HOW TO PREVENT CANCERS

With a cut off of BMI at 25 defining overweight, we see that risk of diabetes, gall stones, and high blood pressure and heart disease are all elevated, and the risk continues to rise with higher levels of adiposity or BMI. This is true in the first figure – showing the relative risks for women, and in the second for men.

Relative Risk of Diabetes, and other chronic conditions by level of Body mass Index (BMI)

Women




Men




We recently completed and analysis of national data to predict life years lost associated with obesity-related diseases for U.S. non-smoking adults, and to examine the relationship between those obesity related diseases and mortality.10 We used data from the National Health Interview Survey, 1997-2000 (see report).

We analyzed these data to estimate the association between those obesity related diseases and mortality and used simulations to project life years lost associated with the diseases.

What did we find?

We found that obesity-attributable comorbidities are associated with early mortality that leads to large decreases in life years and increases in mortality rates. The life years lost associated with obesity related diseases is more marked for younger adults than older adults, for blacks than whites, for males than females. Furthermore, the magnitude of life years lost increases with increasing level of obesity.

Using U.S. non-smoking adults aged 40 to 49 years as an example to illustrate percentage of the life years lost associated with disease caused by obesity, we found that the mean life years lost for U.S. non-smoking black males aged 40 to 49 years with a body mass index above 40 kg/m2 was 5.43 years. This translates to a 7.5% reduction in total life years lived. White males of the same age range and same degree of obesity lost 5.23 life years on average - a 6.8% reduction in total life years. For black females the numbers are: 5.04 years, a 6.5% reduction in life years, and white females they are: 4.7 years, a 5.8% reduction in life years.

Overall, diseases caused by obesity increase the chances of dying and lessened life years by anywhere from 0.2 to 11.7 years depending on gender, race, BMI classification, and age. The effect of obesity related diseases on mortality is shown for each age group in the figure below.



The epidemic of obesity in the US continues to carry a heavy burden for society 11,12, on our health care system 13,14, our businesses 15, and on our families.

References

The quick summary of our center is available through this link. "Transdisciplinary Center Approach to Examine Multilevel and Multigenerational Associations Between Obesity and Cancer". 


Over the coming months we will add updates on progress as we expand our research and translation to practice to address obesity and prevent cancer.

In our Prevention Snapshot we refer to data from a thorough analysis reported by Renehan who combined prospective cohort data separately for men (7 studies) and women (6 studies) and observed a significant increase in relative risk of 1.11 for a 5 unit increase in BMI for men 1. This meta-analysis also reported no meaningful variation in the results among the studies evaluating BMI and multiple myeloma. 

In what in many ways is a definitive study on the topic, a very large analysis of 1.46 million adults further confirms that overweight and obesity significantly increase the risk of mortality (study). The analysis by Berrington de Gonzalez and colleagues, which appears in the New England Journal of Medicine today, pooled together data from 19 prospective studies that followed participants over time - noting participant's body mass index (BMI) and keeping track of participant deaths.

Because health status and smoking status can have an impact both on weight and mortality - sick people often lose weight, and smokers are often lean and prone to dying earlier than non smokers - researchers focused their analyses on participants who were both non-smokers and healthy at the study's start. The goal was to get a truer reflection of the impact that weight could have on health.

What they found was that as BMI increased above the normal range (BMI = 18.5 - 24.9), the risk of premature death went up. Those in the overweight category (BMI = 25 - 29.9) had a 13 percent higher risk compared to those with a BMI of 22.5 - 24.9. Those in the obese category (BMI = 30 - 34.9) had a 44 percent higher risk. While those in the super obese categories with a BMI between 35 - 39.9 and 40 - 49.9 had an 88 percent increase and more than double the risk, respectively. (BMI Calculator).

As found in some other studies, there was also some increase in risk for those who fell in the underweight category (BMI = 15 - 18.4) and in the lower end of the normal range (BMI = 18.5 - 19.9). The data suggest though, that these numbers may be capturing some residual health issues, possibly undiagnosed illness which causes some of this increase in risk among the very lean. Those participants in the underweight category who were regularly active - a marker for good health - had less of an increase in risk than those who weren't active. That the risk linked to underweight largely went away after 15 years of follow-up is another indicator that pre-existing illness may be at work in the group.

