I'm sure you've heard the expression, "A calorie is
a calorie." It means that carbohydrate, fat and protein
calories are equal in terms of their effect on body weight.
This point is most often made in the context of debates
between low-carb and low-fat diet advocates.
Those who say "A calorie is a calorie" in this
context mean to suggest that macronutrient proportions are
irrelevant to weight management (as long as one is getting
enough of each to meet one's basic health needs). All that
matters is the total number of calories consumed, regardless
of whether the plurality comes from fat or carbohydrate.
Weight management is a simple game of math, these folks
argue. To maintain your current weight, you need to consume
the same number of calories your body burns each day. To
lose a pound, you need to create a caloric deficit of approximately
3,500 calories. Whether you create that deficit by eating
less fat, less carbohydrate, less protein or a little less
of everything is immaterial.
It sounds sensible, but it's actually not true. A calorie
is not a calorie, in more than one sense. Carbohydrate,
fat and protein calories are indeed equal by definition
in terms of their energy content, but the body processes
each in a distinct way, and these differences have real
implications for weight management. In addition, food calories
of all types may have very different effects on the body
depending on when they are eaten and what they are eaten
with. Following are five specific reasons why all calories
are not equal.
1. The energy cost to metabolize fat, carbs and protein
is different.
2. Calorie restriction slows metabolism.
3. Protein reduces appetite.
4. Fiber reduces calorie absorption.
5. Timing of eating affects calorie processing.
