Now with that being said, I want to make sure that we don’t pass the wrong message that obesity is a good thing, because if these individuals didn’t become obese in the first place, it could have likely prevented the development of cardiovascular disease. So, we still need to make all the effort we can to prevent obesity.7 But I think that one important point that has come out of these studies and a paradigm change in how we think about patients compared to 15-20 years ago, is that we should pay greater attention to heart failure patients with a normal BMI and clearly in those underweight, perhaps more than heart failure patients with class I obesity, since the former have a higher all-cause and cardiovascular mortality risk.
I believe that the obesity paradox is a real phenomenon, but we still don’t clearly understand the underlying mechanisms responsible for it, nor do we have data from large multicenter randomized controlled trials looking at targeting obesity in the setting of heart failure or other established cardiovascular disease, so we can’t say this with certainty. One hypothesis we have proposed as a group is that patients with obesity in addition to having excess body fat, typically also have excess lean mass, which is a surrogate for skeletal muscle mass.8 And we know that high lean mass is associated with improved prognosis in some cardiovascular conditions, including heart failure. So, it is plausible to think that patients with obesity may do better because they have that excess lean mass. We recently published a review article in Current Problems in Cardiology discussing the role of lean mass and different body composition phenotypes (sarcopenia, sarcopenic obesity and cachexia) in determining cardiorespiratory fitness and overall prognosis in heart failure, where we make a strong distinction between the use of BMI and body composition compartments such as lean mass.9 For example, heart failure patients with excess body fat (i.e., obesity) but a low amount of lean mass (also called sarcopenic obesity) are the ones who actually do worse and have the most impaired cardiorespiratory fitness, even if they have class I obesity, so it is important to make that distinction.