Using scientific knowledge to reduce the risk of CHDSpec 1.19
In short
People use scientific knowledge to reduce the risk of coronary heart disease by eating less saturated fat and salt and more fruit and vegetables, taking regular exercise and not smoking. Body mass index (mass ÷ height²) and waist-to-hip ratio are indicators of obesity, which raises risk, with a high waist-to-hip ratio showing excess abdominal fat.
| Change | Scientific reason |
|---|---|
| Eat less saturated fat | Lowers LDL cholesterol, so less atheroma forms |
| Eat less salt | Lowers blood pressure, so less endothelial damage |
| Eat more fruit, vegetables and fibre | Antioxidants and fibre; helps control weight and cholesterol |
| Take regular exercise | Lowers blood pressure, raises HDL, helps control body mass |
| Stop smoking (or never start) | Removes carbon monoxide, nicotine and chemicals that damage the endothelium and raise clotting |
| Keep to a healthy body mass | Obesity is linked to high blood pressure and raised LDL |
Obesity indicators
A BMI under 18.5 is classed as underweight, 18.5 to 24.9 as healthy, 25 to 29.9 as overweight and 30 or over as obese. BMI is simple to calculate but does not distinguish muscle from fat, so a muscular person can have a high BMI without being unhealthily fat. Waist-to-hip ratio shows fat distribution: a high ratio means more fat stored around the abdomen, which is linked to a higher risk of CVD (commonly used thresholds for higher risk are above 0.90 in men and above 0.85 in women).
Calculating BMI and waist-to-hip ratio
A man has a mass of 80 kg and a height of 1.75 m. His waist is 92 cm and his hips are 102 cm. Calculate his BMI and waist-to-hip ratio.
- BMI = 80 ÷ 1.75² = 80 ÷ 3.0625 = 26.1 (to 3 s.f.)
- Waist-to-hip ratio = 92 ÷ 102 = 0.90 (to 2 d.p.)
Answer: BMI 26.1 kg m⁻² (overweight); waist-to-hip ratio 0.90
Square the height before dividing in BMI, and use the same units for waist and hip. BMI is expressed in kg m⁻² and waist-to-hip ratio has no units.
Written and checked against the Edexcel International AS Level Biology (XBI11) specification · Updated October 2026