Below is a table that maps out the average calorie requirement per gender and age. For someone who eats 2000 calories a day, the following portions apply: Grain: 6-8 servings of grain, one serving is a sandwich or half a cup of rice. Vegetables: 4-5 servings of vegetables, one serving is half a cup. Fruit 5-6 servings, one serving is the size of a tennis ball, Lean meat, chicken, fish: 6 portions, 3 portions are the size of a set of playing cards.