the Natural Condition

Being overweight is bad for your health, right? With all the talk of the American obesity epidemic and the consequent rise in diabetes and associated ailments, combined with the fact that cardiovascular disease is known to be the leading killer in America and is exacerbated by lack of exercise, most people assume that excess poundage will lead to a shortened life span. While the information I am about to divulge is not new, I would like to summarize the findings of a 2005 study that, very shockingly, discovered a decrease in the death rate for “overweight” persons.

In 2005, JAMA published an article by Flagel et al. of the National Center for Health Statistics (a division of the CDC) and the National Cancer Institute entitled “Excess Deaths Associated With Underweight, Overweight, and Obesity.” The authors sought to answer broad questions about the impact of weight (BMI) on mortality. They used 3 of the National Health and Nutrition Examination Surveys (NHANES), which comprise data on over 35,000 people dating as far back as 1971. They grouped patients into 4 categories of interest, with one control, all based on BMI. They used the national standards for BMI classification:

1. <18.5 : Underweight
2. 18.5 - <25 : Normal (control)
3. 25 - <30 : Overweight
4. 30 - <35 : Obese
5. ≥35 : Morbidly Obese

When performing their analyses, each group was controlled for known confounding factors to mortality, such as smoking. The table below outlines their findings for relative risk of death by age group and BMI. A RR<1 means that a population is at less of a risk for dying than the Normal-weight group, RR>1 means they do worse.

^{Relative risk of death by age group and BMI. Image courtesy of JAMA.}

What we see in this table is that both the Obese and Underweight cohorts have substantially higher relative risks than Normal-weight individuals, and more markedly so in younger age groups. The big, and unanticipated, anomaly is the Overweight cohort, which exhibited a relative risk <1 in every case. Flagel et al. then used these relative risks, in conjunction with US prevalence data on BMI, to yield estimations of excess deaths due to weight … or, for the Overweight category, lives saved.

^{Annual excess death estimates by cohort, paneled by BMI category. Image courtesy of JAMA.}

If that last line about ‘lives saved’ for being overweight chaffed you: it chaffed me, too, so let’s dig deeper. While I am not a statistician, I did read their Methods thoroughly, but still do not quite understand how they reached their estimates for excess death, which incorporate the relative risks. One seemingly important point about the relative risks for the Overweight group (above table) is that, while each estimate fell below 1, the 95% confidence intervals for every Overweight RR overlapped 1. Because a relative risk of 1 never fell outside of their confidence band for an alpha of .05 for any age group, how could they reach the conclusion that there is always a negative number of excess deaths (positive number of lives saved), “–86 094 deaths; 95% CI, –161 223 to –10 966″¹? They say that the uncertainty of the relative risk is propagated in the excess death estimate, but as I just outlined, the result does not seem coherent.

Their findings are, nonetheless, suggestive that having an ‘Overweight’ BMI may confer additional years of life, although “bias may also result from failure to control for unknown confounders that are associated with body weight and mortality,”¹ as the authors indicate. I should mention that nowhere in the paper do the authors esteem their finding of a decreased relative risk for ‘overweight’ BMIs. In a way, they elegantly dismiss that peculiar result, stating simply that “Overweight was not associated with excess mortality.”¹

In any case, the more important fact to glean from this discussion is that any large deviation from a normal BMI is associated with increased mortality. In response to the Flagel study, Thomas Hoerher, PhD wrote, “although mortality is an important measure of the burden of a disease, it is not the only one. Obesity also has significant impacts on morbidity, health care costs, and quality of life.”² Obesity is not healthy, and 112,000 excess death per year is a serious matter.

Footnotes/Further Reading:
(1) Excess Deaths Associated With Underweight, Overweight, and Obesity. JAMA. 2005.
(2) Controversies in Obesity Mortality: A Tale of Two Studies. RTI-UNC Center of Excellence in Health Promotion Economics. 2006.
(3) CDC Downscales Mortality Risk From Obesity, USA. MedicalNewsToday.com. 2005.

A startling map of obesity in America, and how is has increased exponentially in the last 20 years:

CNN’s Map of Obesity in America

Epidemiologists set the bar for obesity at a BMI of 30. BMI stands for “body mass index,” and it is a measure of divergence from optimal weight. To calculate a BMI value, you divide an individual’s weight (kg) by the square of their height (m²).⁽¹⁾ To put a BMI of 30 into perspective, a 5′5″ female would weigh 180lbs, and a 5′10″ male would weigh 209lbs. I gave the average heights for adult men and women in the US, but, in fact, the BMI calculation is independent of sex, body frame, musculature, etc. It is, therefore, a rather crude metric for estimating obesity rates, as the only determining factors are height and weight. I.e., you could be super jacked, but have a BMI that technically places you in the overweight range.⁽²⁾ However, as the ratio of jacked:fat in America is approximately 0.0001, BMI is probably a reasonable indicator of America’s waistline, when averaged over a population.

Well enough about BMI. The bottom line is that America is getting extraordinarily fat, and the obesity epidemic is spreading Read the rest of this entry »

High Fructose Corn Syrup (HFCS) is one of the most ubiquitous sweeteners in modern foods. While it receives much press for its prevalence in soft drinks, it also sneaks its way into some foods you might not expect: ketchup, dubious “juices,” pizza, yogurt, saltine crackers, and that overpriced vanilla latte you’re drinking.(4) Did you catch that I mentioned corn sweeteners in your saltine crackers? Gross? Well, at least a little weird. That one alone might make me think twice, but there’s more to the story.

Food manufacturers put HFCS in their foods because it is as sweet or a little sweeter than traditional sugar (sucrose), it extends shelf life of foods (1), and it is cheap. Anyone who has ever driven through the non-coastal US states and finds nothing but endless fields of corn might question where all that corn goes, because nobody eats the stuff 5 times-per-day. The answer is that, while most corn Read the rest of this entry »

After spending a day fasting this past weekend, I’m interested in learning more about the idea of a ‘calorie-restricted’ diet. Basically, the idea is that by cutting back the amount of calories one ingests — say, by reducing by 1/3 — while remaining nutritionally nourished, the organism will optimize bodily resources, which can lead to a longer, healthier life.

Sound too good to be true? … it probably is. Although, from the little that I’ve read, this concept has been tested in several organisms, among which are the housefly drosophila, yeast, and, most promisingly, primates. With the exception of the housefly, studies have demonstrated that the organisms tend to lead healthier, and thus longer, lives, which makes a very appealing case. Biologically, it is reasonable to think that Read the rest of this entry »