Should we care about BMI?

There has been much debate in recent years about whether this is an accurate indicator of health or not. It is certainly an important measure in scientific research and useful for predicting health outcomes for whole populations.

So, what is BMI and how did it come about?

First created in the 19^th century, BMI was a scientific measure, intended for observing population-based trends and identifying a ‘normal man’. It uses an adult’s height and weight to calculate a figure which was further developed in the 1970s to assess their long-term health risks.

Does the number matter?

A great deal of data shows unequivocally that obesity increases your chances of developing a whole host of diseases, including cancer, type 2 diabetes, dementia and cardiovascular disease. Where the data is more nuanced however, is around people in the overweight category.

An equally broad range of statistics show that being overweight but healthy doesn’t carry the same risks. So, what does ‘healthy’ mean? A good indicator is having blood fats, blood sugar and blood pressure within the ‘normal’ range and doing at least 150 minutes physical exercise a week. Even if you are carrying a little bit of extra weight, if these measures are in the expected range, it greatly decreases your likelihood of developing a chronic disease.

It’s biggest flaws

Conversely, it is possible to have a ‘normal’ BMI but be at significant risk of long-term health issues.  In fact, the term TOFI is used in medical literature to describe someone who is ‘thin outside and fat inside’. This is a situation where, although of a lighter weight, someone may be metabolically unhealthy, with levels above the normal range for the blood markers mentioned above.

Additionally, the measure is a simple one and doesn’t account for body composition. Given that muscle weighs considerably more than fat, and someone who is fit and actively building muscle may flag up as obese, highlights its limitations. So, whilst the BMI measure is here to stay for now, up to date science suggests a more accurate measure is your waist to hip ratio. You can find out more about that here: https://www.diabetes.co.uk/waist-to-hip-ratio-calculator.html

Also, bear in mind that I rarely discuss weight with my clients. My focus is always on health and fitness. Weight is simply a number and focusing on being thin too much may not ensure good health as you age.