Nova: Is a calorie a calorie?
Is a Calorie a Calorie?
By Malden Nesheim and Marion Nestle
Ever since the 19th century, nutritionists and the general public have accepted the “calorie” as the unit of choice for describing the energy content of food. Yet some scientists still debate whether all food calories are the same.
Do calories from a chocolate bar, for example, have the same effect on your waistline as the same number of calories from an orange? Putting it another way—and getting to a oft-invoked question in the debate—will you be more successful losing weight with calories from a low-fat diet than with the same number of calories from a low-carbohydrate diet? Or might the reverse be true? (As protein typically occurs in low amounts in foods—10 to 15 percent in the average diet—a low-fat diet is necessarily a high-carb diet, and vice versa.)
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