Overweight and obesity correlate with increased risk for developing various chronic diseases, such as diabetes, hypertension, cardiovascular diseases, cancer, sleep apnoea, or even deaths. Body Mass Index (BMI) and body fat percentage are commonly used to measure individual’s weight status and body composition.


Body Mass Index (BMI)

BMI is an indicator of relative weight to height. It is a predictor of health risk:

BMI= Weight (kg)/ Height (m)2

Individuals with higher BMI have an increased risk of obesity related health conditions.
Please see below the reference range for the adult population:

 BMI Asian, Caribbean, African Caucasian
Underweight <18.5  <18.5
Normal  18.5 - 22.9 18.5 - 28.9
Overweight 23.0 - 24.9 25.0 - 29.9
Obese ≥25.0  ≥30.0  

* References from Hong Kong Dietitians Association and Department of Health

People who are not within the normal BMI category, and would like to know their ideal
body weight may simply use the formula below:

Ideal body weight = Height (m)2 X 18.5 to 22.9 (for Asians) or 18.5 to 24.9 (for Caucasians)

For example: Peter is British and is 1.78m tall. His BMI is 32, so he is categorised as obese and the ideal body weight for Peter will be:

Lower limit of ideal body weight = 1.782 X 18.5 = 58.6kg

Upper limit of ideal body weight = 1.782 X 24.9 = 78.9kg

It is ideal that Peter should weight between 58.6kg and 78.9kg.


  • If the BMI is above normal, a weight loss programme is recommended to reduce the risk of comorbidities associated with obesity.
  • If the BMI is below normal, one is recommended to increase weight or, if the condition is not too severe, to prevent further weight loss.
  • People with low body weight tend to be more susceptible to infection as they may have weaker immune systems. Low body weight can also cause other health complications, such as amenorrhea in women or osteoporosis.
  • In addition, being severely underweight can also indicate other underlying diseases, which, if not treated early, can become life-threatening.

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Body Fat Percentage

There is an limitation of BMI as it does not distinguish between body fat and lean tissues. Body fat can be measured by taking a Bioelectrical Impedance Analysis (BIA). It is a reliable, and quick measurement of body components (total body water, body fat mass, muscle mass and mineral mass). Measurement of body compartments are obtained through a small alternating current applied to the body to detect the level of water and level of electric resistance.

Body Fat

Below is the glossary of the measurements:

  • BMI
    Body mass index
  • Basal Metabolic Rate
    This is the basic energy requirement to carry out basic body functions. It does not take into account the energy needed for daily activity.
  • Body Fat Mass
    The total body fat weight
  • Percent Body Fat (PBF)
    When fat mass is divided by the total body weight, the fat percentage is obtained. Usually the percentage of fat in women is higher than that in men. Below are the reference ranges of body fat percentage recommended for men and women in different age groups:
    Age Men Women
    18 - 29 years 14 - 20% 17 - 24%
    >30 yesrs 17 - 23% 20 - 27%
  • Total Body Water
    Total Body water is the amount of water in the body
  • Visceral Fat Level
    It is the rating of central obesity, that is, the fat stored within the abdominal cavity that wraps around the vital internal organs. A high visceral fat level is associated with a higher risk for heart disease, diabetes, stroke, high cholesterol, fatty liver and certain cancers.

Important note: BIA should not be done during pregnancy or on people with pacemakers.


  • If the body fat percentage is within the reference range of a specific age group, congratulations! Maintain this with a healthy, balanced diet and regular physical activities.
  • If the body fat percentage is above the reference range of a specific age group, the person is suggested to attain a healthy weight through weight management and increase the activity level to enhance muscle mass and burn off the extra fat.
  • Certain level of body fat is needed to maintain our body functions. Fat is a storage form of energy. It is needed to produce hormones and digestive enzymes and acts as a medium for absorption of fatsoluble vitamins. It protects the vital organs and keeps us insulated and maintains our body temperature. Therefore, extremely low body fat percentage does not necessarily mean healthy. Nonetheless, elite sportsman or people who are physically-active may have higher muscle mass and relatively lower body fat percentage.
  • Waist – Hip Ratio indicates if a person has central obesity or excessive abdominal fat, which is a health risk indicator. The risks include diabetes and cardiovascular disease, among others. This is used in conjunction with BMI and Body Fat Percentage to assess an individual’s health risk. For more information, check out Waist Measurements for Central Obesity.

exercise bicycle in park

To book an appointment with our dietitian, please contact the Outpatient Department at Matilda International Hospital, at 2849 1500, or This email address is being protected from spambots. You need JavaScript enabled to view it..

Articles on this website are informative only and not intended to be a substitute for professional medical advice, diagnosis or treatment. They should not be relied upon for specific medical advice.

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