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A new study looks at how BMI may be linked to heart health for people with type 2 diabetes. Peathegee Inc/Getty Images
  • In individuals with type 2 diabetes, researchers found that the ideal BMI to reduce the risk of death from cardiovascular disease changed with age.
  • People over the age of 65 had better health outcomes when their BMI was in the “overweight” range, compared to those whose BMI was in the “normal” range.
  • Some experts interviewed by Healthline were wary of the findings.
  • The science around BMI, obesity, and chronic disease remains controversial.

Is there a single, healthy BMI range for people with type 2 diabetes? Surprisingly, no, indicates new research, instead, a healthy BMI could change with age.

In research being presented at this year’s European Congress on Obesity (ECO) in Venice, Italy (12-15 May), scientists investigated what BMI range was most likely to reduce the risk of death from cardiovascular disease, including heart failure, stroke, and other complications of metabolic syndrome in people with type 2 diabetes. The research has not yet been published.

They found that for middle-age adults, 65 years of age and younger, a BMI of 23-25, part of the “normal” range, was associated with the lowest risk of dying from cardiovascular disease. However, for people over age 65, the optimal BMI was 26-28, which corresponds to the “overweight” range.

“Our findings suggest that there exists a disparity in the optimal cut-off point for BMI and risk of cardiovascular mortality between elderly and non-elderly individuals with diabetes. Moreover, we have identified a relatively rational range of BMI values to determine the lowest incidence of cardiovascular death among elderly and non-elderly patients with diabetes, which is imperative in this aging society,”Shaoyong Xu, MD, the lead author of the research and member of the Department of Endocrinology Xiangyang Central Hospital, Affiliated Hospital of Hubei University of Arts and Science, told Healthline.

In terms of practical implications, the research suggests that there is no “one-size-fits-all” approach to cardiovascular risk assessment in patients with diabetes. Instead, an individualized approach is more likely to yield health benefits.

To investigate the link between BMI and cardiovascular disease outcomes in individuals with type 2 diabetes, the researchers relied on data from the UK Biobank, a medical database that includes genetic, lifestyle, and health information on about a half-million individuals throughout the United Kingdom.

The study included nearly 23,000 people with baseline type 2 diabetes. Participants were predominantly white, with an average age of 59 years; about two-thirds of them were women. Individuals were enrolled between 2006 and 2010, and had an average follow-up period of 12.5 years. During this time, 891 people died from cardiovascular disease. Using BMI and age data, researchers then looked at how those factors affected mortality.

They compared two groups based on age: the elderly (older than 65) and the middle-aged (65 and under). Middle-aged adults with a BMI in the “overweight” range had a 13% increased risk of death due to cardiovascular disease. In the elderly group, they saw the opposite effect, with “overweight” individuals showing a 28% decreased risk compared to elderly participants with a “normal” BMI range.

The study also identifies an optimal BMI cut-off point at which risk of death from cardiovascular disease begins to increase. For the middle-aged group, the cut-off was 24, while the cut-off for the elderly group was 27.

“I think this adds valuable data as we need to take more than BMI into consideration when making recommendations for weight loss. The research highlights that age is important and weight loss goals need to be individualized,” Ivania Rizo, MD, an Assistant Professor of Endocrinology, and Director of Obesity Medicine at Boston Medical Center, told Healthline. She wasn’t affiliated with the research.

Other experts were more wary of drawing conclusions from the research.

“I’m left with more questions,” Sun Kim, MD, MS, an Associate Professor of Endocrinology at Stanford Medicine, told Healthline. She wasn’t affiliated with the research.

She said that while the study investigated associations between baseline BMI and cardiovascular disease, it would also be important to document how participants’ BMI changed over the follow-up period.

As to whether elderly individuals were really better off with a higher BMI, Kim is skeptical. “Does it also mean that older individuals who are normal weight should gain weight? Again, I think we need to see the limitations of this study here,” she said. Kim points out that the current guidelines from the American Diabetes Association indicate that losing any amount of weight is important.

However, she still agrees with the overarching message about the importance of individualized care:

“Some overweight individuals who are older may still benefit from weight loss if they have uncontrolled type 2 diabetes and other comorbidities with excess fat (not excess BMI). Another overweight individual with well-controlled cardiovascular risk factors, may benefit more from focusing on exercise and maintaining lean mass, which can decline with aging,” she said.

The science behind BMI, obesity, and related health outcomes has often been contentious. The BMI itself is criticized as inaccurate for not distinguishing between fat and lean muscle mass. It also doesn’t take into account race and ethnicity and is largely based on data from white men.

It is a simple, easy-to-perform, if overly general, way to assess an individual’s weight. Directly measuring body fat is more difficult, takes more time, and requires specialized equipment. Basically, it’s not something that can readily be performed during a checkup.

“BMI is a surrogate measure for body fat. It’s not practical (at this time) to measure body fat in clinical practice but it would be great if we can do that to give patients a meaningful target,” said Kim.

But there are even more controversies in the field as well. Scientists have documented that in some older individuals, those with obesity along with other chronic conditions, such as heart disease, may actually have a lower risk of death than peers with a healthy BMI. This supposedly “protective” effect of obesity is known as the “obesity survival paradox.”

“The obesity paradox is controversial. It also highlights the need to evaluate other markers such as function, fragility, waist-to-height and waist circumference to better understand a person’s risk of cardiovascular death, especially in those 65 years of age and older. These may be better markers at evaluating the risk that adiposity has on that person’s health,” said Rizo.

Other methods of measuring adiposity, such as waist-to-height ratio and waist circumference may be better than BMI, but aren’t perfect either.

Using multiple measurements together, rather than relying on them individually, undoubtedly reveals a clearer picture about not just a person’s weight, but their health in general.

“This research highlights the importance of looking at other anthropomorphic markers and not just BMI in all ages and especially those older than 65 years of age…It is important to also look at other factors such as waist circumference and waist-to-height ratio, as an upward trend in both these markers did have a positive relationship with cardiovascular events and mortality,” said Rizo.

Researchers found that the ideal BMI to reduce the risk of death from cardiovascular disease varied by age.

Elderly individuals with type 2 diabetes had better health outcomes when their weight fell in the “overweight” BMI range, compared with those whose weight was in the “normal” range.

Experts say the findings underscore the importance of individualized care and not a “one-size-fits-all” approach to cardiovascular risk assessment.

Some of the science around BMI, obesity, and health outcomes remains controversial.