First and foremost, grab a pencil, paper, calculator and calculate your Basal Metabolic Rate (BMR) and macro nutrient requirements. BMR Lets say your target is to be a 160 lbs. with 10% body fat (BF). This means you're roughly 10% BF and 90% Lean Body Mass (LBM). So, 90% of 160 is equivalent to 0.90 * 160, which comes out to 144 lbs. LBM. Now convert this to kilograms by dividing 144 by 2.2, which is roughly 65 Kg. Using the Katch-McArdle formula, we get 370 + (21.6 * 65). This comes out to about 1800 kcal. This is your Basal Metabolic Rate, or BMR. It's roughly the amount of calories required to maintain 65 Kg of LBM. BMR does not take into account activity levels, only sitting around on your ass. In order to calculate your total calorie requirement, you have to multiple your BMR by a certain factor based on your activity level: 1.2 = Sedentary (Desk job, and Little Formal Exercise) 1.3-1.4 = Lightly Active (Light daily activity AND light exercise 1-3 days a week) 1.5-1.6 = Moderately Active (Moderately daily Activity & Moderate exercise 3-5 days a week) 1.7-1.8 = Very Active (Physically demanding lifestyle & Hard exercise 6-7 days a week) 1.9-2.2 = Extremely Active (Athlete in ENDURANCE training or VERY HARD physical job) Let's say your moderately active, so you'll want to tack on an extra 50% to your BMR, bringing up your total daily requirement (TDR) to around 2700 kcal. Protein Easily the most debated requirement known to fitness. Bottom line, most research points to 0.6-1.0 grams of protein per pound of LBM, with little, if any, benefit after 1 gram per pound. For 144 pounds of LBM, this would be ~85-150 grams of protein a day. You can eat more protein than this, if you want, just make sure not to exceed your TDR, which is 2700 kcal per day in this example Carbs & Fats 0.4-0.6 grams of fat per pound of LBM is a decent target if you're looking for low body fat. No real guidelines here, just make sure not exceed your TDR, which is 2700 kcal per day in this example. Supplements Creatine Monohydrate, 5g daily. Multivitamins and/or Fish Oil if you don't eat properly. In summation, using this example you would want to eat 55-85g fat, at least 85g of protein, and limit your daily intake to around 2700 kcal per day. Pretty simple stuff, really.