3.4 - Body Mass Index (BMI)

Calculating and Determining BMI

• Body Mass Index (BMI) is a measure of body mass in relation to height.
• BMI helps determine whether a person has a body-mass problem.

• Unit: $\mathrm{kg}{\mathrm{m}}^{-2}$.
• Measure body mass in kilograms and height in metres, square the height, then divide body mass by the squared height.

BMI chart

BMI ($\mathrm{kg}{\mathrm{m}}^{-2}$)	Category
Below 18.5	Underweight
18.5–24.9	Ideal body mass
25.0–29.9	Overweight
30.0 or above	Obese

• The BMI chart determines whether a person is underweight, has an ideal body mass, is overweight or is obese.
• A person with an ideal BMI of 18.5–24.9 kg m⁻² has a higher life expectancy than a person with a lower or higher BMI.

Interpreting BMI and Deciding on Further Action

Risks of excessive body mass

• Heart attack
• High blood pressure
• Stroke
• Diabetes mellitus
• Joint and bone complications

Risks of being underweight

• Heart disease

• Reduced body resistance against disease

• Fatigue

• Anaemia

• Depression

• Achieving and maintaining an ideal body mass through healthy eating and consistent physical activity helps prevent these health problems.

Ways to Gain Body Mass

• Practise a healthy, balanced diet guided by the Malaysian Food Pyramid and Malaysian Healthy Plate.
• Eat at fixed times.
• Take nutrient-dense snacks to increase calorie intake.
• Eat more nutritious food than usual.

Ways to Lose Body Mass

• Set a realistic target, such as losing 0.5 kg per week.
• Monitor and record body mass once a week.
• Eat healthy food in moderation based on the Malaysian Food Pyramid and Malaysian Healthy Plate.
• Change eating practices, including food-preparation methods.
• Reduce or avoid food with high sugar or fat content.
• Perform moderate exercise such as brisk walking, cycling or swimming for at least 30 minutes, three days a week.
• Obtain support from people close to you.