Calories Expended Vs. Calories Consumed

Calories aren't just a measure of how diet-friendly your meal is; they're a unit of energy measurement. When you expend energy to jog, ride a bike or climb a mountain, you're expending calories. When you eat a 100-calorie serving of yogurt or a 500-calorie slice of cake, you're eating energy. Successful weight loss involves keeping an imbalance between the energy you consume and the energy you expend.

Calorie Balance

When the calories you eat precisely balance the calories you burn, your weight stabilizes. This balance is delicate and ever-shifting, however. Your body converts every additional 3,500 calories it consumes into a pound of stored fat. That amount seems large -- the equivalent of a few days' meals -- but it's easy to reach it through gradual dietary additions. If you were to consume just an extra 100 calories a day -- about the amount you'd get from an extra ounce of chips with your lunch or whipped cream with your coffee -- you would put on more than 10 pounds in a year. An extra can of soda a day translates into about 26 pounds by the end of the year. Conversely, making small calorie subtractions tilts the balance in the other direction and lets you lose weight.

Resting Metabolic Rate

Your body expends energy even when you appear to be doing nothing. Your respiration, digestion, heartbeat, brain activity and other vital processes require energy to carry out. You'll burn a certain number of calories just to continue these metabolic processes. The calories you burn without doing anything define your resting metabolic rate. If you're muscular or overweight, you have a higher resting metabolic rate than someone who is slim. Count this essential energy expenditure when you calculate how many calories you should consume or burn during a day.

Energy Expenditure

In addition to the energy your body uses to keep functioning, the energy you expend voluntarily to work out or go for a walk counts toward your overall calorie deficit. Intentional exercise has clear benefits for weight loss, but unintentional exercise -- the incidental movement called non-exercise activity thermogenesis, or NEAT -- also contributes to weight loss. When you take the stairs instead of the escalator or walk to the store instead of driving there, you're getting additional NEAT and burning more calories.

Calorie Consumption

Every food you eat has calories, but some foods are more calorie dense than others. Fats contain 9 calories per gram, whereas proteins and carbohydrates provide 4 calories per gram. Therefore, foods with a high fat content typically have calorie counts higher than those of lower-fat foods. This difference in calories per gram doesn't mean you should eliminate fats altogether; your body needs fats to process certain nutrients and for healthy connective tissues, among other things. Balance calorie-dense foods high in healthy fats such as avocados and olives with low-fat, low-calorie foods like whole grains and lean proteins for optimal health. Develop the habit of seeing calorie counts as measures of energy; a high-calorie food is not necessarily a bad food, but it contains so much energy that you should eat only a small amount of it to prevent that excess energy from converting to fat.

Calorie Balance in Action

Whether you want to lose weight or gain it, understanding how energy consumption and expenditure work will help you reach your weight goal. Research from the Harvard School of Public Health found no appreciable differences in the speed or magnitude of weight loss across a number of diet types. The study suggests that you should therefore choose the diet that pleases your palate and satisfies your stomach while paying attention to proper overall nutrition rather than eliminating macronutrients from your menu. Just as a pound of feathers and a pound of bricks weigh the same, the units of measurement called calories are the same whether you eat a 100-calorie morsel of candy or a 100-calorie platter of raw broccoli.