Monday, June 22, 2015

Four Obesity Paradoxes Exposed: Obesity Protects From Chronic Disease > Overweight is CVD Protective > Obesity is Not a Problem if You're Fit > Healthy Obesity is Real

Since scientists still judge obesity by BMI values, athletes contribute to the CVD / mortality  "obesity paradox"
Alright, next to "I don't care, I feel good" you will probably have hear or even read statements like "Don't worry if you're obese. The extra fat is protective" or at least claims like "If you're fit, it doesn't matter if you're fat".

In today's SuppVersity Special I want to take a closer look at these and other claims that are based on observational data that suggest that either all or at least one of the following "obesity paradoxes" exist: (1) Classic obesity paradox - obesity is protective in some chronic diseases; (2) pre-obesity - overweight is protective in normal populations; (3) fat-but-fit - obesity is not a risk factor for mortality in fit individuals; (4) healthy obesity - a sizeable population of obese adults has normal cardio-metabolic risk profiles (McAuley. 2011).
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  1. The classic obesity paradox: Ok, let's start with the biggest bogus, i.e. obesity paradox #1 - obesity is protective in some chronic diseases: Yes, you cannot deny that there appears to be a reduced mortality risk in obese vs. lean patients with known or suspected coronary heart disease (CVD). Now, the real problem, though, is that obesity is also an independent risk factor for CHD (Hubert. 1983; Wilson. 2002).
    Figure 1: Incidence (‰) of myocardial infarction (top, left), congestive heart failure (top, right) and relative odds of dev. cardiovascular disease in the 1st place acc. to age and weight (% of normal | Hubert. 1983)
    As the data in Figure 1 (bottom) shows the risk of developing cardiovascular disease increases by 13%, 29%, 46% for each 10% extra-weight in men and by 8%, 17% and 26% for each 10% extra-weight men. If you also take into account the incidence of myocardial infarctions (top left) and congestive heart failure (top, right), you will have to admit that it would be stupid to rely on not dying from CVD, because you're fat if you can can avoid developing CVD if you don't get fat in the first place?

    In addition, the evidence that normal-weight and even more so underweight CVD patients are at higher risk of not surviving their illness could just as well be a result of reverse causation with the subjects in the normal and low weight range having lost weight due to being sicker than their overweight peers.You don't believe that? Well why do those with the highest weight not have the lowest, but the highest (+88% | Romero-Corral. 2006) CVD mortalities? Convinced? Don't be too sure, there's still one last argument in favor of the existence of an obesity paradox. Who's worse off than someone who is fat and suffers from metabolic syndrome? Well, someone who is not even able to store away the extra energy and suffers from high blood glucose and lipid levels, although he is not obese. If we had sub-group analysis on the normal- and under-weight CVD subjects, I am pretty sure that many will fall into the metabolically deranged skinny fat category. How paradox is it that they don't live longer than their overweight, but in many cases metabolically less deranged peers?
Summary of Mortality from Cancer According to Body-Mass Index for U.S. Men in the Cancer Prevention Study II, 1982 through 1998 (Calle. 2003).
Just because you don't die from CVD, this doesn't mean that you don't die from other things like cancer. Studies show that increased body weight is associated with increased death rates for all cancers combined and for cancers at multiple specific sites. Even in the "only overweight" category (BMI 25.0-29.9), the mortality risk for all cancers is 11% increased in men and 14% in women; and the risk of dying from esophagal cancer increases by 76% in men and 49% in women with that little overweight. So, who cares if there's a questionable risk reduction of 10-something% for CVD deaths?
  1. The pre-obesity paradox: While you certainly cannot rely to survive all your friends if you're simply the fattest, the pre-obesity paradox which says that people in the overweight, but non-obese pre-obesity zone (BMI 25-29.9 kg/m²) will live the longest is much harder to debunk.

    While it is unquestionable that many people who fall into this category suffer from pre-diabetes and pre-hypertension, which in turn are associated with significant increased risk of CVD mortality and all-cause mortality (Tsai. 2008; Ning. 2010). As Karandish and Shirani point out in a recent review "[t]herefore, a gradual increase in mortality risk from pre-obesity to obesity [must be] expected" (Karandish. 2015).
    Figure 2: Risk increase for unhealth non-obese and healthy obese individiuals to transit to unhealthy obesity. After each 5 years, those who already made the transition were removed, so the data indicates that w/ a >12x increased risk most of the "healthy obese" became unhealthy obese in only 5 years (Bell. 2015).
    Now, the bad news for those who feel secure in their "pre-obesity" stage is that studies suggest that more than 40% of those "lucky chubbies" will progress to full-blown obesity (Gopal. 2015 | probably also because overweight is linked to inevitable increases in HbA1C and thus diabetes | Nakajima. 2014).

