Monday, July 1, 2013

Sugar Sweetened Beverages, Bottled Water & the Obesity Epidemic: Evidence, Counter-Evidence & Scapegoatism

SSBs worse than an obesity pill?
It is a given fact that neither I nor any sane researcher is going to debate the over-consumption of sugar sweetened beverages are part of the reasons why we are fat. The way they are currently portrayed as the worst invention since trans fats, could however fire back on us. You do just have to look how willingly the oil refiners are bashing the corn refiners, how the fruit "juice" industry claims that their "healthy 100% fruit juices were less obesogenic" than a coke (which is clearly not the case) and how consumers are standing in the line at their local fast-food outlet thinking about taking the diet coke with their menu to be able to have an additional "healthy fruit smoothie" as a dessert.

I had all that in the back of my head already, when I hit on a related "Pro v Con Debate" in the early views (articles that are not yet available in the print edition) of the Obesity Reviews and thought that you might be interest in some of the arguments F.B. Hu and K.A. Kaiser et al. are presenting in their "debate" (in fact we are talking about to separate position papers) on the "Role of sugar sweetened beverages in Obesity", as well.

Point: Sugar sweetened beverages, obesity & diabetes - Scientist says the evidence is there

(Hu. 2013) I would assume that the vast majority of you is not going to have to be convinced by rational or irrational arguments that sugar sweetened beverages will increase your risk of obesity and diabetes. Still, F.B. Hu, a scientists from the Departments of Nutrition and Epidemiology at the Harvard School of Public Health in Boston must have thought of the rest of the public and the bribed, ah... pardon "mislead" policy makers, when they compiled their latest paper with the tell-tale title "Resolved: there is sufficient scientific evidence that decreasing sugar-sweetened beverage consumption will reduce the prevalence of obesity and obesity-related diseases". According to Hu,
Figure 1: Relative risk of the development of obesity per increment of 10 risk alleles, according to intake of sugar-sweetened beverages; data based on the Nurses’ Health Study (NHS) and Health Professionals + follow up (HPFS), the Women’s Genome Health Study (WGHS) and the three cohorts together (Hu. 2013)
"Consumption of SSBs has increased markedly across the globe in recent decades, tracking closely with the growing burdens of obesity. These beverages are currently the largest source of added sugar intake and the top source of daily energy in the U.S. diet. The cumulative evidence from observational studies and experimental trials is sufficient to conclude that regular consumption of SSBs causes excess weight gain and these beverages are unique dietary con- tributors to obesity and T2D. Compelling evidence indicates that reducing SSBs will have significant impact on the prevalence of obesity and its related diseases, especially T2D. [...] Although reducing SSB consumption alone is unlikely to solve the obesity epidemic entirely, limiting intake of SSBs is one simple change that could have a measurable impact on weight control and prevention of T2D and other metabolic diseases" (Hu. 2013; my emphasis)
Hu also points to the "strong resistance from the beverage industry" and the few, but increasingly numerous  public policies and regulatory strategies to reduce intake of SSBs that are already in place or being developed. The importance of a grass-roots approach, on the other hand appears to escape him. After all, it often does not look like this, but in the end the US is still a free country: You don't have to drink Pepsi, Coke and Mountain Dew, folks and neither do your friends and family.

Counterpoint: Sugar sweetened beverages are bad - in theory, but what about the reality?

(Kaiser. 2013) Now that your conviction that sugar sweetened beverages are bad, has been confirmed. let's shake the evidence and take a peak at what K. A. Kaiser, J. M. Shikany. K. D. Keating and D. B. Allison have to say about the question whether reducing sugar-sweetened beverage consumption will reduce obesity and why they feel that "[The e]vidence supporting conjecture is strong, but evidence when testing effect is weak".
Theory vs. experimental evidence: In fact the theoretical slope of the line depicting the increase in weight gain due to the consumption sugar sweetened beverages is more than 10x steeper than the one that has been observed in scientific studies (see figure 3).
What is particularly interesting is that the theoretical prediction is accurate only in the lowest 10-15% of the SSB intakes investigated in the study, for the "real SSB junkies" the gab widens significantly.

