Is Being Overweight Healthy?
You might have heard about the meta-analysis released January 2 in the Journal of the American Medical Association, Association of All-Cause Mortality with Overweight and Obesity (1), which found that “overweight” people, based on body mass index (BMI) had a lower risk of mortality than what is considered a healthy BMI.
Before I had a chance to read the study myself, I came across a USA Today article, Experts weigh in on the dangers of extra pounds, quoting the well-respected nutritionist, Dr. Walter Willett from Harvard School of Public Health, about the JAMA study:
“The most serious problem in the paper is that the normal-weight group included a mix of lean and active people, heavy smokers, patients with cancer (and) other conditions that cause weight loss, and frail elderly people who had lost weight due to rapidly declining health. Because the overweight and obese groups were compared to this mix of healthy and ill persons who have a very high risk of death, this led to the false conclusions that being overweight is beneficial and that grade 1 (moderate) obesity carries no extra risk. The new statistics are completely misleading for anyone interested in knowing about their optimal weight. … The paper is a pile of rubbish.”
Yikes! That’s quite a rip on the JAMA study’s authors. Not only that, but why would a research group put so much effort into a meta-analysis but fail to adjust for some of these obvious confounders, and why would JAMA publish it?! But Willett’s criticisms would explain how they could have reached such a counter-intuitive finding and all would still be good in the nutrition universe.
I read the study fully intending to find the criticisms by Dr. Willett to be valid. Alas, I did not. From my reading of the paper, they did adjust for smoking and age, and analyzed the study for any bias due to “frail elderly people.” They did some testing to make sure previous heart disease and cancer were not affecting the results.
The control groups for the studies in the meta-analyses were typically people with a BMI of from 18.5 to < 25 or from 20 to < 25. The study found that people with a BMI of 25 to < 30 had a statistically significant 8% reduced risk of mortality (.92, .88-.96). People with a BMI of 30 to < 35 had essentially the same risk of mortality. It wasn’t until you got to the group of people with a BMI of 35 or greater that risk of mortality significantly increased.
So, what could be going on here? Well, a BMI of 18.5 to 20 has often been considered to be unhealthfully thin, but from what I gleaned from the paper’s discussion, excluding such people did not appreciably affect the results.
BMI doesn’t account for muscle mass, as Willett alludes to above, but it is hard to believe that there were enough muscle-bound people in the meta-analysis to confound the results to any significant degree.
Willett went on to say in the interview:
“In the last several years, two other major analyses, involving the collaborative efforts of more than 150 scientists, have been conducted on the relation of body weight to mortality…these studies showed clearly that both overweight and all grades of obesity are associated with increased mortality.”
In contrast, the JAMA authors mention that their results are consistent with two previous meta-analyses. And they give some reasons why being overweight might be associated with lower risk of mortality:
“Possible explanations have included earlier presentation of heavier patients, greater likelihood of receiving optimal medical treatment, cardioprotective metabolic effects of increased body fat, and benefits of higher metabolic reserves.”
Occam’s razor would dictate that the best explanation is simply that it’s healthier to be “overweight,” and I don’t like doing backwards somersaults to wish away findings that, had they gone the intuitive way, would be unquestioned as solid. That said, given the prevalence of type 2 diabetes and the fact that vegans have been shown to have a much lower rate of type 2 diabetes and much lower average BMIs, I’m not going to try to gain weight. But it’s a little demoralizing to have one of the most basic ideas in nutrition ̵ that being overweight is not better than being a normal weight ̵ significantly questioned.
In conclusion: Rubbish? Not from what I can tell. Food for thought? Yes. As is often the case, this isn’t the last word.
Reference
Flegal KM, Kit BK, Orpana H, Graubard BI. Association of all-cause mortality
with overweight and obesity using standard body mass index categories: a
systematic review and meta-analysis. JAMA. 2013 Jan 2;309(1):71-82. |
link
January 11th, 2013 at 5:14 pm
Thanks for posting about this! It sounds like this could be a good start for changing the bmi classifications. Maybe its not so much that being overweight is healthier, but that 25-29.9 need to reclassified as normal.
January 11th, 2013 at 9:05 pm
In what sense did the study adjust for the variables mentioned by Willett? The meta-study merely excluded some non-standard categories, that isn’t the same as adjusting for (i.e., conditioning on) a particular variable. This study doesn’t address the issues raised by Willett, indeed, in today’s world were being overweight is the norm its very plausible that being slim is correlated with an underlying medical condition rather than healthy lifestyle.
