Obesity and Overweight - what do these new studies really mean?

Blogging on Peer-Reviewed ResearchMultiple news sources have been covering this recent article in JAMA (1) which provides epidemiological evidence that being overweight (but not obese) may decrease the risk of some illnesses, while not increasing one's overall mortality from cardiovascular disease.

Given that we've talked about overweight and obesity recently on the blog, I think it's worthwhile to go over these findings in context, and discuss what this paper, and related ones in the literature, actually mean in terms of our health.

Sorry, the news is not all good, you don't want to start putting on the pounds, and the analysis so far in the MSM has been pretty shoddy.

As we discussed before on this topic, the issue that is not obvious in studies like this is that of primary versus secondary prevention. In a survey study like this, we're not looking at a cohort that is truly controlled. Overweight is not being tested as a single variable, and the survey is of people who are of course getting treatment when they develop the morbidities that are known to be risks.

Better drugs, better control of co-morbidities of being overweight and obese, like Diabetes type II, hypercholesterolemia, and hypertension, all known risks of overweight and obesity, have drastically lowered the risk of mortality from being obese. There are also the confounding issues of low weight and weight-loss in the elderly often being associated with illness. So, while modern medicine has largely ameliorated the effects of overweight, that doesn't mean that being overweight doesn't put you at risk for a number of problems. The reason why we look at this study and don't immediately say it's OK to be overweight (even the author of the study makes a point of this in the WaPo article), is because we know that being overweight brings risks - treatable risks, but risks all the same. It's interesting, buried inside the article you also see a major killer of normal weight individuals is injury - and this is much reduced for overweight and obese. Other studies have shown higher suicide and homicide rates in the normal weight population, so it's definitely safer on the couch.

In fact, it's unfortunate that more attention was not paid to the second article, which only gets brief mention in some of the articles. That is the effect of obesity on quality of life and disability(2), which consistent with previous studies (3), shows that while much of the mortality risk from hypertension and comorbidity can be controlled, other morbidities reduce quality of life significantly. They also show the longer you are overweight, the more morbidity you can look forward too.

The abstract from the JAMA article:

Results Among obese individuals, the prevalence of functional impairment increased 5.4% (from 36.8%-42.2%; P = .03) between the 2 surveys, and ADL [activities of daily living] impairment did not change. At time 1 (1988-1994), the odds of functional impairment for obese individuals were 1.78 times greater than for normal-weight individuals (95% confidence interval [CI], 1.47-2.16). At time 2 (1999-2004), this odds ratio increased to 2.75 (95% CI, 2.39-3.17), because the odds of functional impairment increased by 43% (OR 1.43; 95% CI, 1.18-1.75) among obese individuals during this period, but did not change among nonobese individuals. With respect to ADL impairment, odds for obese individuals were not significantly greater than for individuals with normal weight (OR, 1.31; 95% CI, 0.92-1.88) at time 1, but increased to 2.05 (95% CI, 1.45-2.88) at time 2. This was because the odds of ADL impairment did not change for obese individuals but decreased by 34% among nonobese individuals (OR, 0.66; 95% CI, 0.50-0.88).

Conclusions Recent cardiovascular improvements have not been accompanied by reduced disability within the obese older population. Rather, obese participants surveyed during 1999-2004 were more likely to report functional impairments than obese participants surveyed during 1988-1994, and reductions in ADL impairment observed for nonobese older individuals did not occur in those who were obese. Over time, declines in obesity-related mortality, along with a younger age at onset of obesity, could lead to an increased burden of disability within the obese older population.

And similarly from the Finnish study (which is much better - socialism brings reams of data...):

Results During the follow-up of 15 years, obese men who never smoked aged 20 to 64 years had, on average, 0.63 more years of work disability, 0.36 more years of coronary heart disease, and 1.68 more years of longterm medication use, than normal-weight counterparts. Obese women had, respectively, 0.52, 0.46, and 1.49 more years from these conditions than normal weight women. The excess risks of morbidity and disability due to obesity were highest in the youngest age groups and exceeded those of mortality in all age groups. Obese men and women 65 years and older who never smoked had, respectively, 1.71 and 1.41 excess unhealthy life-years (not statistically significant) due to premature need for long-term medication compared with normal-weight subjects, but no excess unhealthy life-years due to coronary heart disease.

Conclusions Obesity has a lifetime impact on disability and morbidity. A further increase in obesity will lead to an increase in unhealthy life-years and in direct and indirect health care costs.

Looking closely at the Finnish study, overweight were at risk for many of these morbidities as well - especially the need for long-term medication - so it's not just obesity that is a risk in these studies; there is a dose-response relationship. Further, in the US study, the problem appears to be worsening, consistent with people being overweight for a larger part of their lives.

So, again, we're talking about primary versus secondary prevention. Yes, it's probably safe to be overweight, with good medical care. But, while it's safer on the couch popping bon-bons and ACE inhibitors, that doesn't make for an excellent life plan. You end up needing more meds, you are more easily disabled, and while the worst of the mortality can be controlled up to a BMI of about 35, that doesn't mean you're not going to have a host of other problems.