Figure 2: Rise in obesity rates (round markers) and bottled water consumption (square markers) in the US (Kaiser. 2013)
If you take a look at the graph to the right (figure 2) you will notice right away: We can as well blame the obesity epidemic to the increase in bottled water consumption (or the decrease in tap water consumption?) - the epidemioloical "evidence" is conclusive!

This figure is yet not the only thing Kaiser at al. enlist to make you at least reconsider how conclusive the evidence of which Hu just argued that it is "there" actually is. The most important factors Kaiser, Shikany, Keating and Allison want to remind us of, when it comes to the interpretation and evaluation of the hitherto available studies are...
  • the risk of bias -- Most scientists start out with the same conviction we do: "Sugar sweetened beverages make you fat!" Against that backround it is even more detrimental that  "some study designs failed to adequately isolate treatment effects from the attention researchers paid to some groups." (Kaiser. 2013) The researchers also point out that not all studies had an objective measure of participant compliance (returned containers, urinary sucralose measures) and did not report whether the people who accessed the effects were blinded as well (10 out of 15 studies did not). Publication bias, on the other hand, did not appear to be a factor to skew the results (Kaiser. 2013)
  • missing / insufficient sensitivity analysis -- In their re-analysis the researchers found sign. differences in the obesogenic effects of SSBs on young vs. old, male vs. female and lean vs. obese participants, yet the majority of the studies does not accordingly differentiate the outcomes.
    Figure 3: Observed (30,34,40–42,62) versus theoretical (63) weight gain effect of mandatory sugar-sweetened beverage (SSB) consumption (Kaiser. 2013)
    "[...] we evaluated the overall summary effects by excluding the studies referenced above. The overall SMD for the added SSB studies (adults only) increased by 0.06 (to 0.34; 95% CI: 0.15 to 0.54). The overall SMD for the reduction of SSBs in children of all weight categories was reduced by 0.01 (to 0.07; 95% CI:  -0.01 to 0.15). The overall SMD for the reduction studies in children only who were overweight or obese at baseline increased by 0.05 (to 0.30; 95% CI: 0.13 to 0.46)." (Kaiser. 2013)
    The general heterogenity (all variables included) is yet not another contributor to significant changes in the study outcomes.
  • data interpretation / analysis - The scientists suggest that analyzing only absolute weight / BMI levels is not an adequate measure and propose two different methods to evaluate the data
    1. Asking the question, whether a person that is in the "SSB" group would increase or decrease weight / BMI if he or she switched to the other group - This analysis yielded a +2% and +7% change of weight / BMI reduction.
    2. Using the correlation data as basis to calculate the explanatory value of SSB consumption - This analysis showed that only 1.92% of the variance in body weight or BMI change is explained by SSB consumption, for the variance weight reductions in persons of all weight categories the figure is a hilariously irrelevant 0.09%
    As you can see, looking at the data from a marginally different angle can easily make all the difference. 
I know what you are thinking now "but XY said..." or "but what about..." and obiously Kaiser et al. must also have thought about objections like these and added a brief adjunct to their paper in which they point towards three major reasons that explain why the influence of sugar sweetened beverages is perceived as larger than life by the public:
  1. Don't get me wrong, I love the "ads" of the NYC Dept. of Health & Mental Hygiene campaign against sugar sweetened beverages, and used it as title picture for a previous post on the fattening effects of SSBs, but they are part of the problem Kaiser et al. are pointing at in their paper. People will sit next to them think about the gym and say: "Well I drink diet coke, so I don't have to go to the gym today - after all sugar is the problem!"
    Emotion-raising language - Emotion-raising language has often been used in discussions of SSBs and obesity. Some authors have used words like ‘plague’, ‘toxic’, ‘hazardous’ (4,53) and ‘deadly’ when describing SSBs or the sugars they contain and have tried to promote perceived connections between SSB marketers and the worst behaviour of tobacco marketers . Although such words may help to advance an agenda, they do not educate or inform the public.