As for Occam’s razor, given decades of research that conflicts with this study the most likely explanation is that the study is flawed.
Also, this study would have been more interesting if they also look at morbidity.
January 11th, 2013 at 9:33 pm
Tyler,
My understanding is that the individual studies adjusted for those variables.
> As for Occam’s razor, given decades of research that conflicts with this study the most likely explanation is that the study is flawed.
But this “study” isn’t just one study – it’s dozens of studies put together. Many studies agreed with this meta-analysis – they had to or the meta-analysis couldn’t have found what it did. But given that two other meta-analyses apparently found the opposite, your point is at least half-right (or mine is half-wrong), in my opinion.
January 12th, 2013 at 1:44 am
Sorry for going off topic here: I have a plan for 2013 to increase my muscle mass a bit and have starting researching some of the vegan fitness type of sites. There one suggestion is to take “branched chain amino acids” supplement right before and after workouts. Can you say something about research on that? Is there research showing it useful? Are there any health drawbacks? Are there any known vegan brands?
January 14th, 2013 at 2:58 pm
edi,
I plan to do a post on branched chain amino acids in the next few days or so.
January 12th, 2013 at 12:36 pm
I have always thought the best thing to do is maintain a “normal for you weight” and exercise a lot to maintain bone and muscle. People are very different and all this BMI stuff can be obsessive for some. My daughter is thin and weighs 150 at 5′ 8″ Everyone is different. We have to stop using charts and numbers to tell us we’re ok.
January 12th, 2013 at 6:19 pm
HI Jack, me again– The obese vegan, who’s been vegan now for 4 years this February.
Do you think that if all the health numbers are good, and a person is in good health, that being overweight or obese is still harmful? I’m confident that I’m leaps healthier than a typical American diet woman, I still worry about the estrogen effects of obesity. My weight is mostly on my lower half, and outside my muscles, not inside.
January 14th, 2013 at 3:05 pm
Kathleen,
> Do you think that if all the health numbers are good, and a person is in good health, that being overweight or obese is still harmful?
I don’t feel certain, but according to this study, you are not at higher risk for early death. There is a lot of thinking these days that if you are “fit”, measured typically by VO2 Max, but also could include muscle-mass, then you are in good health. I would be mostly worried about glucose tolerance, cholesterol, triglycerides, and c-reactive protein. If all of those are good, and you’re fit, then my money is on you.
January 13th, 2013 at 1:40 pm
As an overweight vegan who loves to exercise and eats healthily, I appreciate your thoughtful words. Too many people are willing to jump on the bandwagon and fat-hate and fat-bash despite whatever science says. This is the first I am reading of your work, as I came here after PeaCounter.com was recommended to me, and I am interested in reading more of what you have to say.
I encourage you to look in depth into the Health At Every Size movement if you haven’t done so already. The important thing, I think, from a moral and ethical standpoint is to encourage everybody to make healthy choices and refrain from judgments about body size. The truth is that many factors go into how a person is, what shape they are, and how healthy they are.
January 14th, 2013 at 2:47 pm
The JAMA study just combined the results from almost 100 separate published studies. Each one of those published studies was written by scientists and accepted for publication in a peer-reviewed journal. All the studies adjusted their results for muliptle variables and lots of them addressed in various ways these issues of smokers, sick people and so on. Willett must think all these 100 studies are indiividually “rubbish” because the JAMA study just summarizes what they all show!
January 15th, 2013 at 8:50 pm
edi,
My branched chain amino acid post:
http://jacknorrisrd.com/?p=3512
January 16th, 2013 at 12:26 pm
When I table or give a vegan cooking class, I got asked so many times about my protein, calcium and iron levels that I went and printed out my EPIC stats to show people from now on! They are all in the normal to high range! 🙂
Here’s what you are asking about:
GLUCOSE 92 70 – 105 mg/dL (It usually runs low)
CHOLESTEROL 184 0 – 200 mg/dL
TRIGLYCERIDE 64 0 – 150 mg/dL
I haven’t had my c-reactive protein tested, at least my EPIC records don’t have CRP results. Shall I get it tested?
