Review Question - QID 217177

This patient who is hospitalized for anorexia nervosa requires a dietary plan, for which it is essential to understand that macronutrients provide varying numbers of kilocalories per gram (kcal/g): 7 kcal/g for alcohol, 9 kcal/g for fat, and 4 kcal/g each for carbohydrates and protein.

Macronutrients refer to chemical substances (namely, carbohydrates, proteins, and fats) that are required in large quantities for human growth and metabolism. Essentially all macronutrients are obtained through diet; throughout the gastrointestinal tract, each macronutrient undergoes various forms of breakdown and absorption into the bloodstream for subsequent metabolism. Macronutrients are useful for metabolism due to their inherent chemical energy. Importantly, each macronutrient provides a varying amount of caloric energy based on its chemical structure; fats provide 9 kcal/g, while carbohydrates and proteins provide 4 kcal/g. Of note, though not an essential macronutrient, alcohol provides 7 kcal/g, making it relatively calorie dense. Many patients with nutritional deficiencies, obesity, gastrointestinal disorders, and other disorders often require dietary counseling, which often includes a detailed regimen with specific macronutrient goals.

Riera-Crichton et al. revisit the "calories in, calories out" paradigm of weight and weight loss by time-series analysis of the United States between 1974 and 2006, in order to estimate the relative contributions of various macronutrients and physical activity to population-level changes in weight. They find that increased refined carbohydrates significantly contribute to weight gain relative to other macronutrients.

Figure A presents the possible answer choices for this question. Within the answer choices A-E, values are shown for the numbers of kcal/g for each macronutrient (alcohol, carbohydrates, fat, and protein).

Incorrect Answers:
Answer 1: Choice A states that alcohol contains 4 kcal/g, carbohydrates 4 kcal/g, fats 9 kcal/g, and protein 4 kcal/g. However, alcohol contains 7 kcal/g; as such, alcohol is a relatively dense calorie source.

Answer 2: Choice B states that alcohol contains 4 kcal/g, carbohydrates 7 kcal/g, fats 9 kcal/g, and protein 4 kcal/g. However, for alcohol and carbohydrates, the opposite is in fact true, as alcohol contains 7 kcal/g while carbohydrates contain 4 kcal/g.

Answer 4: Choice D states that alcohol contains 7 kcal/g, carbohydrates 7 kcal/g, fats 9 kcal/g, and protein 4 kcal/g. While alcohol contains 7 kcal/g, carbohydrates (along with protein) only contain 4 kcal/g, making them a relatively less dense source of kilocalories compared to alcohol.

Answer 5: Choice E states that all macronutrients (alcohol, carbohydrates, fats, and protein) contain 4 kcal/g. However, macronutrients vary in terms of caloric content; while it is true that proteins and carbohydrates contain 4 kcal/g, alcohol contains 7 kcal/g and fats contain 9 kcal/g.

Bullet Summary:
Dietary intake sources provide varying amounts of kilocalories according to their constituent macronutrients, as alcohol provides 7 kcal/g, fat provides 9 kcal/g, carbohydrates provide 4 kcal/g, and protein provides 4 kcal/g.