" a bit.
Your morning meal is the most important meal of the day, yet many people do not eat breakfast. They hurry off to work or school with a cup of caffeine and no food. They make statements that they don't have time or if they eat they are hungry all day. Time is what you make of it; leftover meals (like cold pizza) make a great breakfast if you don't have time to make one. If you are hungry all day you may need to change what you have for breakfast, doughnuts taste good, but good breakfast consists of carbohydrates (preferably low glycemic), protein, fat.
Your next meals should also contain a portion of carbohydrates, protein and fat and be spaced 2-4 hours apart. As the day progresses you should watch your carbohydrate intake, with your last meal have little to no carbohydrates. If you know that you are going out for an evening meal, plan you carbohydrates to be lighter during the day which will give you balance for the evening. One meal in the evening is not going to be an issue unless you make it one.
Many people tell me that they don't eat after 6:00 at night. My question to them is why. If you finish your meal at 6:00, got to bed at 10:00 and sleep for 8 hours and then don't eat until noon, you are running on 18 hours with no food (or fuel). This is not good. There is a pretty good chance that your body will go into starvation mode. Your last meal before bedtime should be mostly protein with little to no carbohydrates (no ice-cream). This depends upon the daily meal intake and the dinner meal and of course what time the meal is eaten and your fitness level.
When creating a nutritional program, you do not need to add extra fat. You can get your 30% by eating properly and food preparation.