Nutrition and Metabolism
Core concepts
Understand macronutrients and micronutrients, energy balance, basal metabolic rate, and the thermic effect of food. Know the caloric content of macronutrients, the roles of vitamins and minerals, and the distinction between water-soluble and fat-soluble vitamins. Familiarity with digestion and absorption, glycemic response, protein quality, and dietary reference intakes is expected. Understand metabolic pathways at a conceptual level, including glycolysis, fatty acid oxidation, and ketogenesis.
Traps
Questions often confuse fat-soluble and water-soluble vitamins: fat-soluble vitamins (A, D, E, K) are stored in the body and can accumulate to toxic levels, while water-soluble vitamins are excreted more readily. Another trap is assuming that all calories are metabolized identically; macronutrient composition affects satiety and thermogenesis. Watch for questions that confuse dietary reference intake categories, such as recommended dietary allowance versus adequate intake.
Worked example
A food label lists 20 g carbohydrate, 10 g protein, and 5 g fat. Using 4, 4, and 9 kcal per gram, energy = (20 × 4) + (10 × 4) + (5 × 9) = 80 + 40 + 45 = 165 kcal.
Study tip
Memorize the 4-4-9 rule and the fat-soluble vitamin list; many nutrition items are simple recall or arithmetic built on these two facts.