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Life insurance companies are using a flawed measure of assessing body fatness as the basis for charging many customers higher premiums, Massey health researchers say.

Dr Steve Stannard, an expert in human body com position, has examined the use of Body Mass Index (BMI) as an indicator of future health on behalf of Institute of Food, Nutrition and Human Health colleague Matthew Barnes.

Mr Barnes, manager of the human performance laboratory at the University’s Palmerston North campus, had applied for a new life insurance policy but faced a high premium due to his BMI of 36. His insurance company, ING, had rated him as obese, he says, even though he had completed blood screening tests showing he was healthy and was a confirmed fitness enthusiast. The insurance company rejected Mr Barnes explanation that his BMI was due to muscle mass from lifting weights, the decision adding $8 to his monthly premium.

“A person’s BMI is calculated as their weight in kilograms divided by the square of their height in metres,” Dr Stannard says. “Population statistics show that if a person has a BMI of 26 or more their chances of developing conditions related to excessive body fat, including diabetes and cardiovascular disease, are greater than those with a BMI between 20 and 25. 

“However, BMI is not a tool to diagnose individual health status, rather it was developed to broadly describe populations for statistical use. Despite this, all the major insurance companies use BMI. Where Matt Barnes has come unstuck is that the extra weight he carries is muscle, not fat.”

TV programme Fair Go investigated the case and found that most major insurance companies used BMI.

ING agreed it would instate the normal premium for a healthy person if Mr Barnes could show that his body fat was below 25 percent. Fortunately, Dr Stannard is working with Professor Chris Cunningham, director of the University’s Research Centre for Maori Health and Development, Te Pumanawa Hauora. They are currently conducting research on the body composition of young Maori men using a custom-built underwater weighing tank. Mr Barnes was measured by PhD student Isaac Warbrick and Professor Cunningham.

“Underwater weighing is the gold standard for measuring a person’s percentage body fat,” Professor Cunningham says. “It relies on the Archimedes principle which states that the mass that a person loses when submerged in water is directly proportional to their body volume – thus the underwater tank simply measures their volume. We can then measure their body weight using conventional scales and weight divided by volume gives us density. Once we know body density, from very good published data describing the body’s fat and non-fat tissue density, we can calculate the percentage body fat.”

Mr Barnes body fat was calculated to be 22%, and, after discussions with ING, he is paying a reduced premium.

“Matt is fortunate in that as a science graduate and a University staff member he had both the knowledge and the environment where he was able to question the process the insurance company had in place,” Dr Stannard says. “It is likely that there’s quite a few people out there who are paying higher premiums than they otherwise should, and in reverse others who are paying less than they should because of the misplaced reliance the insurance industry has on BMI as a tool for medical diagnosis.”