Nutrition, Physical Activity, and Body Systems
This domain tests nutrient functions, dietary guidance, energy balance, physical activity recommendations, and physiological responses. Questions often require interpreting a food label or calculating nutrient percentages.
Core rules and concepts
- Energy values: carbohydrate 4 kcal/g, protein 4 kcal/g, fat 9 kcal/g, alcohol 7 kcal/g.
- Dietary Guidelines for Americans: limit added sugars to less than 10% of calories, saturated fat to less than 10%, and sodium to less than 2,300 mg/day; emphasize fruits, vegetables, whole grains, lean proteins, and low-fat dairy.
- MyPlate: half the plate fruits and vegetables, one quarter grains, one quarter protein, with dairy on the side.
- Physical activity: adults need 150 minutes of moderate or 75 minutes of vigorous aerobic activity weekly plus 2 days of muscle strengthening; youth need 60 minutes daily.
- Energy balance: weight change reflects calories consumed versus expended. BMI is a screening tool, not a diagnosis.
- Digestion and absorption: most absorption occurs in the small intestine. Fat-soluble vitamins are A, D, E, and K; water-soluble vitamins are absorbed with water.
- Food safety: danger zone is 40–140°F; discard perishables after 2 hours.
Worked example: A snack has 8 g fat, 20 g carbohydrate, and 5 g protein. Fat calories = 8 × 9 = 72; carbohydrate = 20 × 4 = 80; protein = 5 × 4 = 20; total = 172. Percent fat = 72 ÷ 172 ≈ 42%. Reasoning: use Atwater factors. A food high in total fat is not automatically high in saturated fat; check the label for saturated fat before applying the 10% guideline.
Traps that cost marks: confusing serving size with package size; using total fat instead of saturated fat for the 10% guideline; applying adult activity minutes to children; assuming BMI equals body fat percentage; forgetting that alcohol contributes calories.