How many calories are provided by food that contains 20 grams of carbohydrates, 8 grams protein, and 5 grams of fat?

A. 157

B. 232

C. 258

D. 378

It would be A. 157

Step-by-step explanation:

This is actually really simple when you study Keto diet, where being ketogenic is the easiness on how a specific Macronutrient (Carbohydrates, protein and fat), transform into glucose, a standard rule of 4-4-9 (Carbs-Protein-Fat) is usually applied.

So fat is 90% ketogenic, thus having a caloric proportion of 9 calories per gram of fat.

Carbohydrates are 100% antiketogenic, so it turns mostly into glucose, this would mean that a ratio of 1-10 on grams to calories would be acceptable when talking about carbs intake (1 gram would be 10 calories), yet it is not. There is a myriad of choices of carbs, for example, fiber is technically categorized as a carbohydrate, yet it is not processed easily on our organism, in fact fiber provides about 2 calories per gram. To simplify calculations, an average of 4 calories per gram is used when calculating calories (yet keep in mind this is only an approximation).

Meanwhile, protein is 46% ketogenic, meaning 4.6 calories per gram of protein, it is simplified to 4 for easiness of calculations.

Then the formula is simple:

Calories = (grams of Protein + grams of Carbs) * 4 + (grams of Fat) * 9

Calories = (20+8) * 4 + (5) * 9 = 112+45 = 157