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Obese, but Metabolically Healthy Individuals: at Lower Risk of Death?

Friday, August 20, 2010 Posted by Peter Janiszewski, PhD

Very recently, an interesting study was published looking at the risk of early mortality among metabolically-healthy obese individuals – a topic we’ve covered on a number of occasions on Obesity Panacea. The authors of this landmark study published in the journal Diabetes Care are actually close friends of ours (Dr. Jennifer Kuk and Dr. Christopher Ardern), and both are alumni of Queen’s university. Now that the media frenzy surrounding their recent study has subsided, Dr. Kuk was kind enough to answer a few questions about the study and enlighten our readers.

Dr. Kuk is currently an Assistant Professor at the School of Kinesiology and Health Science at York University. Before Dr. Kuk was at York University, she did her PhD in the same lab that I am currently in (Queen’s university). Dr. Kuk has been instrumental in shaping my research interests while at Queen’s and beyond, and over the years has provided tremendous guidance in many areas. I could not be happier to showcase some of her pioneering research on Obesity Panacea.

Without further adieu, enjoy the interview.

OP: If you were to sum up the main findings of your study to a non-scientist at a dinner party, what would you say?

Dr. Kuk: I don't get invited to dinner parties, but if I were, I'd say that "My study shows that individuals who are obese and do not have common diabetes and heart disease risk factors die at the same rate as those who do. This means being overweight alone puts you at higher risk for dying, even though you do not high blood pressure, high cholesterol or high blood sugar. This highlights the negative health impact of body weight alone".

OP: Why do you think the prevalence of metabolically-healthy obesity in your study was so much lower than previously reported in others (6% vs 20-30%)?

Dr. Kuk: The prevalence was lower in our study as compared to others simply because we used a more strict definition of metabolically normal. Other studies used insulin resistance or the metabolic syndrome (3+ risk factors) alone, but we defined 'metabolically healthy' as the absence of insulin resistance or any metabolic syndrome criteria. We felt this would be a more accurate definition of 'metabolically healthy' as each of the metabolic syndrome criteria are associated with morbidity and mortality alone.

OP: How do you reconcile the findings from the current study with those of prior studies suggesting that metabolically-health obese individuals are at no greater risk for developing type-2 diabetes or cardiovascular disease than normal weight individuals?

Dr. Kuk: Although I don't know which studies you are referring to exactly, but in our study, 80% of the deaths in the metabolically-healthy obese were due to cancer and 'other' causes. Other causes are likely traumatic injuries, which highlights an important point. Obese individuals are less likely to survive a trauma as compared to normal weight individuals despite similar injuries. This is related to longer transport times due to their higher body weight, and difficulty assessing and treating the injuries due to their increased size. Further, they are less likely to see their physicians regularly, which may be in part why cancer is generally diagnosed in obese individuals at later stages. Thus, this study fits in line with the idea that these indiviudals are not more likely to develop these metabolic diseases, but still die from other causes.

OP: Recently, Drs. Sharma and Kushner proposed a new staging system for obesity treatment suggesting that obese individuals without established metabolic risk should be counseled to maintain current weight, rather than lose weight (Read about this on Dr. Sharma's Obesity Notes blog). Do the results of your study agree or disagree with these recommendations?

Dr. Kuk: One can examine this question from a theoretical or practical standpoint. From a theoretical stand, weight loss improves metabolic factors, functionality and serveral psychological and social factors, and thus it would be intutitive to recommend that all obese lose weight. However, from a practical perspective it may be unethical to recommend an individual who is not presenting with overt disease to try to lose weight as most indiviudals fail to maintain their weight loss over the long term. Repeatedly failed attempts to maintain weight loss has been shown to elevate one's risk for diabetes, CVD and cancer for a given BMI. In other words, it may be better to recommend maintenance of weight rather than prescribing weight loss, knowing that they are likely to fail and be worse off because of it. Though we did not examine this issue, Sharma and Kushner's staging system examines non-metabolic consequences as well, and it is reasonable to assume that these are equally important to examine as they are also important aspects of health, and inclusions of these factors may alter the associations observed.

OP: Are metabolically-healthy obese individuals actually healthy?

Dr. Kuk: I think that whether metabolically-healthy obese are actually healthy is dependent upon the accuracy of the definition. As we see that obese without CVD or diabetes risk factors are at elevated cancer risk implies that our definition of metabolically healthy is not capturing cancer metabolic risk factors. Similarly, risk for trauma events may also reflect aspects of health that may or may not be captured by metabolic risk factors, but are crucial aspects of health. For example, musculoskeletal fitness would be a predictor of risk of falling or functionality.

Thus, if we used a more encompassing definition, we would likely see that these metabolically-healthy obese may be at lower risk for mortality and are healthy. However, as our definition only identified 6% metabolically healthy obese, I would suspect that an all encompassing definition for healthy obese would be a very minuscule proportion of the population.

OP: What was the most interesting point raised by a reviewer during the publication process of this study?

Dr. Kuk: The most interesting point was surrounding whether metabolically normal obese should lose weight. I don't think there is a clear answer, but this study definitely provides food for thought.

OP: What came as the biggest surprise to you in doing this study?

Dr. Kuk: Our main finding was the biggest surprise. We actually expected that the metabolically normal obese were at lower risk for mortality.

Thanks very much to Dr. Jennifer Kuk!

Have a great weekend!

Peter

Originally posted on November, 2009.

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Kuk, J., & Ardern, C. (2009). Are Metabolically Normal but Obese Individuals at Lower Risk for All-Cause Mortality? Diabetes Care, 32 (12), 2297-2299 DOI: 10.2337/dc09-0574


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3 Response to "Obese, but Metabolically Healthy Individuals: at Lower Risk of Death?"

  1. Anonymous Said,

    Do you know if they took age into account, since cancer occurs more frequently with increasing age?

    Posted on August 20, 2010 at 3:21 PM

     
  2. Miriam Gordon Said,

    Thanks for posting this, it's nice to see that you have an open mind and are willing to present all the evidence. Have you ever heard of "Health at Every Size" (HAES)? This post actually supports a lot of HAES tenets. Dr. Linda Bacon (http://lindabacon.org) wrote the book - I think you'll find it interesting. Maybe you'll even reconsider your blog's subtitle and rethink searching for a "cure" for "obesity."

    Posted on August 22, 2010 at 1:03 AM

     
  3. Carlie Said,

    Further, they are less likely to see their physicians regularly, which may be in part why cancer is generally diagnosed in obese individuals at later stages.

    That component means that it's not being obese that's the problem there, but rather the way they are treated when being a patient. It's disingenuous for him to lump that in with the other reasons without noting the difference.

    Posted on September 1, 2010 at 9:38 PM

     

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We are PhD students in the School of Kinesiology and Health Studies at Queen's University in Kingston, Ontario. Our research focuses on the relationships between obesity, physical activity, and health risk. This blog is our attempt to consider the many "cures" for obesity that we read about on a daily basis. Enjoy.

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