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Hi Amy,

Thanks for the comments as always.You are really passionate about EBM.

Considering how obesity is risk factor for almost everything out there, this is such an important paper.

And you said it right. Flegal showed us the data, now it is upto the rest of the people to interpret it and untangle the relationships. If they did the stats wrong, then we better stop reading papers. The people who worked behind are the best in the country. Hence my question about Willet's comments. For me it is strange, we talk about meta analysis being the pinnacle of evidence and how should put money into research, always look at meta analysis, and so forth, yet experts seems to be totally confused about how well was this meta-analysis done. Or maybe it is too obvious to comment and I don't see it. The first comment by Kev is a good example. And not even one single reply!! And this forum is supposed have the best in EBM. I think your  post about "knowledge for all" goes along with this. 

And if someone comes and ask about his meta-analysis and the results, I would hate to say nobody has a clue and start with "I personally prefer". 

Thanks!
Anoop


On Sun, May 5, 2013 at 11:17 AM, Amy Price <[log in to unmask]> wrote:
Hi All,
I wonder if this was simply a pragmatic paper to find out if ideal weight was ideal for the purpose of mortality why the need for explanatory criticisms arise. Could not future research break down explanatory factors? Suppose they observe that fat people are living as long as them and decide to answer the simple question is ideal weight ideal or do those boundaries need reexamination? From there they can look at things like maybe ideal weight in a prosperous society can encompass a greater range or not? Historically what about other civilizations that celebrated plumpness, was there a higher mortality rate? What if metabolic disease kicks in at a higher threshold than previously imagined? Does dieting add to life span and if so by how much…is it worth it? 

(Short subjective rant)
I personally prefer to be slim because I feel healthier but if  the choice means using dieting chemicals and eating food that tastes like used sneakers I am not on board. If I buy something considered decadent or relish my food at a restaurant I want to enjoy this without feeling peer pressure or social guilt. If we make a bid deal about people being fat but can offer them no long lasting resolution like maintained health and weight loss what is the point?

Amy


From: Anoop B <[log in to unmask]>
Reply-To: Anoop B <[log in to unmask]>
Date: Thursday, May 2, 2013 1:42 PM
To: <[log in to unmask]>
Subject: Re: All-Cause Mortality With Overweight and Obesity

Has anyone read the paper yet? I am curious to know what's the clinical significance of a 6% decrease in mortality in the over weight group or what's .94 HR means clinically?

Thank you
Anoop


On Sun, Mar 24, 2013 at 6:11 AM, k.hopayian <[log in to unmask]> wrote:
Hi Anoop,
An interesting question in several ways:
1 A reflection on how we react when evidence conflicts with deeply ingrained beliefs: What, over weight people live longer than 'ideal weight' people? There must be something wrong with this study. 
2 How we non-epidemiologists (evidence-based clinicians as end-users of epidemiology) approach disagreement between experts in epidemiology. Can we take a stand? We can and must even if it is only to acknowledge uncertainty.
3 An appraisal of the evidence itself.

Picking up number 3, I had a look at the paper and did not find anything to justify Willett's assertions that there was no consideration of confounding factors. For example, under data extraction, the authors stated;

"In studies that only presented results stratified by smoking or health condition, we selected results for nonsmokers or never smokers or for those without the health condition."

…and in considering the quality of the analyses in the studies they stated:

"We considered the results adequately adjusted if they were adjusted for age, sex, and smoking and not adjusted for factors in the causal pathway between obesity and mortality, or if they had reported or demonstrated that adjustments or exclusions to avoid bias had shown little effect on their findings."

Now there may be some finer points that elude me so I look forward to hearing from those with more epidemiological knowledge. However, I remain unconvinced that there was no confounding because I am led to ask, What did they do about studies that did not report stratified data or give adequate descriptions of adjustment? And I don't like the fact that they included publications with some overlap in populations. So returning to points 1 & 2 above, my conclusion is that there is probably something wrong with this study but I cannot dismiss it as a pile of anything.

BTW, I can email a copy of this paper for those who want it so long as it is for personal study only.

Dr Kev (Kevork) Hopayian, MD FRCGP
General Practitioner, Leiston, Suffolk
Hon Sen Lecturer, Norwich Medical School, University of East Anglia
Primary Care Tutor, Suffolk
RCGP Clinical Skills Assessment examiner

On 24 Mar 2013, at 04:27, Anoop Balachandran <[log in to unmask]> wrote:

I am curious to know anybody has any comments about Flegal's controversial paper on mortality and BMI:

Here is the link: http://jama.jamanetwork.com/article.aspx?articleid=1555137

Harvard epidemiologist Walter Willett says that the paper is a "pile of rubbish":http://www.hsph.harvard.edu/nutritionsource/questions/ask-the-expert-does-being-overweight-really-decrease-mortality-no/