A calorie, by definition, is the amount of heat energy it takes to raise the temperature of a gram of water by one degree Celsius. Food chemists analyze the energy stored in our foods using instruments like the bomb calorimeter. Experimenters literally burn foods and measure how much heat gets released. Scientists have figured out the following:

• One gram of fat has nine calories.
• One gram of protein has four calories.
• One gram of carbohydrate has four calories.

More Calories in Fat Than in Other Macronutrients

So fat is more “energy dense” than protein or carbohydrate. What might that tell scientists about obesity and weight loss? The conventional wisdom suggests that all calories are “equal” to the body. When the amount of energy that goes into the body exceeds the amount of energy that leaves the body, weight gain will occur, according to this theory. To get rid of fat, the caloric balance must be shifted to the negative. Thus, high calorie foodstuffs, such as high fat foods like bacon and fatty hamburgers, should be more obesogenic than low energy density foods, like rice and wheat. After all, gram for gram, fat contains more energy.

Why Counting Calories Makes No Sense

While it is inevitably true that the calories entering the body must equal the calories that leave it (otherwise the first law of thermodynamics will be violated), most obesity researchers and dietitians make a fundamental mistake when it comes to this discussion about calories. They assume that the excess energy that people eat will be immediately deposited in the fat tissue. But fat tissue metabolism is extremely complex.

There are massive books written about the many different enzymes and hormones and genetic factors and other factors that regulate fat tissue metabolism. Why is this important? It is crucial because different kinds of calories impact fat metabolism differently. A calorie of carbohydrate, for instance, may drive the pancreas to secrete the hormone insulin, which can play a key role in triglyceride storage in the fat tissue. A calorie of fat, however, tends not to elevate insulin levels and thus tends not to favor the storage of triglycerides in the fat tissue. Most obesity researchers overlook how important fat tissue metabolism is to the entire question of caloric balance.

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