It's probably time to ditch BMI tests, nutritionists advise ministry

Most health-conscious Kenyans are no strangers to the body mass index, currently the gold standard to diagnose obesity.

However, leading nutritionists are urging the government to stop the obsession with BMI as it is no longer a reliable indicator of who is obese and who is not.

The nutritionists said thousands of Kenyans who are classified as healthy through BMI are actually obese.

This means many people do not actively take steps to prevent obesity-related diseases such as diabetes, believing they are healthy.

There are also many “obese” Kenyans who are actually healthy because their weight is in the muscles or fat is packed in harmless places such as the buttocks.

Dr Dorcas Mbithe from Kenyatta University and Dr Zipporah Ndung’u (Jomo Kenyatta University of Agriculture and Technology) observed large differences between who was obese or not depending on the measure applied to about 100 women who took part in their study in Nyeri last year.

While using BMI, only 23 per cent of the women were obese, but that jumped to 46 per cent if the nutritionists used atomic precision to measure body fat.

“BMI is leaving out many people and whatever is happening inside of them is very different from what we can see,” Dr Ndung’u said.

She noted that many Kenyans who could benefit from interventions to prevent obesity-related diseases do not.

“BMI severely underestimates body fat and that can be a challenge because we use BMI for intervention. So this means we are not addressing all individuals that we should be addressing,” she said.

“We also had many classified as overweight with BMI but with normal body fat composition.”

The two experts spoke at the two-day annual national nutritional conference organised by the Ministry of Health, which began on Wednesday in Nairobi.

Calls to adopt other measures of body composition are not new, but BMI sticks around because it is cheap to carry out and easy to calculate.

It is simply calculated by dividing your weight in kilogrammes by height in metres squared.

It was developed nearly 200 years ago by a Belgian mathematician to create a description of the “average person” and therefore help the government estimate obesity numbers in the general population.

The result classifies you into one of four categories: underweight (BMI of less than 18.5), normal (between 18.5 to 24.9), overweight (25.0 to 29.9), and obese (BMI of 30 and above).

The 2015 World Health Organisation’s Kenya STEPwise Survey was the first nationally representative survey to objectively measure BMI in Kenya.

The survey examined 4,340 adults aged 18 to 69. The mean BMI was 23.51 with 31.13 per cent of Kenyans being overweight or obese.

While the JKUAT and KU experts did not dispute the StepWise or other past studies done in Kenya, they noted BMI misses important factors such as family history, genetics, lifestyle, age, sex, fat distribution and muscle mass when considering a person's overall health and their risks of developing diseases.

Obesity is defined as an excessive accumulation of fat that presents a risk to health.

However, BMI does not measure body fat or distribution.

Yet excess fat around the internal organs has more health consequences than distribution around the buttocks.

Dr Mbithe said they used one of the atomic precision techniques to measure body fat composition in participants of their study in Nyeri.

Atomic precision techniques can determine the percentage of body fat with high accuracy.

An international panel of experts—known as the Lancet Commission for diagnostic criteria for clinical obesity—is currently assessing the use of BMI and finding new ways to diagnose obesity.

Dr Mbithe also noted Kenya lacks an obesity policy.

“Being overweight or obese sets the stage for non-communicable diseases. We don’t have guidelines for managing overweight and obesity,” she said.

She also said many obese people have already made peace with their bodies, or given up on weight management, despite the risks.

“Half of the obese women in our study refused weight reduction. It's called ‘learnt helplessness’ because of past failed attempts,” she said.

-Edited by SKanyara