    To summarize, I would like to cite the conclusion of a letter to the editor of Obesity Research & Clinical Practice in which the author says that "most of healthy obesity may be a transient state" (Nakajima. 2015) - and that's not a hypothesis. It's based on evidence from studies by Soriguer et al. (2013), Appleton, et al. (2013), Bell et al. (2014 & 2015).
  2. The fat-but-fit paradox: You probably won't doubt that fat-but-fit individuals have considerably lower mortality risk compared to normal-weight but unfit individuals. But let's be honest: How many fat-but-fit individuals do you know? None? One? Well, I guess that's because studies show that obesity is a major obstacle to doing what it takes to get and stay fit: exercise (Dalle Grave. 2010; Sallinen. 2009).
    Figure 3: Relative risks of (A) all-cause and (B) cardiovascular disease (CVD) mortality by cardiorespiratory fitness quintiles for 40,451 (2657 all-cause and 943 CVD deaths) men and 12,831 (375 all-cause and 90 CVD deaths) women aged 20–100 years without CVD or cancer (Lee. 2010)
    The practical relevance of the fat-but-fit paradox may thus be marginal, but it's of huge theoretical importance, because any investigation that tries to link objective measures of physical activity or BMI to mortality is fundamentally flawed if the scientists don't adjust their data for the fitness of their subjects (Lee. 2010) - what if all the healthy subjects whose survival brought up the original "obesity paradox" were exceptionally fit? What if they were in fact athletes whose increased lean mass tricked the negligent scientists to believe they were obese, because their BMI is elevated? What if the allegedly "lean" CVD-ridden peers were exceptionally unfit, skinny fat, sedentary and diabetic? Well? Right, in any of these cases the paradox would be the mere result of a lack of attention to important details in the statistical analyses of scientists that like to grab the increasingly obese public's attention by assuring them that they are fine.
  3. The healthy obesity exists paradox: In the discussion of paradox #1-3, we have already confirmed that you can be obese and significantly healthier than some sick normal-weight individuals. This can, but does not have to mean that you also fullfill the official definition which includes the absence of six common cardio-metabolic risk factors (impaired fasting glucose/diabetes, insulin resistance, high triglycerides, low HDL cholesterol, high blood pressure, and high C-reactive protein) in an individual with a BMI ≥30 kg/m².

    The previously discussed evidence that shows that most people rapidly progress from healthy to unhealthy obesity do yet put a huge "?" behind #2 and #3 of the "Health at Every Size" recommendations according to which obese individuals should "trust internal body systems designed to keep us healthy" and "listen to hunger and satiety body signals" - if those mechanisms were fully functional in a world of 24/7 junkfood exposure, no one would be obese - healthy or unhealthy. Compared to yoyo-dieting, though, this strategy has been shown to reduce weight and improve relevant health variables (Bacon. 2002).
5% Calorie Restriction & Longterm Dieting Make You Fat & Insulin Resistant | more
So what? Yes, healthy obesity exists; yes underweight and normal-weight CVD patients can be worse off than overweight CVD patients; yes, you can be fit-but-fat, but all that does not negate the significantly increased risk of all sorts of modern disease (diabetes, CVD, cancer, NAFLD, etc.) that come with the progression from "healthy" to "unhealthy obesity" of which studies show that it is almost inevitable (Nakajima. 2015).

Against that background I consider the talk about "healthy obesity" in the media downright dangerous, because it weakens what should be the most important incentive to keep your weight in check: your health | What do you think?
  • Appleton, Sarah L., et al. "Diabetes and cardiovascular disease outcomes in the metabolically healthy obese phenotype a cohort study." Diabetes Care 36.8 (2013): 2388-2394.
  • Bacon, Linda, et al. "Evaluating a" non-diet'wellness intervention for improvement of metabolic fitness, psychological well-being and eating and activity behaviors." International Journal of Obesity (2002).
  • Bell, J. A., M. Kivimaki, and M. Hamer. "Metabolically healthy obesity and risk of incident type 2 diabetes: a meta‐analysis of prospective cohort studies." obesity reviews 15.6 (2014): 504-515.
  • Bell, Joshua A., et al. "The natural course of healthy obesity over 20 years." Journal of the American College of Cardiology 65.1 (2015): 101-102.
  • Calle, Eugenia E., et al. "Overweight, obesity, and mortality from cancer in a prospectively studied cohort of US adults." New England Journal of Medicine 348.17 (2003): 1625-1638.
  • Dalle Grave, Riccardo, et al. "Cognitive-behavioral strategies to increase the adherence to exercise in the management of obesity." Journal of obesity 2011 (2010).
  • Gopal, J. "Metabolically Healthy Obesity-Is it Really a Distinct Subtype?." Journal of Obesity and Metabolic Research 2.2 (2015): 105.
  • Hubert, Helen B., et al. "Obesity as an independent risk factor for cardiovascular disease: a 26-year follow-up of participants in the Framingham Heart Study." Circulation 67.5 (1983): 968-977.
  • Karandish, Majid, and Fatemeh Shirani. "Controversies in Obesity Treatment." Nutrition And Food Sciences Research 2.3 (2015): 5-14.
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  • Nakajima, Kei, and Kaname Suwa. "Excess body weight affects HbA1c progression irrespective of baseline HbA1c levels in Japanese individuals: a longitudinal retrospective study." Endocrine research 0 (2014): 1-7.
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