Genetic tests for obesity risk fall short compared to BMI

A woman uses a measuring tape to measure her waist

Genetic tests for obesity risk fall short of being able to accurately predict whether a person will gain weight over 25 years, and current BMI is a better judge of how someone’s metabolic health will develop, according to a new study.

A new look into the way that we diagnose and predict people’s risk of becoming overweight suggests that we should return to an older method.

In recent years, genetic factors have become increasingly relied upon when looking at someone’s metabolic health; if a patient’s parents are, or were, overweight or obese, then the patient’s chances of gaining weight are higher.

An investigation published in JAMA Cardiology found that focusing on these genetic tests for obesity risk is not the most reliable method to predict someone’s future metabolic health.

The question the researchers asked themselves was “What is the added value of [genetic tests] in predicting body mass index over time?”

Looking at measures from 2,500 young adults, they found that calculating BMI and current fitness levels is a more reliable way to predict someone’s BMI 25 years later. Analysis of the data revealed an individual’s baseline BMI during young adulthood could explain 52.3% of an individual’s BMI 25 years later. Genetics showed a weaker association accounting for only 13.6% of a person’s midlife BMI.

Lead author on the study, Associate Professor Venkatesh Murthy reportedly said: “We found fitness is a better predictor than genetics of where your BMI will go over time… Genetics clearly has some influence, but other factors are stronger.

“There’s been a lot of attention to the idea of using genetic information to understand your risk of obesity or being overweight, and for potential drug development to address those genetic risks,” Murthy explained. “It turns out, our standard clinical exam, including an assessment of BMI, actually has vastly more information to help guide patient care.”

BMI itself is often criticised for not taking body fat percentage or age into account. However, according to this research, it may still offer better guidance than delving into each person’s genetic makeup.

In conclusion, the research team write “Caution should be exercised in the widespread use of polygenic risk for obesity prevention in adults, and close clinical surveillance and fitness may have prime role in limiting the adverse consequences of elevated BMI on health.

The research was published in JAMA Cardiology.

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