    Moreover, they likely raise emotions and impair logical reasoning. As Kersh and Morone wrote, ‘Scientific findings never carry the same political weight as does a villain threatening American youth.

    If critics successfully cast portions of the industry in this way, far-reaching politi- cal interventions are possible, even likely. When an industry becomes demonized, plausible counterarguments (privacy, civil liberties, property rights, and the observation that “everyone does it”) begin to totter.’
  2. Distortion of scientific information - A second factor that has likely contributed to misperceptions in this area is the distortion of scientific information by some authors and commentators. [...] Clearly, such practices mislead and have likely contributed to misperceptions in the scientific and lay communities about the strength of the evidence regarding the proposition debated here.
  3. The mere exposure effect - The final factor that we believe has led to the erroneous perception that the evidence showing that the proposition of this debate has been unequivocally proven is the ‘mere exposure effect.’

    The mere exposure effect is the label psychologists use for the phenomenon that the more a person is exposed to an idea, the more they come to like and accept it. As the Nobel Prize-winning economist Daniel Kahneman described, ‘A reliable way to make people believe in falsehood is frequent repetition, because familiarity is not easily distinguished from truth. Authoritarian institutions and marketers have always known this fact. But it was psychologists who discovered that you do not have to repeat the entire statement of a fact or idea to make it appear true’

    The number of articles on SSBs and obesity and the number of statements that SSBs are especially problematic in obesity are extraordinary, especially in comparison to the modest amount of probative data. Thus, opinions about SSBs may have been offered so often that these opinions have become accepted as fact by many in the scientific community, media and lay public.
I probably could quote addtional parts of the excellently written paper here, but I guess you are getting the notion and will be able to understand that neither my nor the scientists who wrote the original paper intend to support the position of the SSBs industry that have long realized that this war cannot be won on the scientific stage and have long focused all their efforts having their "lifestyle" drinks being marketed by the "cool and hip" celebrities, athletes and super models to the "wanna be cool and hip" normals.

Bottom line: I am well aware that some of you are now probably already dialing the Dr. Lustig's phone number or calling the blogosphere's vice police to accuse me of making a pact with the Coca Cola company.

You all know I am an opponent of the consumption all sugar & HFCS sweetened drinks and foods and well aware of the "fat consequences" (learn more), but overemphasizing the roles of SSBs or HFCS, is not going to help us solve the global obesity problem.
But let's be honest, you all know that I neither drink nor recommend anyone to drink sugar sweetened beverages. My interest is in understanding the contributions each and every of the myriad of dietary, behavioral, endocrine, paracrine, neurological, environmental, social, ... to the obesity epidemic and if you take a look the 1.92% explanatory value of SSBs consumption in terms of body weight and BMI, it is clear that sugar sweetened beverages are a major contributor to the obesity epidemic.

Still it is not warranted and would be a consequential mistake to expect that by taking them off the market the whole issue would be solved. We all know that this won't be the case and you just have to look at the non-existent long-term effects switching to diet sodas had on the waist lines of the obese to know that we have to do more than remove all sugar sweetened beverages from the displays of the supermarket.

Does this mean we should not tell people they are bad for them? Try to tax or ban them? No. What it does mean, though, is that the war against obesity is not a war against SSBs, only.

  • Hu FB. Resolved: there is sufficient scientific evidence that decreasing sugar-sweetened beverage consumption will reduce the prevalence of obesity and obesity-related diseases. Obes Rev. 2013 Jun 13.  
  • Kaiser KA, Shikany JM, Keating KD, Allison DB. Will reducing sugar-sweetened beverage consumption reduce obesity? Evidence supporting conjecture is strong, but evidence when testing effect is weak. Obes Rev. 2013 Jun 7.