BMI and when obesity treatment is appropriate

BMI is a single number derived from your weight and height. It is useful and it is crude, and most pages tell you only the first half of that. You can work yours out with the BMI calculator.

How it is calculated

Weight in kilograms divided by height in metres squared. Someone who is 90 kg and 175 cm has a BMI of about 29.4. There is nothing more to it: it is a ratio, not a measurement of fat.

Why doctors use it anyway

Because it is quick, free, and across a population it tracks the risks associated with excess weight reasonably well. When a doctor needs somewhere to start, BMI is a sensible start. It opens the conversation; it does not close it.

What BMI cannot see

It cannot tell muscle from fat. An endurance athlete can read as "overweight" and be metabolically fine. It does not know where the fat is, although fat around the abdomen carries more risk than fat elsewhere. And it knows nothing about your blood pressure, your blood sugar, your liver, your sleep, or how you feel.

That is why a doctor also looks at waist measurement, blood work, the conditions you have, the medicines you take, and what you have already tried.

There is no number that means you qualify

This matters, and it cuts against what you will read elsewhere. No BMI threshold automatically means something will be prescribed to you, and no number automatically means it will not. A doctor decides after looking at the whole picture, including the possibility that treatment is not appropriate and something else should be addressed.

If a site tells you "with a BMI over X we will prescribe you Y", it is promising something it does not decide.

So what should you do with the number

Treat it as one reading among several. If it is high, that is a reason to talk to a doctor, not a diagnosis. If it is normal and you are still struggling, that is also a reason to talk to a doctor, because a normal BMI does not rule out metabolic problems.

a.clinic is a technology platform. Healthcare is provided by a licensed doctor, who decides whether any treatment is appropriate for you. We do not decide about specific medicines and do not write about them.

What BMI counts as obesity?

The commonly used bands are overweight from 25 and obesity from 30, but these are population categories, not an individual diagnosis. What they mean in your case is for a doctor to judge alongside everything else.

My BMI is high. Does that mean I will get treatment?

Not automatically. BMI is one input. A doctor also weighs your conditions, your medicines, your blood work and what you have already tried, and may decide treatment is not appropriate.

My BMI is normal but I am struggling. Is a consultation worth it?

Yes. A normal BMI does not rule out metabolic difficulty or an unfavourable distribution of body fat. A doctor looks at more than one number.

Is BMI reliable for athletes?

It tends to mislead for people carrying a lot of muscle, because muscle weighs more than fat. That is exactly why a body composition scan is done: it separates the two.