The obesity paradox: What we know and what we don’t
| Setting | Established study findings | Current limitations | Research questions |
|---|---|---|---|
| Patients with heart failure | BMI appears to be protective predominantly in patients with low fitness. | Different obesity classes have not been specifically evaluated. No separate evaluation of patients with either preserved or mid-range ejection fraction; they are largely grouped with reduced ejection fraction. | Is cardiorespiratory fitness an obesity paradox modifier in specific classes of obesity? Is cardiorespiratory fitness an obesity paradox modifier in HFpEF and HFmrEF? |
| Heart failure prevention | Improving cardiorespiratory fitness may be more important for risk reduction than lowering BMI. In patients with established diabetes, improved fitness may decrease the risk of developing HFpEF. Increasing BMI and specific measures of adiposity correlate with increased risk of developing heart failure. Even small amounts of physical activity decrease risk of developing heart failure. Physical activity appears to have a dose-dependent effect on heart failure risk, with the lowest risk associated with highest frequency of physical activity. | No differentiation between types or duration of physical activity. Limited specificity of type of heart failure as end point (ie, HFpEF, HFmrEF, or HFrEF). Women underrepresented. | What type of physical activity leads to the lowest risk of heart failure development? How do BMI and cardiorespiratory fitness (and interventions) affect development of different types of heart failure? Are findings relevant for women? |
| Weight loss | Either surgical or lifestyle-based weight loss may reduce morbidity from heart failure. Unintentional weight loss indicates acute illness and contributes to poor metabolic reserve, leading to worse outcomes. | Lack of clinical outcomes data after intentional weight loss for patients with heart failure and obesity. Limited data on specific exercise training programs in heart failure outcomes or prevention. | How does medical vs surgical weight loss affect heart failure morbidity and mortality rates, particularly with newer medical therapies for obesity? How does supervised exercise for patients with heart failure and obesity affect fitness, weight loss, and outcomes? |
BMI = body mass index; HFmrEF = heart failure with mid-range ejection fraction; HFpEF = heart failure with preserved ejection fraction; HFrEF = heart failure with reduced ejection fraction