There is some truth to the old adage that you are what you eat. Consume plenty of nutrient-rich fruits, vegetables, whole grains, low-fat dairy products, and lean protein, and you’ll be giving your body the right fuel to stay healthy and full of energy for your daily activities. If you fill up on fatty, sugary, or salty processed foods, on the other hand, you could end up missing out on key nutrients and setting yourself up to gain weight and experience lagging energy.

As far as good nutrition goes, certain guidelines are universal, whether you’re a man or a woman, younger or older. The current nutritional recommendations suggest that you get 45 to 60 percent of your daily calories from complex carbohydrates, 20 to 30 percent from lean protein, and 20 to 35 percent from fats (less than 10 percent of calories from saturated fats, and as little as possible from trans fats). It’s also best to limit your intake to a maximum of 300 milligrams of cholesterol and 2,300 milligrams of sodium per day as well as to try to consume 25 to 35 milligrams of fiber per day.

Essentially, these guidelines translate into a diet that is rich in fruits, vegetables, and whole grains. Since no single food contains all the nutrients your body needs, be sure to choose a variety of foods from within each food group: Different colored fruits and vegetables, a host of whole grains, and various sources of protein (from eggs and beans to fish, poultry or meat). Men require slightly greater amounts of the vitamins A, C, K, B-6, thiamin, riboflavin, and niacin, as well as the minerals chromium, magnesium, and zinc, mostly because they tend to be larger than women; menstruating women, on the other hand, need to get more iron in their diets than do men or older women. As a result, your food choices may be affected. 

You can combine foods from each major food group in any way you like, but do keep a close eye on your portion sizes. As portion sizes increase in the U.S., obesity rates are on the rise. Indeed, research has found that the more you’re served, the more you’re likely to eat in one sitting. That’s why it’s smart to learn what a proper serving should look like. Some handy rules of thumb to keep in mind:

Proper Portion Size Equivalents

1 cup of cereal or 1 baked potato = the size of a clenched fist

1 cup of cooked rice or pasta = the size of a baseball

1 medium fruit or 1 cup of fruit or salad greens = the size of a tennis ball

1 1/2-ounce serving of cheese = the size of four stacked dice

3 ounces of meat or poultry = the size of a deck of cards

3 ounces of grilled or baked fish = the size of a checkbook

2 tablespoons of salad dressing or peanut butter = the size of a ping pong ball

1 teaspoon of butter or margarine = the size of one dice

1/2 cup ice cream = the size of 1/2 baseball