From the Journals

Large study weighs in on ‘fat but fit’ paradox



Physical activity mitigated the impact of high body mass index (BMI) on cardiovascular risk factors, but not overall cardiovascular disease risk, according to an observational study of half a million individuals.

Dr. Prakash Deedwania of the University of California, San Francisco

Dr. Prakash Deedwania

Despite the historically high rates of overweight and obesity worldwide, some evidence suggests that cardiorespiratory fitness could reduce the effects of excess weight on cardiovascular disease risk, wrote Pedro L. Valenzuela, PhD, of the University of Alcalá, Madrid, and colleagues.

“To clarify the existence of the ‘fat-but-fit’ [or ‘elevated BMI but active’] paradox, in this observational study, we assessed the joint association between different BMI categories and physical activity levels, respectively, and the prevalence of major CVD risk factors,” they said.

In a population-based cohort study published in the European Journal of Preventive Cardiology, the researchers identified 527,662 adults aged 18-64 years who were insured by an occupational risk–prevention company and underwent annual medical exams as part of their coverage. The average age of the participants was 42 years, 32% were women, and the average BMI was 26.2 kg/m2.

The participants were categorized as normal weight (42%), overweight (41%), and obese (18%), and their activity levels were categorized as inactive (64%), insufficiently active (12%), and regularly active (24%). In addition, 30% had hypercholesterolemia, 15% had hypertension, and 3% had diabetes.

Overall, compared with inactivity, insufficient activity or regular activity reduced CVD risk factors within each BMI category, and subgroups. “However, regular/insufficient PA did not compensate for the negative effects of overweight/obesity, as individuals with overweight/obesity were at greater CVD risk than their peers with normal weight, irrespective of PA levels,” the researchers said. Compared with active normal-weight men, the odds ratios for hypertension in active overweight men and active obese men were 1.98 and 4.93, respectively; the odds ratios for hypercholesterolemia were 1.61 and 2.03, respectively, and the odds ratios for diabetes were 1.33 and 3.62, respectively (P < .001 for all). Trends were similar for women.

The study results were limited by the cross-sectional design; inability to control for participants’ diet, and the reliance of self-reports of leisure-time physical activity. However, the findings were strengthened by the large sample size and “refute the notion that a physically active lifestyle can completely negate the deleterious effects of overweight/obesity,” the researchers said.

Although increasing physical activity should remain a priority for health policies, “weight loss per se should remain a primary target for health policies aimed at reducing CVD risk in people with overweight/obesity,” they concluded.

Interpret findings with caution

“With the ever-increasing public health problem of overweight and obesity, it is useful to assess any measure or measures that can have a favorable or adverse effect on cardiometabolic risk factors and the risk of CVD” Prakash Deedwania, MD, of the University of California, San Francisco, said in an interview.

Dr. Deedwania said he was not entirely surprised by the study findings. “The investigators have correlated only the self-reported level of physical activity (which is not always reliable) to the presence of three cardiac risk factors: hypertension, hypercholesterolemia, and diabetes.”

The study “is not comparable to prior reports that had shown a favorable impact of carefully assessed cardiorespiratory fitness with the risk of CVD,” Dr. Deedwania noted. “However, this is one of the largest population-wide surveillance studies of more than a half million active workers across Spain, and it does show that, despite self-reported physical activity, overweight and obesity are associated with higher risks of hypertension, diabetes, and hypercholesterolemia,” he explained.

“The main message of these findings is that, although physical activity does have a dose-dependent favorable impact on CV risk, the main public health intervention to reduce the risk of CV risk should focus on weight loss in overweight and obese individuals,” Dr. Deedwania emphasized.

“Future studies should focus on comparing various levels of daily activities and routine exercise such as walking, bicycling, etc., with the beneficial impact on cardiometabolic risk factors in overweight and obese individuals,” he said.

Dr. Valenzuela disclosed support from the University of Alcalá. Research by corresponding author Dr. Lucia was funded by grants from Spanish Ministry of Science and Innovation and Fondos FEDER. Dr. Deedwania had no financial conflicts to disclose.

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