I do have elevated LDL, which I’m working on lowering with a daily dose of ground flaxseed. (I had my Omega 3 levels checked, and they were on the mildly low side, so this will help that too!)
LDL- CALCULATED 119 3 – 100 mg/dL
Thank you for your reply! 🙂
January 16th, 2013 at 6:31 pm
Kathleen,
I’m not sure how common it is to test for CRP, but you could ask your doctor about it. Here is some more info:
http://www.mayoclinic.com/health/c-reactive-protein/my01018
January 16th, 2013 at 5:45 pm
Please reread the article. The authors DID NOT adjust for chronic disease or cancers in their overall analysis.
“Studies that addressed these relationships only in adolescents, only in institutional settings, or only among those with specific medical conditions or undergoing specific medical procedures were excluded. ”
“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. A number of studies (for example15- 29) reported qualitatively that such adjustments had little or no effect without showing quantitative details.
Other studies (for example30- 32) demonstrated little effect through a series of sensitivity analyses. We considered the available full sample results from such studies to also be adequately adjusted. Otherwise, we considered studies as possibly overadjusted if they adjusted for factors such as hypertension that are considered to be in the causal pathway between obesity and mortality or as possibly underadjusted if they did not adjust for age, sex, and smoking. We classified 53 studies as adequately adjusted, 34 studies as possibly overadjusted, and 10 studies as possibly underadjusted.”
In fact, when they reanalyzed the overweight cohort to adjust for cancer, heart disease and smoking, the overweight cohort had a higher hazard ratio than the normal weight cohort.
“For the overweight category only, we also repeated analyses including the results from a study that pooled data from 19 cohorts. After excluding ever smokers and those with a history of cancer or heart disease, Berrington de Gonzalez et al8 found a HR of 1.11 (95% CI, 1.07-1.16) for men and 1.13 (95% CI, 1.09-1.16) for women with a BMI of 25 to 29.9 relative to those with a BMI of 20 to less than 25 (Amy Berrington de Gonzalez, DPhil, written communication, June 16, 2011).”
January 16th, 2013 at 6:27 pm
Michelle,
> The authors DID NOT adjust for chronic disease or cancers in their overall analysis.
I didn’t say they adjusted for chronic disease or cancers, I said, “They did some testing to make sure previous heart disease and cancer were not affecting the results,” as shown by continuing to read the section you were quoting above:
> “For the overweight category only, we also repeated analyses including the results from a study that pooled data from 19 cohorts. After excluding ever smokers and those with a history of cancer or heart disease, Berrington de Gonzalez et al8 found a HR of 1.11 (95% CI, 1.07-1.16) for men and 1.13 (95% CI, 1.09-1.16) for women with a BMI of 25 to 29.9 relative to those with a BMI of 20 to less than 25 (Amy Berrington de Gonzalez, DPhil, written communication, June 16, 2011).”
They go on to say:
“Our analysis included published studies using 6 of the same cohorts, representing about 60% of the original Berrington de Gonzalez et al sample. Excluding those studies from our analysis and substituting the above results from Berrington de Gonzalez et al did not change the summary HR for overweight.”
January 16th, 2013 at 6:10 pm
@CarolynS:
Dr. Willett is an MD, PhD and is the Chair of the Department of Nutrition at Harvard School of Public Health. He understands scientific review and evidence based medicine better than the majority of Americans.
Meta-analysis is known for overestimating effect. Just because you have numerous articles which include similar data does not automatically mean can add that data together and come to a correct conclusion. Scientific review is not just adding 2 + 2 together to make 4. Analysis of data is much more complicated.
Also, there are hundreds of scientific studies published every year in peer review journals that end up being proven false.
January 16th, 2013 at 6:50 pm
A bit more on this BMI topic if you’re interested:
http://jacknorrisrd.com/?p=3489
January 17th, 2013 at 6:55 pm
Thanks!
I’m 5 foot 4, and over 240 pounds, so my BMI isn’t too inaccurate, ha! 😉
January 17th, 2013 at 8:49 pm
Kathleen,
As you probably know, that gives you a BMI of 41.2 which is in the range associated with early death, so I misspoke earlier, not realizing your BMI was above 35. I don’t want to be a downer, but I also don’t want to give you false information. I don’t know if being fit will negate the higher risks.
