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Is obesity always bad for chronic disease?

Today’s debate on the ‘unexpected’ paradox of obesity: ESC Congress News 2015 - London

Prevention


No says Wolfram Doehner, Charité - Universitätsmedizin, Berlin, Germany

Obesity, clearly, is an ever growing health burden to our society. The world report on burdens of disease ranks obesity among the top ten in a list of 67 risk factors - even moving from 10th to 6th between 1990 and 2010. Consequently, weight reduction is unanimously advocated by healthcare providers. In fact, there can rarely be a piece of healthcare advice that has not been more rigorously implanted in the public consciousness than weight loss as a benefit for all.     

However, it needs to be made clear that such unqualified recommendation (which often enough is pursued as plain starvation) may not always be in the best interest. For example, no-one would recommend a cancer patient to go on a weight-reducing diet. More unexpectedly, and even in many cardiovascular conditions, a significant survival advantage can be seen with overweight - and, in turn, weight loss predicts an increased mortality risk, regardless of whether this happens intentionally or not.   

In fact, the association between body weight and survival follows a U-shaped curve, with an optimum body weight for healthy and middle-aged populations somewhere around a BMI of 25 kg/m2, with the risk steadily increasing with both higher and lower body weights. While this point already marks the boundary between normal weight and overweight according to the WHO categories, a significant increase in mortality is observed with lower body weight throughout the ‘normal BMI’ range (18.5-25 kg/m2).    

It thus may easily be understood that the nadir of this body weight-mortality association and the slope of the U-shaped curve may be different in different health conditions. Two specific conditions are highly important here, as we see them regularly in our clinics and hospitals: patients with established cardiovascular diseases and subjects who are old. In such cases, the optimum body weight with regard to mortality is shifted significantly towards the overweight and even mildly obese range.   

This is, of course, counterintuitive to the wisdom of obesity as risk factor in healthy subjects (ie, in primary prevention). Accordingly, an ‘obesity paradox’ has been termed to reflect a finding which was a) unexpected and b) difficult to explain. Over the last 15 years, however, substantial evidence has accumulated to confirm a survival advantage with higher body weight in several CV diseases. In fact, in almost every cardiovascular disease or condition which was examined for this association, a higher body weight was found to predict better outcome. Indeed, in patients with heart failure, the survival benefit of higher body weight was even implemented in validated risk score calculators.     

So the question we need to ask ourselves should be: If the inverse association of higher body weight with improved survival has been confirmed in a wide range of CV diseases, and in numerous cohorts with various disease severities and co-morbidities, and assessed by different methods, why would this still be considered an unexpected and contradictory - indeed a paradoxical - finding?     

It should be the time to consider moving from a cardiovascular obesity ‘paradox’ to an obesity ‘paradigm’ to appreciate this clinical observation.  The available evidence strongly suggests that overweight and obesity are not always bad, and may in fact carry some protective signal in many cardiovascular conditions. It will be the challenge for us to convince both professional and public opinion to adopt weight management recommendations that clearly distinguish between healthy subjects (to avoid overweight and obesity) and patients with established disease (where being overweight may carry some benefit and weight loss indicates disease progression and worse prognosis).     

In any case, as a physician and scientist making decisions based on evidence and reasoning, one needs to appreciate that ‘obesity is not always bad’.  

Yes says Dan Gaita, Institutul de Boli Cardiovasculare, Timisoara, Romania

We are in the midst of an obesity epidemic which has an impact on hundreds of millions of people around the world. Obesity has mental, physical and social implications because of its link to a vast multitude of pathological consequences. And importantly, obesity bears a significant cost for individuals, employers, healthcare systems and nationally economies.

Obesity and overweight are chronic conditions resulting from positive energy balance over time - with causes related to a combination of factors which vary from one person to another, including individual behaviours, environmental factors and genetics, which all contribute to the complexity of this disorder.      

However, from an evolutionary point of view, maintaining modest excess body weight has served as an adaptive mechanism, protecting individuals by storing excess energy into fat cells during periods of food abundance.     

Importantly, the negative effects of excess weight on mortality and morbidity have been recognised for more than 2000 years, although not with the name of ‘atherosclerosis’. Indeed, it was Hippocrates who noted that ‘sudden death is more common in those who are naturally fat than  lean’!  

There remains debate whether increased BMI, an estimative indicator calculated using the weight and height of an individual, is a reliable indicator of increased vascular risk. Thus, while trying to define ‘normal’ weight, we should also consider factors such as the dichotomy of young versus old and healthy versus ill when examining obesity as a risk factor for cardiovascular disease (eg, metabolism is slowing down about 2-5% per decade after age 40).   

One could reasonably argue about the most predictive metabolic markers of increasing  cardiovascular risk in the obese and overweight. There are data related to traditional risk factors such as waist circumference, percentage body fat, cholesterol and triglyceride levels, elevated blood pressure, insulin resistance, or others such as inflammatory markers. Ongoing investigation is focused on identifying predictive measures in order to better recognise risk related to obesity.        

One much debated question is who is better off from a risk point of view - one who is fit and fat or a lean couch potato? There is evidence that unfit men in the BMI range of less than 25 kg/m2 have a significantly higher risk than men with a high level of cardiovascular fitness - while on the other hand, overweight men with a high level of fitness have a risk of death which is not very different from that of fit men with normal body fat. It is critical to recognise, however, that the lowest cardiovascular risk is seen in those with normal bodyweight associated with a high level of fitness.  

There is some evidence to suggest that individuals with normal blood levels of inflammatory markers are more likely to have favourable ‘metabolic health’ whether they are lean or obese – which means that up to 35% of obese individuals may be metabolically healthy despite their size, although the true prevalence of ‘healthy obesity’ is difficult to assess due to a lack of clarity in defining metabolic health.    

Lastly, there is a central question to be raised. Are there truly healthy obese individuals or are ‘metabolically healthy obese’ persons on a temporary ‘normal’ stage or on an imminent path towards disease, including the major threats to modern humanity, diabetes and atherosclerosis.  

As a physician one must continue to support the position that ‘obesity is always bad’.

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Is obesity always bad? 29 Aug 13.30-15.00 Moscow - Village 2