Scales on bumpy rug

Extra pounds may not cut lifespan

UC DAVIS (US) — Extra weight is not necessarily linked with a higher risk of death, according to a new analysis of national data from nearly 51,000 adults.

When compared to those with normal weight, people who were overweight or obese had no increased risk of death during a follow-up period of six years. People who were severely obese did have a higher risk, but only if they also had diabetes or hypertension.

The findings, which appear in the July-August issue of The Journal of the American Board of Family Medicine, call into question previous studies—using data collected when obesity was less common—linking higher short-term mortality with any amount of extra weight.

“There is currently a widespread belief that any degree of overweight or obesity increases the risk of death, however our findings suggest this may not be the case,” says Anthony Jerant, professor of family and community medicine at University of California, Davis and lead author of the study.

“In the six-year timeframe of our evaluation, we found that only severe obesity was associated with an increased risk of death, due to co-occurring diabetes and hypertension.”

Based on the study, Jerant recommends that doctors’ conversations with patients who are overweight or obese, but not severely obese, focus on the known negative effects of these conditions on mental and physical functioning, rather than on an increased short-term risk of death.

By contrast, Jerant adds that it is important for doctors to talk with severely obese patients who also have diabetes or hypertension about their increased short-term mortality risk and treatment, including weight loss.

“Our results do not mean that being overweight or obese is not a threat to individual or public health,” says Jerant. “These conditions can have a significant impact on quality of life, and for this reason alone weight loss may be advisable.”

In conducting the study, Jerant used nationwide data from 2000 to 2005 of nearly 51,000 adults aged 18 to 90 years who participated in the Medical Expenditure Panel Surveys on health-care utilization and costs. The surveys include information on health conditions such as diabetes and hypertension.

Body mass index (BMI), or weight adjusted for height, was calculated for each respondent. The study categorized people as underweight (BMI < 20), normal weight (BMI 20 to < 25), overweight (BMI 25 to < 30), obese (BMI 30 to 35) or severely obese (BMI > 35). Mortality was assessed using the National Death Index. Of the 50,994 people included in the analysis, just over 3 percent (1,683) died during the six years of follow-up.

The investigators found that severely obese people were 1.26 times more likely to die during follow-up than people in the normal weight group. However, if people with diabetes or hypertension were eliminated from the data, those who were overweight, obese, or even severely obese had similar or even lower death rates than people of normal weight.

Consistent with a number of prior studies, underweight people were nearly twice as likely to die than people with normal weight, regardless of whether diabetes or hypertension was present.

The prevalence of overweight and obesity has increased dramatically in recent decades. An estimated one-third of all US adults over age 20 are obese and another one-third are overweight. In addition to diabetes and hypertension, health problems associated with these conditions include heart disease, osteoarthritis, and sleep apnea.

The relationship between weight and mortality is a controversial topic in public health. Although studies based on data collected 30 years ago showed that mortality risk rose as weight increased, analyses of more recently collected data, including the current one, call this assumption into question.

“Our findings indicate that the risk of having an above-normal BMI may be lower than in the past,” says Jerant. “While this study cannot explain the reasons, it is possible that as overweight and obesity have become more common, physicians have become more aware of associated health issues like high blood pressure, cholesterol, and blood sugar, and are more aggressive about early detection and treatment of these conditions.”

Jerant says that the six-year period of his investigation limits the ability to make assumptions about the link between unhealthy weight and the risk of death over a longer timeframe.

“We hope our findings will trigger studies that re-examine the relationship of being overweight or obese with long-term mortality,” says Jerant.

The study co-author is Peter Franks, professor in the Department of Family and Community Medicine. Franks and Jerant used public access data in conducting the study, which involved no external funding.

More news from UC Davis: http://www.news.ucdavis.edu/

chat11 Comments

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11 Comments

  1. NewEnglandBob

    Wow, that is one UGLY rug!

  2. Frank

    And how strong is the correlation of obesity to diabetes and hypertension? Not to knock on their research but if obesity is a stepping stone another condition which leads to a higher mortality rate then wouldn’t obesity end up being linked to a higher mortality rate? The data to support/refute any correlation would be interesting to see.

  3. LREKing

    Some (especially but not exclusively Taubes) argue that obesity is essentially another symptom (along with diabetes and hypertension) of metabolic syndrome, and NOT the cause. This study would appear to support that, showing correlation but not causation.

  4. LREKing

    BTW, pink rugs are cool. And who has a scale that only goes up to 120 lb?

  5. Rich.G

    A six year follow up isn’t long enough to give a true reflection of whether being overweight affects lifespan. You would need to follow up after 10, 20, 30 years to get accurate data on this.

    People who are overweight are at greater risk of high blood pressure, high cholesterol and type 2 diabetes and each one of these affects lifespan, so it stands to reason that if you are overweight for most of your life, this will likely have and affect on how long you live.

  6. Brian

    I’m seeing some possible autocorrelation problems. This study treats hypertension, diabetes, and obesity as independent variables, when in fact they could be dependent and very highly correlated. By removing those with no hypertension, you could be cherry picking obese people with exceptional vascular systems and then drawing your conclusion from that sample. I have personally found the best way for me to lower blood pressure is to lose weight.

  7. LREKing

    But, speaking or correlation, how do you know that it’s the weight loss that is lowering your blood pressure? How do you know it’s not, for example, a change in diet (specifically eliminating sugars and starches) or other behavioral changes you have made to create the weight loss?

  8. LREKing

    Rich G.–

    “People who are overweight are at greater risk of high blood pressure, high cholesterol and type 2 diabetes…”

    Try this instead:

    “People who are insulin-resistant are at greater risk of being overweight, and having high blood pressure, high cholesterol and type 2 diabetes…”

    In that case, the being overweight itself would not be the cause.

    I understand that NOT blaming the fat person for being slothful and gluttonous goes against decades of (well-intentioned but bad) government and expert advice, but we have to go with the science.

  9. mister m

    Considering that insulin resistance can very often come from eating too much junk food over a lifetime, behavior is still a huge factor in this. And since exercise decreases the risk of death whether or not weight loss takes place, and since diet control helps with insulin problems, I don’t think the popular correlation between obesity and bad health has been broken. After all, human beings were not remotely the size they are now until the past handful of decades–something is badly broken in the way people maintain their health.

  10. John L.

    BMI does not definitively tell us if a person is fat. Overweight yes but not fat. I am a fit 40 year old male with a BMI of 27. My body fat is 17%. If you eliminate all over weight people with diabetes and hypertension you will be left with a high percentage of health individuals with more muscle mass.

    I would be interested in a study that looked at body fat instead of BMI. Until then there is not much I can take away from your study.

  11. knows nose

    I’m a bit confused.
    For example, the article says”…if people with diabetes or hypertension were eliminated from the data, those who were overweight, obese, or even severely obese had similar or even lower death rates than people of normal weight.” By eliminating people from the data who had hypertension or diabetes, the researchers might have been creating a grouping of overweight people with unusually strong constitutions. Then they compared these people with people in the general population, including thin people who, if they were fat, might have developed hypertension or diabetes.

    Also, could the underweight people, who were nearly twice as likely to die as people with normal weight, be thin because they already have some disease killing them? The impression is that being really thin is worse than being really fat.

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