Q&A: Is a Calorie Just a Calorie and Are You Eating The Kool-Aid?
Today, Cindy explains once and for all why all calories are not created equal.
A. Five hundred calories of broccoli simply do not equate to 500 calories worth of, say…fried Kool-Aid.
Calories are complicated. A calorie is the unit of measurement we use to signify the amount of heat a food can produce. In the early 19th century, the calorie was used to explain the theory of heat conservation behind the steam engine.
The term entered the food world around 1890 when the USDA appropriated it for a report on nutrition.
To apply this concept to foods like sandwiches, scientists used to set food on fire (really!) and then gauge how well the flaming sample warmed a water bath. The warmer the water, the more calories the food contained. (Today, a food’s calorie count is estimated from its carbohydrate, protein and fat content.) In the calorie’s leap to nutrition, its definition evolved. The calorie we now see cited on nutrition labels signifies the amount of heat required to raise one kilogram of water one degree Celsius.
Here’s the problem: Our bodies aren’t steam engines. Instead of heat, they run on chemical energy; we’re fueled by the oxidation of carbohydrates, fats and protein that occurs within our cells. Calories alone do not fuel our bodies; the equation is much more complex. The carbohydrate, protein and fat composition of a food – as well as the calories of each respective nutrient – are all factors in how the body is fueled.
Protein, carbs and fat are all metabolized differently, so the ”calories in equals calories out” theory is not entirely accurate. For every 100 carbohydrate calories you consume, your body expends 5-10 calories in digestion. With fats, you expend slightly less (although thinner people seem to break down more fat than heavier people). The calorie-burn champion is protein: For every 100 protein calories you consume, your body needs 20-30 calories for digestion. This is one of the reasons why it’s important to eat protein at each meal if you’re looking to lose weight.
To break things down further, animal sources of protein are more digestible than plant sources, so a lean cut of beef will be better absorbed than tofu. And as we know, carbs are also processed at different rates: Glucose and starch are quickly absorbed while fiber digests much more slowly. In fact, the insoluble fiber in complex carbs like vegetables and whole grains can even block the absorption of other calories! It’s important to keep all of these factors in mind when you’re trying to change your body weight.
Cindy makes some great points. There’s a lot more to energy balance than just calories; the types of food you eat do matter.
So chew on that, and NOT THIS!
And quit drinking the Kool-Aid, too.
Filed under: exercise Q&A, nutrition
