To many readers, the very idea that you can carry excess weight and still be healthy may sound like an oxymoron. After all, is excess body fat not strongly associated with a wide range of health problems from diabetes to sleep apnea and from arthritis to cancer?
Yes it is, but not in everyone. This is why, in clinical practice, simply measuring body mass index (BMI) or even waist circumference (WC) is never enough to decide who needs to lose weight and who doesn't. Indeed, it is not uncommon to see two individuals with exactly the same BMI -- one with diabetes, hypertension and other weight-related conditions, the other with no detectable health problems at all.
This is why, a couple of years ago, we developed the Edmonton Obesity Staging System (EOSS), which rates actual health status on a five-point scale -- from no weight-related physical, mental or functional problems (stage 0) to severe (end-stage) organ damage and disability (stage 4).
In short, while BMI tells me how "big" my patient is, EOSS tells me how "sick" my patient is.
But can you really be obese and healthy? Will not simply being obese ultimately increase your risk and lead to premature death?
This is exactly the question that we addressed in two recent publications that compared the predictive power of BMI to that of EOSS in three separate, large, longitudinal studies.
In the first study, published in the Canadian Medical Association Journal, we looked at the impact of EOSS on mortality in two separate sets of the U.S. NHANES study -- a representative sample of the U.S. population. In the second paper, published in Applied Physiology, Nutrition & Metabolism, we we looked at the impact of EOSS on mortality in the Aerobics Center Longitudinal Study.
In both studies, BMI alone had little to no power to predict mortality, even over a period of almost 20 years. In contrast, EOSS proved a very powerful predictor of mortality -- incrementally elevated in individuals with EOSS 2/3 (there were no EOSS 4 participants in these data sets), whilst not associated with any mortality risk in EOSS 0 and only mildly elevated risk in EOSS 1 participants.
The surprising finding here, of course, is not that individuals with higher EOSS levels have increased risk -- the surprising finding is that there are indeed a significant number of obese individuals with EOSS 0 (even amongst participants with a BMI greater than 40), who appear to have no risk of premature death from their obesity.
Notably, lower EOSS levels were found in participants who ate more fruit and vegetables and were physically fitter than their higher EOSS level counterparts.
In addition, individuals at higher EOSS levels reported a greater history of previous weight loss -- a finding consistent with the ongoing debate about whether losing weight and putting it back on again (the rule for the vast majority of dieters) is more detrimental to your health than simply trying to live as healthily as possible at your current weight.
So while our studies show that there are indeed individuals who can be fat and healthy, these findings should not distract from the fact that we do have an obesity epidemic and that the vast majority of people with "excess" weight do indeed have relevant comordibities that put them in higher EOSS categories -- for these individuals, improving access to evidence-based preventive and treatment resources must be a priority of any health care system.
In addition, we were also very careful in pointing out that even patients presenting with EOSS 0/1 should be investigated for underlying drivers of weight gain and should be counselled on prevention of further weight gain (weight maintenance) and, insofar there is indeed any additional room for improvement, to eat healthily and get as much activity as they can enjoy.
It is also important to note that we only examined the relationship between EOSS and death. It may well be that individuals with EOSS 0 or 1 may be at increased risk of developing health problems or experiencing other issues, which, while not killing them, may very much impact their quality of life.
Nevertheless, as the results of these studies show, you cannot measure health by simply stepping on a scale and it is certainly far from clear that anyone with a BMI over 30, if otherwise healthy, needs to run out and lose weight.
AMS
Edmonton, Alberta
For more on EOSS and these studies visit www.drsharma.ca
Padwal RS, Pajewski NM, Allison DB, & Sharma AM (2011). Using the Edmonton obesity staging system to predict mortality in a population-representative cohort of people with overweight and obesity. CMAJ : Canadian Medical Association journal = journal de l'Association medicale canadienne PMID: 21844111
Kuk JL, Ardern CI, Church TS, Sharma AM, Padwal R, Sui X, & Blair SN (2011). Edmonton Obesity Staging System: association with weight history and mortality risk. Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme PMID: 21838602