Understanding Calories

Calories are the way we measure the amount of energy in foods and the amount of energy that the body uses. The nutrients in food that provides the calories come in the form of fats, proteins, and carbohydrates. These 3 nutrients are found in all of the major food groups and foods may have one or more of each kind of nutrient. There is a fourth source calories but it is not a nutrient, alcohol also has calories in it.

Each source of calories provides the body with different amounts of calories per gram.

1 gram of carbohydrate contains 4 calories
1 gram of protein contains 4 calories
1 gram of fat contains 9 calories
1 gram of alcohol contains 7 calories

You can use these figures to calculate the number of calories per serving. If a food is made up of only fat and there are 8 grams of it, here is how you figure out the calories in that food:

8 grams of the food times 9 calories (for each gram of fat) equals a total of 72 calories.

Another example: if the food has 3 grams of fat and 4 grams of protein, you calculate each nutrient separately and then add the two together for the total number of calories.

3 grams fat x 9 calories (for each gram) = 27 calories
5 grams protein x 4 calories (for each gram) = 20 calories
Adding 27 fat calories to 20 protein calories equals 47 total calories.

Of course food contains more nutrients than just calories. Food also has vitamins, minerals, and water, which are also necessary to maintain health. When a food has mostly calories and just a few nutrients, they are known as "calorie-dense." When the food has calories along with vitamins and minerals, they are known as "nutrient-dense." For a healthy diet, you need all 3 nutrients in your daily diet.

When you understand calories you can make better choices about the food you eat by choosing foods that provide a good balance of carbohydrates, fat, and protein. But what is a good balance you ask? The US Department of Agriculture and the Department of Health and Human Services publishes dietary guidelines. These guidelines recommend a diet that gets most of its calories from fresh vegetables and fruits, whole grain products, lowfat milk products, lean meats, fish, poultry, and dried beans.

The American Heart Association recommends that:

carbohydrates supply 55% to 60% of the calories
fat calories make up less than 30% of the total (with less than 10% from saturated fat)

Your body's needs calories for energy every day. The specific amount of calories you need depends on several factors. These include:

your weight
your height
your age
body composition (how fat and muscle are distributed in your body)
your physical condition
your activity level
your basal metabolic rate or BMR, which is how many calories the body burns at rest in 24 hours

The exact caloriea each person needs varies over time with changes in stress and activities. See the Calorie Calculator below for estimates.

Once you become an adult, your need for calories drops 2% for each decade. Eating more calories than your body needs results in weight gain. Your body converts the extra calories into fat for future use. Eating less calories than your body needs results in weight loss as your body converts the fat back into energy for your muscles.

Active men and teenaged boys need about 2,800 calories a day to fuel their daily activities. According to the Food Guide Pyramid for this group 2,800 calories would equal about:

11 servings from the bread group
5 servings of vegetables
4 servings of fruit
2 or 3 servings from the milk group (3 servings for teens)
3 servings or a total of 7 ounces of meat

Active women and teenaged girls, and less active men need about 2,200 calories to fuel their daily activities. According to the Food Guide Pyramid for this group 2,200 calories equal about:

9 servings from the bread group
4 servings of vegetables
3 servings of fruit
2 or 3 servings from the milk group (pregnant and breastfeeding women should get 3 servings, teenaged girls and young adults up to age 24 should get 4 servings)
2 servings (for a total of 6 ounces) from the meat group.

Women who are less active, children and some older adults need about 1,600 calories to fuel their bodies. According to the Food Guide Pyramid for this group 1,600 calories would equal about:

6 servings from the bread group
3 servings of vegetables
2 servings of fruit
2 to 3 servings from the milk group
2 servings (for a total of 5 ounces) from the meat group

In order to lose weight your body has to burn more calories than you take in by eating and drinking. Remember that alcohol adds calories with no nutrition. If you are on a weight loss program, drinking alcohol is counterproductive.

How many calories a day do you normally burn? Use this Calorie Calculator to find out.