My advice based on these studies? Stay thin as long as you can, and exercise. No matter what your weight see your doctor regularly to get your morbidities under control and make sure you're not hypertensive or dyslipidemic (thin people can be too - some people think overweight get better monitoring since doctors are more attuned to risk) . As always, focus for medical professionals should be on treating patients no matter what their weight, because if anything these studies show the high efficacy of preventing cardiovascular mortality with tight medical control of risk factors. Emphasis should never be on weight loss before control of risk factors. But ultimately, being overweight is hard on the body, and the risks of obesity aren't just dying early, but also losing mobility and strength, and having to take more drugs for more problems longer.

1. Katherine M. Flegal; Barry I. Graubard; David F. Williamson; Mitchell H. Gail
Cause-Specific Excess Deaths Associated With Underweight, Overweight, and Obesity
JAMA 2007 298: 2028-2037
2. Dawn E. Alley; Virginia W. Chang The Changing Relationship of Obesity and Disability, 1988-2004 JAMA 2007 298: 2020-2027
3.Tommy L. S. Visscher; Aila Rissanen; Jacob C. Seidell; Markku Heliovaara; Paul Knekt; Antti Reunanen; Arpo Aromaa Obesity and Unhealthy Life-Years in Adult Finns: An Empirical Approach Arch Intern Med 2004 164: 1413-1420

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What gets me is how very little emphasis is always placed in the exercise/active life style part. I think that's the easiest one to control and enhance.

On a different note, a coleage is working on a paper describing a dramatic increase in diabetes drug prescriptions to children between 9 and 19 during the last decade. The largest proportion were girls at the start of puberty.

By TrekJunkie (not verified) on 09 Nov 2007 #permalink

Err... Finland? Socialism? It seems that I've been severely misled for the last couple of decades. Yes, that must be it.

I've always thought that we live in a market economy back here.

I agree with your final analysis, stay thin and fit as long as you can. Whether you are over or average weight, there is no replacement for a healthy lifestyle.

All the data comes from social welfare programs managed by the state. So while you're not "socialists", you do have socialized government-run programs that gather these data.

It seems like weight really shouldn't be discussed much in health. It's about body fat, exercise levels, and diet. The BMI is basically worthless, like anything that tries to measure a cubed change with a square.

In my case, I have a BMI of 31.9, which is obese, but a body fat percentage of 10%, which is below average. And even if I could lower my body fat to 4%, I'd still be more than 30 pounds overweight. But, I should still be wary of the dangers of being overweight? I'll always be overweight.

I like that this study is starting to bring reality to light, which is obesity, by body fat, is bad, but weight really doesn't matter.

I come from a family of people who tend to be overweight, and I tend to think that BMI isn't the whole story either. Through high school, I was quite thin (BMI = 21). I went to university, put on 25 pounds, and am now considered marginally overweight (BMI = 25.5).

But to be honest, I feel healthier at this weight. Before, I tended to have very low blood pressure, would get tired easily, and would black out if I exercised too intensely. Now, I can hike all day (I'm a field biologist), work out as hard as I need to get my heart rate up, and I have a lot more energy.

I'm overweight tho...

The article in JAMA was an excellent study, although labeled as "rubbish" by the Harvard School of Public Health professor Walt Willett.

In the study of data from national surveys, people who were overweight but not obese had a increased rate of death from diabetes & kidney disease, but similar rate of death from cardiovascular disease, and decreased rate of death from other causes compared to people who had a normal BMI. Overall, people who were overweight had a lower age-adjusted death rate.

The data are what they are and it would be a great mistake to then decide to recommend that people with a normal BMI to gain weight. The data also do not measure health or quality of life, etc. In addition, the role of therapy of overweight induced conditions could not be assessed (such as treatment of hypertension, hypercholesterolemia, etc).

Being overweight may have a different implication for young people, compared to middle aged or the elderly. A good rule to follow is the racetrack advice: "The lean horse for the long race."

By Jay Hoofnagle (not verified) on 10 Nov 2007 #permalink

BMI is iften criticized because it is a poor measure of body fat. But why do we use BMI in epidemiology, rather than body fat mass or %? The surprising answer is that BMI is a better risk marker than fatness. That's why it's used. It's also easy to calculate, but these days fatness is also easy to measure evem at home.

Why is BMI better than fatness? The answer is in part that lean body tissue such as muscle is hazardous in excess. Muscle is richly supplied with blood vessles, which is why meat is red. Adipose is pure white --it has very little blood supply. This is why liposuction can be done without bleeding patient to death. Muscleosuction would indeed be fatal.

The loathing and judgemental attitude inspired by adipose tissue is based on an aesthetic judgement more than scientific fact.

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By Joseph M. Vera (not verified) on 11 Feb 2009 #permalink

Globally, there are more than 1 billion overweight adults, at least 300 million of them obese.
Obesity and overweight pose a major risk for chronic diseases, including type 2 diabetes, cardiovascular disease, hypertension and stroke, and certain forms of cancer.
The key causes are increased consumption of energy-dense foods high in saturated fats and sugars, and reduced physical activity. READ MORE :