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When it comes to determining whether a person is overweight, body mass index (BMI) is the most widely used measure out there. But doctors admit that BMI�a ratio of weight to height—is far from perfect. Now, a new study suggests there may be a better way to estimate the risks of health problems associated with excess weight.

A nova pesquisa, publicada hoje no Annals of Internal Medicine, achar algo relação cintura-quadril was a better predictor of whether people would die over the course of the study, compared to BMI. This isn’t the first study to reach esta conclusão, mas é um dos maiores até hoje.

Pesquisadores da Universidade de Loughborough no Reino Unido e da Universidade de Sydney na Austrália analisaram dados de homens e mulheres 42,702 que vivem na Inglaterra e na Escócia durante um período de 10. Especificamente, eles queriam saber se as pessoas que carregavam peso extra em torno de seus medicamentos estavam em maior risco de problemas de saúde, em comparação com aqueles que eram tecnicamente com excesso de peso, mas carregavam seus quilos extras em outros lugares.

Ao longo do estudo, 5,355 dos participantes morreu. Depois de controlar fatores como idade, gênero, fumador status, and physical activity, the researchers found that people who had normal BMIs but who also had “central obesity”—defined as a high waist-to-hip ratio—had a 22% increased risk of death from all causes, compared to people with normal BMIs and healthier waist-to-hip ratios.

As pessoas obesas com obesidade central também apresentaram maior risco de morte em comparação com indivíduos com peso normal e cintura normal.

On the other hand, people who were technically overweight or obese based on their BMIs—but who did não have central obesity—were less likely to die than people with normal BMIs but high waist-to-hip ratios.

Surpreendentemente, pessoas obesas com obesidade central não have an increased risk of death from all causes, compared to people with a normal weight and smaller waistlines. These findings are counterintuitive, say the authors, but they’re similar to those of previous research: A 2015 study found that people with normal BMIs but central obesity had the piores taxas de sobrevivência a longo prazo, mesmo quando comparado com pessoas com excesso de peso e obesas que também tiveram obesidade central.

Explaining these “paradoxical findings” is challenging, the authors say. One possibility is that overweight and obese people are more likely to also have extra fat stored around their legs and hips, which has been linked to healthier metabolism.

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The authors also say that limitations in their research—like the fact that BMI and waist measurements were only collected once, rather than several times over the course of the study—may have skewed the results.

Mas eles ressaltam que todos os Os participantes com obesidade central, em cada grupo de IMC, estavam em maior risco de morrer especificamente de doença cardiovascular. Isso pode implicar que os riscos para a saúde do excesso de gordura da barriga estão especificamente relacionados a problemas cardíacos, dizem os autores, mais do que outras causas importantes de morte.

Pessoas com IMC entre 18.5 e 25 são consideradas como peso normal; entre 25 e 30 é considerado excesso de peso, enquanto 30 e superior é obeso. A obesidade central é definida como uma relação cintura-quadril de 0.85 ou superior para mulheres e 0.9 ou superior para homens. (Here’s how you can calculate both.)

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O autor principal Emmanuel Stamatakis, PhD, professor associado de saúde pública na Universidade de Sydney, says that while BMI has its flaws, it does provide some useful information—especially for tracking general trends in large groups of people over time.

“Instead of ditching BMI and replacing it with waist-to-hip ratio, which is relatively easy to measure and is consistently associado à saúde cardiovascular and mortality risk, we should be thinking about adding waist and hip measurements into routine medical examinations and in health studies,” Stamatakis told Saúde via e-mail.

But Stamatakis says that, on an individual basis, waist measurement might be more important for overall health. “If I had to choose between making sure my BMI or my waist-to-hip ratio are OK, I would go for the latter,” he says.

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BMI can be affected by many things, he says, including the amount of lean muscle mass a person has. (That’s why super-fit people, especially men, can register as overweight based on BMI alone.)

A high waist-to-hip ratio, on the other hand, most likely means high amounts of abdominal fat—which has been definitively linked to serious health risks.

“People with larger waistlines may want to start thinking and, if needed, seek help to alter their lifestyle to reduzir a gordura da barriga,” says Stamatakis. “Increasing physical activity, improving diet, and cutting down on alcohol consumption can work miracles if sustained in the long term, and all have a myriad other co-benefits in terms of health and wellbeing.”