Here is the thing, if you want explanations then you will look up further. Chances are though you just want the guidelines now and you'll ask questions later. So here you go.
1)Eat For Your Goal-
If needing to lose weight eat below your caloric needs. No more than 30% cut.
If needing to gain weight then eat above. Increase by 15% as needed.
Figure that out by going here.
BMI Calculator 2) Eat for Balance-Get at least 30% of every nutrient in a day (protein/carbs/fats). The other 10% is to do whatever you want with it.
3) Eat the right foods-This goes as follows.
Protein-Lean and Complete (chicken, turkey, egg whites, whey)
Carbs-Fruits and veggies should make up the majority of your
diet and be paired with every meal.
Fats-Poly/mono
fat balance high(fish oils, nuts, olive oil);Low Saturated fats
4) Eat Often- Eat 4-6 meals a day.
Each meal should contain 1 complete protein.
Each meal should contain 1 carb source of either fruit/veggies.
5) Eat 1 ingredient items-85% of your meals should be of one ingredient items.
An apples ingredients are an apple. An egg is an egg. You can certainly mix and match on ingredient items, but other than that your items 85% of the time should only be 1 ingredient items.
6) Drink Water-1/2 to 1 gallon a day for women who
exercises, 1 to 1 1/2 gallon for men who exercise.
That's it. If you stick to that you will get results, plain and simple.