Perhaps the most notable finding from the paper is a clear and sustained increase in mortality seen in folks who fall in the overweight category (BMI = 25 - 29.9). Some previous results from some big studies, such as Flegal et al, 2007, found no increase in mortality in this category, most likely because they did not exclude smokers and those with illness as the current paper did.

What this new analysis clearly shows is that maintaining a healthy weight has real health benefits. While there will always be news stories and select journal articles calling into question the true benefits of a healthy weight, this paper shows that in the face of our growing obesity epidemic, where 66 percent of the US population is overweight or obese and therefore at increase risk of pre-mature death, we need to put to rest the question of whether overweight impacts health and start to answer in ernest the question: what are we going to do about it?

Related CNiC Posts
Weight
Diet
Exercise

Related Web Resources
Obesity: Economic Burdens and Costs (Graham A. Colditz, MD, DrPH)
Harvard's Nutrition Source

This morning, I had the extreme pleasure of hearing Dr. Bill Dietz of the CDC's Division of Nutrition and Physical Activity in the Center for Chronic Disease Prevention and Health Promotion speak about Policy and Environmental Changes to Prevent and Control Obesity at the Washington University School of Medicine Grand Rounds. Dr. Dietz touched on many topics, but one that stood out to me was the focus CDC has on its list of priority strategies to address important health behaviors: increasing access to fruits and vegetables through retail stores.

I'm sure many of my fellow news junkies saw the NY Times Magazine story about Walgreens' new program to eliminate food deserts. A food desert the NY Times describes as "urban neighborhoods where there are few grocers selling fresh produce, but a cornucopia of fast-food places and convenience stores selling salty snacks (though, strictly speaking, the term can be applied to rural or suburban areas, too). Often the problem afflicts low-income areas abandoned or shunned by food businesses that focus on better-off consumers"

Food deserts are a problem that numerous non-profit and community groups have worked to tackle. Most notable is probably the Food Trust based in Pennsylvania. The Food Trust work has expanded to other states and has had some notable successes in encouraging supermarket development and expanded farmers' market programs. Perhaps it shouldn't be surprising then that when the US government announced the $400+ million Healthy Food Financing Initiative to bring grocery stores to underserved communities, it did so in Philadelphia.

Do big intiatives like this work? The general consensus is cautious optimism. Certainly having the White House behind programs like this is a big deal. But, as Marion Nestle noted, voluntary programs such as these don't always move us very far in the path to healthier communities. That businesses are seeing an opportunity here, perhaps points to some real movement (even if the cynic in me points out that this is about the bottom line for any business). I'm looking forward to seeing Walgreens provide some data on the successes (or not) of their program, something the Times article notes it has been unwilling to do so far. I'm also curious to see more data on whether these programs change fruit and vegetable intake, and ultimately rates of associated comorbidities, like obesity. Economic disparities have a big effect on food choices and the economic challenges facing families will be a big driver of our success in food access and numerous other health challenges.

That obesity had deleterious health consequences isn’t news, especially around here. Yet, we still find the results of a study out of Australia, published in Cancer Epidemiology Biomarkers and Prevention this week on weight gain and colon cancer risk compelling. Most adults experience weight gain over the course of their lives and this weight gain, even if your BMI remains within the “normal” range, can increase your risk of colon cancer. Bassett and colleagues found that each 5 kg (11 lbs) of weight gain in men significantly increased risk of colon cancer. Reports on the effects of weight gain for women are less consistent, and this report found no association.

Why might gender matter? Men and women tend to gain weight differently in adulthood. Men, in particular, tend to see a shift in body fat from the periphery to the trunk - that is, they put more weight around the middle - something called abdominal adiposity, or abdominal obesity if it gets bad enough. This central weight gain may be a stronger predictor than overall weight of cancer risk (along with other health outcomes). Abdominal obesity is associated with hyperinsulinemia, which likely plays a role in colon cancer risk. Men tend to accumulate more visceral fat.

Does this mean women are off the hook? Sadly, no – as regular CNiC readers have surely realized by now – “cancer” isn’t one disease with uniform risks. And weight gain increases risk of breast cancer in women as we’ve discussed before. So the findings on colon cancer are evidence that EVERYONE benefits from avoiding weight gain.

And since avoiding weight gain is easier than losing weight once you’ve gained it, watching weight gain is a good strategy for all of us.

Related CNiC post

Untapped benefits of physical activity

Obesity epidemic: Let's move from media attention to action

Literature cited