Poor Metabolic Health Raises Coronary Heart Disease Risk Regardless of BMI

Challenging the concept of “metabolically healthy obesity,” a new large prospective study indicates that coronary heart disease risk is just as high, if not higher, for individuals with metabolic syndromes compared with their healthy counterparts regardless of body mass index (BMI).

Some prior studies have shown that cardiovascular risk isn’t always highest in those with excess body fat and that these patients might even be protected from heart disease, while others continue to challenge the notion that being overweight or obese can ward off adverse events. These issues are complicated by measures of overall fitness and whether fitness is defined by cardiorespiratory or metabolic factors, or by both.

To address the uncertainty felt by many physicians, Camille Lassale, PhD (Imperial College London, England), and colleagues identified 7,637 incident coronary heart disease cases among the 520,000-person European Prospective Investigation into Cancer and Nutrition (EPIC-CVD) study. Median follow-up was 12.2 years, and 15.8% were obese (BMI ≥ 30 kg/m²). To be classified as metabolically unhealthy, subjects needed to have three or more of the five classic metabolic risk factors: elevated blood pressure, hypertriglyceridemia, low HDL-cholesterol, hyperglycemia, or elevated waist circumference.

The researchers’ findings, published online August 14, 2017, in the European Heart Journal, show that compared with people who have normal weight (BMI 18.5-24.9 kg/m²) and are metabolically healthy, the risk for coronary heart disease is more than doubled for those who are overweight and metabolically “unhealthy.” Indeed, even subjects with more than two metabolic abnormalities but within the normal weight range were at increased coronary disease risk. Similarly, metabolically healthy individuals who were overweight or obese still had elevated risks of CHD compared with the reference group.

CHD Risk vs Metabolically Healthy, Normal-Weight Individuals

“Our study, which is the largest to address this question in terms of the number of incident CHD events, suggests that ‘metabolically healthy’ obesity is not a benign condition,” Lassale and colleagues write. “This is of particular importance as overweight people . . . with no traditional cardiometabolic risk factors are not recommended for weight loss treatment by recent UK or USA guidelines.”

Even when multiple traditional risk factors for cardiovascular disease are missing, “weight-loss strategies through intensive lifestyle advice (diet, exercise, and behavior modifications) or medical therapy (orlistat or bariatric surgery) should be recommended for obese patients,” they add. “Overall, these results support a population-wide strategy for prevention of obesity and overweight regardless of the initial metabolic status of individuals.”

What Exactly is Fitness?

Commenting on the study for TCTMD, Benoit Arsenault, PhD (Laval University, Québec City, Canada), pointed out that the study cannot speak to the issue of ‘fat but fit,’ since it did not measure cardiorespiratory fitness, which is not the same thing as ‘metabolic fitness.’

“It’s going to take more than a study like this to convince me” the ‘fat but fit’ concept is not a myth, he said.

Likewise, Carl ‘Chip’ Lavie, MD (John Ochsner Heart & Vascular Institute, New Orleans, LA), who was also not involved with this analysis, told TCTMD that he suspects “that the metabolically healthy and fit would have no increased risk, [but] they just studied a crude assessment of physical activity.”

Arsenault said that studies such as this one make important contributions to this field of study. Where problems can arise, he stressed, is in how these are interpreted by the lay press. He noted that the press release accompanying the paper was titled “'Fat but fit' are at increased risk of heart disease,” and that the ensuing coverage he has observed can be misinterpreted by both patients and physicians.

“The right message here should be that being lean does not mean that you are at lower risk of heart disease, . . . and having a high waist line is more of a powerful predictor than BMI,” Arsenault said. “This is not necessarily reported as much as the 'fat and fit' is a myth concept. Although the study is very nicely executed [and] it’s valid, the conclusion might be a little bit overemphasized. This message that simply having a high BMI and that we should target BMI regardless of metabolic dysfunction [is not] the right message that we should send, and I don't think that it's the message that is being carried by this paper.”

Rather than focus so much on BMI—which several other studies have now claimed to be less effective a quantifier of risk than something like waist circumference—Arsenault said that clinicians should focus more on specific behavior modification with their patients. Simply telling a patient to lose weight is “like telling somebody to lower their blood pressure but not give them a blood pressure lowering drug,” he noted.

Lifestyle changes in exercise and diet also don’t always lead to huge amounts of weight loss, so patients can get discouraged if their physicians only focus on BMI and not something like waist circumference, which may change more, Arsenault said. “You have to realize that behaviors such as physical activity and healthy eating are risk factors in themselves. So just by targeting them, by changing the way we eat and by moving more, we literally improve these risk factors and we're going to eventually improve cardiovascular outcomes regardless of body weight changes.”

Future studies should include cardiorespiratory fitness as the main measure of fitness, he suggested. Also, Arsenault said he “would like to see more cardiovascular outcomes trials [looking at] these changes in behaviors,” adding, “I would like this study to be repeated either in other countries [or] also to add a physical activity component just to quantify the amount of risk reduction that we can obtain from changing our lifestyle habits.”