Calories and Weight Loss

Everybody throws the word “calories” around, but not many people truly understand what a calorie is, or exactly how the number and different types of calories, and the different ways that they are used in the body, relate to weight loss. Here’s the scoop:

A calorie is a unit of energy. When your body needs energy, your body burns  calories from the food you eat or from the calories stored in your body in fat, glucose (or glycogen) and/or protein.

Calories in food

Foods provide calories. Whenever you eat or drink, the calories you take in are used or stored for later use. Here are some examples of the amount of calories provided by different foods.

    •   A slice of bread has about 65 calories.

    •   An apple has about 50 calories.

    •   A beer has about 200 calories.

    •   A candy bar may contain about 250 calories.

    •   A piece of chocolate cake may have 400 calories.

    •   A super-loaded cheeseburger may have up to 800 calories.

Keep in mind that this number is rarely exact because the portion size and exact ingredients makes a difference. So not every apple will have exactly 50 calories, and not every serving of lasagna will have, say, 300 calories.

Types of Calories

There are different types of calories that provide energy. These are known as the macronutrients: protein, carbohydrates and fat. (Alcohol also provides some energy but is not considered a main fuel source.) At the same given amount, each of these substances provides a slightly different number of calories:

    •   One gram of protein equals four calories

    •   One gram of carbs equals four calories

    •   One gram of fat equals nine calories

So fat has twice the amount of energy as the same portion of protein or carbs. That is why it is easy to take in a large amount of calories if you eat a high fat diet—a small amount packs a big punch.

Which food has what type of calorie?

Most foods contain combinations of protein, fats and carbs, and all forms of calories should be included in your diet. There are very few foods that consist of only one type of calorie.

For example, while people commonly think of bread as a 'carb' food, in fact, bread contains carbs and protein calories, and if it's olive-bread, for example, may contain fat calories, too. The majority of calories may come from carbs, but you get a mix. Nuts and beans contain a mix of carbs, protein and fats.

Meats are not just protein, but contain a mix of protein and fat calories.

Your daily calorie intake

How many calories you eat all day is considered to be your daily caloric intake. If you eat 2,000 calories per day, then a portion of this total amount will consists of fats, protein and carbohydrates. The USDA dietary guidelines recommend that your overall diet consist of 20 percent to 35 percent fat, (saturated fats should be less than 10 percent), 45 percent to 65 percent carbohydrates, and 10 percent to 35 percent protein. So, for example, if you were to eat 25 percent fat, then a 2,000 calorie-per-day meal plan would contain about 500 calories worth of fat overall—or about 56 grams of fat over the day (500 calories divided by nine grams of fat).

Since most foods contain a mix of these macronutrients, it’s not easy to figure out these percentages unless you keep a very detailed log with very comprehensive calculations. For example, if you ate a handful of nuts you would have to break down the amount of protein, fat and carbohydrate calories in that portion and add it to your daily totals.

The most common way to determine your macronutrient breakdown is to enter one or more days of your complete food intake into nutrition analysis software. These programs will analyze the type and amount of each food item and then provide a total of the distribution of nutrients you have consumed. You can assess your food intake on the USDA Web site MyPyramid.com.

You can also use food labels to assess your diet. However, you can’t go by a single label to determine your total day’s intake; you must tally the total calories and nutrient amounts for everything you eat in a day.

It is OK to include some foods that are considered to be high in fat such as avocados, nuts and olives. Not only are these high in fat, they are high in “good” unsaturated fats, and also high in other nutrients. As long as they consist of only a portion of what you eat in a day, they will not cause you to have a high-fat diet. On the other hand, if you eat lots of fast food or junk food that is fried or made with saturated or hydrogenated fats and oils, it is very likely that you would have a diet that is, overall, very high in fat.

You can find out the nutrient breakdown for specific foods from the USDA National Nutrient Database. Simple enter the food type and amount.