Analysis adds to evidence of an ‘obesity paradox’ in heart failure

Evidence published in BMJ Heart last month supports the idea of an “obesity paradox” in heart failure (HF), further complicating a long-running debate as to whether extra weight can be cardioprotective in patients with established CVD.

The study, spearheaded by HF physician and University of Adelaide PhD candidate Michael Stokes, scrutinized the relationship between BMI, HF status and weight loss in 375,056 patients pulled from nine unique studies. In a statement, Stokes said there are some 14 new admissions for HF in South Australia every day, and up to 30% of those patients will be readmitted for heart problems within one month. It’s also a pricey prognosis with a survival rate lower than that of many common cancers.

Stokes noted obesity is a “significant contributor” to the HF burden in Australia, as it is in most places. Weight is a universal risk factor for heart disease, and while we’re aware that losing weight and maintaining a healthy BMI can help ward off CVD, we don’t know much about HF outcomes in those who are already severely overweight.

Stokes’ team reported that an obesity paradox—the idea that people who are obese fare better in terms of CVD outcomes and survival than their non-overweight peers—was clear in their analysis of HF patients. However, patients in the overweight group saw the lowest odds of CV mortality: a 14% reduced risk compared to underweight or normal-weight people.

Intentional weight loss via bariatric surgery in obese patients without established HF, atrial fibrillation or coronary artery disease was linked to an improvement in left ventricular diastolic function and reductions in left ventricular mass and left atrial size.

“In this meta-analysis, the data found a ‘U-shaped’ survival curve with the lowest mortality in overweight patients and a reduced mortality in the obese when compared with normal or underweight HF patients,” Stokes said. “There are a number of possible explanations for obesity paradox in HF, including whether obese patients are diagnosed earlier in their disease course due to greater functional impairment and also whether obese patients tolerate disease-modifying and prognostic medications compared with non-obese patients.”

Stokes et al.’s findings aren’t a far cry from the results of similar a 2018 study, which found that acute HF patients with a BMI of 23 or higher saw better survival over three years of follow-up than patients with lower BMIs. Heavier patients who were metabolically healthy saw the best survival—79.4%—of the study population, but even those with risk factors like hypertension and high cholesterol achieved 66.5% survival.

Other studies have challenged the idea of an obesity paradox, arguing that current studies don’t take into account the age, onset and duration of CVD. One expert said that limits those studies’ ability to account for the proportion of a patient’s life lived with CVD morbidity, whether they’re obese, overweight or normal weight.

“This meta-analysis adds to the body of evidence supporting the clear link between obesity and HF, the effect of weight on prognosis of HF and the impact of weight loss on cardiac remodeling,” Stokes said. “We are now conducting a randomized controlled study assessing the impact of intentional weight loss (achieved through dietary intervention and prescribed exercise) in an HF population of obese patients. This will hopefully address the important clinical question of whether intentional weight loss is beneficial in this growing group of patients."

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