Pathophysiology
P-II-26. Methods to define nutritional status
栄養状態の評価法とその長所・短所
BMI (Body Mass Index)
- Used to estimate obesity; BMI = kg/m²
- Limitation: does not distinguish muscle vs fat (depends on muscle mass)
| Category | BMI (kg/m²) |
|---|---|
| Underweight | < 18.5 |
| Normal | 18.5 – 24.9 |
| Overweight | 25 – 29.9 |
| Grade I obesity | 30 – 34.9 |
| Grade II obesity | 35 – 40 |
| Grade III obesity | > 40 |
Abdominal (Waist) Circumference
- Indicator of abdominal fat mass → shows fat distribution
- Measured at the midpoint between the superior anterior iliac spine and the lower rib cage (~2 cm above navel), after exhalation, abdominal wall relaxed, non-flexible tape parallel to floor
| Risk | Men | Women |
|---|---|---|
| Normal | 78–94 cm | 64–80 cm |
| Overweight (elevated) | 94–102 cm | 80–88 cm |
| Obese (high risk) | > 102 cm | > 88 cm |
Waist–Hip Ratio (WHR)
- WHR = waist circumference / hip circumference (hip measured at level of large buttock)
- Waist circumference used more frequently than WHR (because of WHR limits)
- High WHR: men > 1, women > 0.8
Other Methods
- Broca index (ideal body weight) = (height cm − 100) × 0.85
- Caliper → measures skinfolds (correlate with body fat): triceps, biceps, supra-iliac, subscapular
一問一答
▶How is body mass index (BMI) calculated?
BMI = body weight in kilograms divided by height in metres squared (kg/m²).
▶What is the main limitation of BMI as a nutritional measure?
It does not distinguish muscle from fat, so it can misclassify muscular individuals as overweight.
▶What BMI range defines normal weight?
18.5–24.9 kg/m².
▶What BMI defines overweight and obesity?
Overweight is 25–29.9 kg/m²; obesity is ≥30 kg/m² (grade I 30–34.9, grade II 35–40, grade III >40).
▶What BMI value defines underweight?
A BMI below 18.5 kg/m².
▶What does waist (abdominal) circumference indicate?
Abdominal fat mass, reflecting fat distribution and central (visceral) obesity.
▶Where is waist circumference measured?
At the midpoint between the superior anterior iliac spine and the lower rib cage (about 2 cm above the navel), after exhalation, with a non-elastic tape parallel to the floor.
▶What waist circumference indicates high (obese) risk in men and women?
Greater than 102 cm in men and greater than 88 cm in women.
▶How is the waist–hip ratio (WHR) calculated?
Waist circumference divided by hip circumference (hip measured at the level of the largest part of the buttocks).
▶What WHR values indicate high risk in men and women?
Greater than 1 in men and greater than 0.8 in women.
▶Why is waist circumference used more often than the waist–hip ratio?
WHR has limitations, so waist circumference is a simpler, more reliable single measure of central fat.
▶How is the Broca index used to estimate ideal body weight?
Ideal body weight = (height in cm − 100) × 0.85.
▶What does a skinfold caliper measure, and at which sites?
It measures skinfold thickness (correlating with body fat) at the triceps, biceps, supra-iliac, and subscapular sites.
▶Why is central (abdominal) obesity more clinically important than peripheral fat?
Visceral abdominal fat is more strongly linked to metabolic and cardiovascular disease risk.
▶Why might an athlete with high muscle mass have a misleadingly high BMI?
Because BMI counts all body weight; muscle is denser/heavier than fat, raising BMI without excess fat.
▶What waist circumference range is considered normal in men and women?
About 78–94 cm in men and 64–80 cm in women.
▶Why measure waist circumference after exhalation with the abdomen relaxed?
To standardize the measurement and avoid falsely altering it by breath-holding or muscle tensing.
▶Why is no single anthropometric measure sufficient to define nutritional status?
Each (BMI, waist, WHR, skinfolds) has limitations, so combining measures gives a more accurate assessment of fat amount and distribution.
▶What BMI range defines grade III (severe) obesity?
A BMI greater than 40 kg/m².
▶What is the advantage of skinfold measurements over BMI?
They directly estimate subcutaneous body fat rather than total weight, distinguishing fat from muscle.