I was also going to add that eating apples and oatmeal can help reduce cholesterol.
January 18th, 2013 at 11:05 am
Kathleen – aerobic exercise is also really important for LDL control!
Jack –
I have definitely seen previous articles (I guess likely included in this analysis) that claimed lower mortality rate for heavier individuals and I remember one in particular that talked about it being particularly important in the elderly because the thought was that carrying more weight was protective against osteoporosis and injuries sustained in falls. Also that if you were heavier you probably were getting better nutrition and malnutrition is a common problem in the elderly and associated with both physical and mental decline. I can definitely believe all of that, as my 96 year old grandmother, who was unwaveringly obese all her life, was in such better shape that all of her peers in her senior housing building who were thinner. She clearly had good reserves!
But also, I don’t think this research or any other research that brings up the “obesity paradox” is actually that surprising or that it negates the general idea that thinner people do better than heavier people. We already knew that people who were too thin were at increased risk, so all we might be saying now is that the range of normal is different. We might say a BMI of 20-35 is “normal, low risk” (as long as you’re not in the lower end because of smoking or weight loss due to illness and that everyone in that range should work on fitness and healthy diet no matter what to decrease risk of heart disease and diabetes), >35 and <20 is high risk. This may not agree with conventional wisdom of the past 75 years, but it actually does agree strongly with conventional wisdom of all time before that, when being zaftig was a sign of health and likely longevity.
While diabetes and heart disease are lifestyle diseases that are more likely when you're heavier (even in the range where mortality risk is decreased), they're also just longevity diseases – if the total population lives longer, we should expect more of them even if everybody is doing everything they can to be healthy. So it seems like it makes a lot of sense to expand the range of normal so that when you show up at your doctor's office, they don't say "lose weight" they say "eat more plants, do more aerobic and strength-training exercise, work on your balance." "Lose weight" is useless advice and it's actually really helpful in the clinical setting to try to take that off the table.
January 18th, 2013 at 12:00 pm
I eat apple every day, at least a half of one in my morning smoothie.
I’m practicing on only eating when I’m hungry, and stopping when I’m full, and drinking water first to see if it’s thirst or hunger. Long process, and rather discouraging at times, as I’m 38 and I’d like to get skinny before I get old.
Aerobic exercise is pretty out of the question right now, as I have reactive airway asthma, fibromyalgia, and back problems. I do try and keep active though, especially in the warmer months with badminton, biking, swimming, and walking.
January 20th, 2013 at 8:12 pm
Michelle, I believe that when John Ioannidis wrote an article listing highly cited observational studies whose findings were later contradicted by randomized trials,the Nurses Health Study led the pack. Many of the findings from the Nurses study have been shown to be wrong – vitamin E for heart diease, beta-carotene for cancer, for example. So yes, it’s true that incorrect findings may be published.
Meta-analysis is a standard method for combining many studies. I believe you will find that Dr Willett himself has been a coauthor on various meta-analyses:
1: Bernstein AM, Ding EL, Willett WC, Rimm EB. A meta-analysis shows that
docosahexaenoic acid from algal oil reduces serum triglycerides and increases
HDL-cholesterol and LDL-cholesterol in persons without coronary heart disease. J .Nutr. 2012 Jan;142(1):99-104.
2: Pan A, Sun Q, Bernstein AM, Schulze MB, Manson JE, Willett WC, Hu FB. Red meat consumption and risk of type 2 diabetes: 3 cohorts of US adults and an updated meta-analysis. Am J Clin Nutr. 2011 Oct;94(4):1088-96.
3: Bischoff-Ferrari HA, Dawson-Hughes B, Baron JA, Kanis JA, Orav EJ, Staehelin HB, Kiel DP, Burckhardt P, Henschkowski J, Spiegelman D, Li R, Wong JB, Feskanich D, Willett WC. Milk intake and risk of hip fracture in men and women: a meta-analysis of prospective cohort studies. J Bone Miner Res. 2011 Apr;26(4):833-9.
4: Soedamah-Muthu SS, Ding EL, Al-Delaimy WK, Hu FB, Engberink MF, Willett WC, Geleijnse JM. Milk and dairy consumption and incidence of cardiovascular diseases and all-cause mortality: dose-response meta-analysis of prospective cohort studies. Am J Clin Nutr. 2011 Jan;93(1):158-71. :