Fit but fat: The problem with BMI

On Thursday, the founder CEO of Zerodha, Nithin Kamath, tweeted: “We are running a fun health program at @zerodhaonline. Anyone on our team with BMI <25 gets half a month’s salary as bonus. The average BMI of our team is 25.3 & if we can get to <24 by August, everyone gets another ½ month as a bonus.”

In a following tweet he admitted, “I know BMI isn’t the best measure to track health & fitness, but it is the easiest way to get started. With health & most other things in life, the most important bit is to get started. Btw, walking 10,000 steps daily is a great start.”   

A healthy office is undoubtedly likely to be a more productive office. It might even mean lower insurance premiums, if the company subscribes to a corporate health insurance scheme.

Many new age offices have high-end gyms and physical trainers on call. But work from home protocols, and the pandemic that triggered those protocols, imply this might not be a safe, or even an efficient way to promote health. A large chunk of the workforce might not come to office, and a communal gym may expose people to Covid.  

Incentivising employees to stay healthy is a good idea. They can pick up treadmills, weights and yoga mats, and switch on appropriate YouTube videos and isolate at home while exercising.

However, body mass index, or BMI, is a horrible benchmark. BMI divides body weight by height and spits out a ratio, using a formula of kilograms of body weight divided by the square of the height in metres. For example, Sachin Tendulkar is 1.65 metres tall and weighed 62 kgs when he was an active cricketer. So his BMI was 22.8.

The rule of thumb is, healthy adults have BMI ratios between 19 and 25. Below 19, the person is likely underweight and above 25, the individual is edging into the overweight zone. Over 30, BMI says you’re obese and below 16.5, you’re nearing anorexia. Tendulkar was, therefore, in the middle of the “healthy” range.

But all elite boxers classify as fat, or obese, on the BMI chart. Mike Tyson in his prime, when he was beating the hell out of everyone, weighed 100 kgs. He was 1.78 metres tall. So he had a BMI of 31.5, which qualifies as “obese”. Muhammad Ali — “The Greatest” also had a BMI of 29.5 in 1965, which is “very fat”.

In 1986, when he was the world’s best footballer, Diego Maradona weighed 77 kgs and his height was 1.66 metres. Maradona was therefore “fat”, with a BMI of 28. In other athletic domains like weightlifting, discus throwing, sprinting, judo, most Olympic competitors have BMIs closer to 30 than to 25. Around a third of the National Basketball Association (NBA) and women NBA stars have BMIs above 25 and so do a lot of footballers, and volleyball players.

Muscle weighs much more than fat and many athletes are heavily muscled. Anyone who’s lifted weights with some seriousness is aware of the phenomenon where inches reduce around the waist and belly, but the weight stays the same or increases.

Tyson and Ali in their prime actually had just 7 per cent body fat, while Maradona had 10 per cent body fat. According to most elite trainers, a top athlete would be in the 7-10 per cent body fat zone. This doesn’t make them unfit — indeed, just the opposite.

By definition, the BMI has to be inaccurate if it classifies a wide range of top athletes as overweight. Using BMI as a benchmark is, therefore, dicey since it is very possible that the fittest people in an office — those who work out regularly with weights— will have BMIs above 25. This is quite apart from the fact that setting off a BMI-based competition could lead to the body-shaming of valuable employees.

A 10,000 step is indeed considered to be a healthy exercise routine. But instead of buying a Fitbit and counting footsteps, acquire a medium-sized or large dog and take it for walks. Your fitness will improve, and your blood pressure and cholesterol will also normalise as pets generally lead to lower stress levels and you’re likely to live longer.