When categorising adults according to their BMI and prescribing targets, we do not consider age or gender. However, for Asians, there are a bit different targets. Below link will give you an idea about that.
https://tieuduongcardiff.com//filem...andasianamericanadults-horizontal-en-2015.pdf
But, when we calculate BMI for young people, it is necessary to include age and gender for the calculation as those variables can affect the rate of growth.
For such a population, to calculate BMI, you can use the link below.
https://www.cdc.gov/healthyweight/bmi/calculator.html
But regarding targets and cutoff values, I don't know the availability of adequately validated values for Sri Lanka as I deal with adult patients only.
BMI is just one method of assessing obesity or body composition, which we use as a surrogate marker. But it has few downfalls as it does not give accurate assessment of infants, young children, bodybuilders and patients with critical illness or patients with body swelling.
For adults,
In addition, you can use waist circumference values ( For Asia, <90cm for men and <80 I'm for women)
Then subcutaneous fat assessment by skinfold thickness.
For the most accurate body composition measures, you need DEXA assessment.
But Bioelectric impedance also gives comparatively precise measurements.
To assess BIA, you can simply use Scale with BIA, or even the latest Samsung smartwatch has that feature
But I'm not sure about the accuracy of the watch. But according to Samsung, it is pretty accurate.
Body composition assays are helpful in calculating the composition of lean mass and fat separately and accurately. Not only overall body fat, can assess visceral fat too.
So it can be use in body builders or patients with critical illness with body swelling with a good accuracy.
P.S. Other methods of assessing body composition are
MRI or nuclear magnetic resonance imaging
Isotopic measurement of body water
Water air displacement based measures
