Not all the nutrients and other substances in foods that contribute to good health have been identified, so eating a wide assortment of foods helps ensure that you get all of the disease-fighting potentials that foods offer. In addition, this will limit your exposure to any pesticides or toxic substances that may be present in a particular food. Sure, you can eat all the broccoli and spinach you want, but for higher-calorie foods, portion control is the key. In recent years, serving sizes have ballooned.

Aim for 2½ cups of vegetables and 2 cups of fruit a day, for a 2,000-calorie diet. If you consume more calories, aim for more; if you eat fewer than 2,000 calories, you can eat less. Include green, orange, red, blue/purple and yellow produce.