Weight Wisdom: Avoid Extremes, But Being “Over” May Have Benefits

A new CDC-released study by National Center for Health Statistics’ Dr. Katherine Flegal and colleagues (here) confirms results from her groundbreaking 2005 report (here): compared with people of normal weight (BMI = 18.5 to less than 25), those who are overweight (BMI greater than 25 but less than 30) have a lower mortality rate.  Higher mortality rates are seen with obesity (BMI greater than 30) and underweight (BMI under 18.5).    

Applying weight-based mortality rates to the U.S. population, Flegal estimated in 2005 that overweight resulted in 82,094 fewer deaths, and a significant number of excess deaths were associated with obesity, a (n = 111,909) and underweight, (n = 33,746). 

As I noted in this blog five years ago (here), Flegal’s conclusions are consistent with those of many other scientific studies. 

I have long had a professional interest in population research on weight and health. In 2004, I published the first study to show that Swedish men who quit smoking by switching to snus avoided the weight gain usually seen with smoking cessation (abstract here).  In 2015, my research group analyzed data from the National Health and Nutrition Examination Surveys to demonstrate that changes in population smoking do not contribute significantly to changes in population overweight and obesity.  (BMC Obesity article available here).

The impact of weight on life expectancy is clear: Those who are underweight or severely obese are at risk of dying prematurely, while mere overweight is associated with a lower mortality rate.

Smoking Cessation: Minimal Impact on Weight

The association of tobacco use and body weight has long been a matter of concern.  In 2004, I collaborated with Swedish investigators to publish the first research on whether switching from cigarettes to smokeless tobacco blunts some of the weight gain normally seen with quitting via abstinence (abstract here, blog post here). 

We found that Swedish snus users and smokers who switched to snus gained no more weight than nonusers (average gain of around 7 pounds over 9 years).  In contrast, the big gainers in our study were smokers and snus users who completely abstained from nicotine and tobacco.

Numerous studies have documented that smokers weigh less than nonsmokers, and smokers who quit add pounds.  Since the 1970s, there are fewer smokers and more former smokers in the U.S.  For example, in 2010, only 19% of the adult population were current smokers (44 million), while 22% (49 million) were former smokers.  Did changes in population smoking contribute significantly to changes in population overweight and obesity?  The answer is no.

My University of Louisville colleague, research economist Nantaporn Plurphanswat, and I explore this question in a research article published in BMC Obesity (available here).  We used data from the National Health and Nutrition Examination Surveys (NHANES) for the years 1999 through 2012. 

Our analysis used body mass index (BMI), a measure of weight that accounts for height.  Conventional BMI categories are underweight (BMI < 18.5), normal weight (18.5 to less than 25), overweight (25 to less than 30) and obese (30+).

Consistent with previous studies, we found that smoking was associated with lower BMI among both men and women.  In addition, being a smoker increased the probability of being normal weight by 12% and reduced the probability of being obese by 13% among men; the magnitudes for women were smaller, +7%  for normal weight and -8% for obesity.

We noted that women with higher education had significantly lower BMI than those with less education; this relationship was not seen among men.  Marriage was associated with higher BMI among men, but lower BMI among women.

In a positive finding for men, we found no difference between never smokers and former smokers in terms of being in particular BMI categories.  However, women were shown to be more prone to weight gain.  Women who were former smokers had lower probability of underweight (0.2%), normal weight (2.3%), and overweight (0.4%), but had higher probability of obesity (2.9%). 

No one should be dissuaded from quitting cigarettes, especially when there are many smoke-free options like snus and e-cigarettes that might obviate any weight gain.

Overweight and Low Mortality

Last week the Journal of the American Medical Association (JAMA) published a meta-analysis documenting that being “overweight was associated with significantly lower all-cause mortality.” (here).  The study was authored by Dr. Katherine Flegal of the U.S. Centers for Disease Control and Prevention (CDC) and colleagues at the National Cancer Institute and the University of Ottawa. 

 

This post will focus on the study’s scientific findings and the reaction to same, which is not dissimilar to the research and backlash surrounding tobacco harm reduction.

Dr. Flegal and colleagues conducted an extensive search for population studies reporting all-cause mortality according to categories of the body mass index (BMI), which is weight in kilograms divided by height in meters squared.  They used the following standard categories: 

Table 1. BMI Ranges for Weight Categories in the Flegal Meta-Analysis
BMI Range	Weight Category
Under 18.5	Underweight
18.5 to less than 25	Normal
25 to less than 30	Overweight
30 to less than 35	Grade 1 Obesity
35 to less than 40	Grade 2 Obesity
40+	Grade 3 Obesity

 

Dr. Flegal’s literature search initially identified 7,036 articles, of which 97 met the criteria for their study, which included adequate adjustment for age, gender and smoking.  The results were reported as hazard ratios (HRs), which are similar to relative risks.

Table 2. Hazard Ratios (HRs) for All-Cause Mortality According to Weight Categories in the Flegal Meta-Analysis
Weight Category	HR (95% Confidence Interval)
Underweight	Not Reported
Normal Weight	Referent Group
Overweight	0.94 (0.91 – 0.96)
Grade 1 Obesity	0.95 (0.88 – 1.01)
Grade 2-3 Obesity	1.29 (1.18 – 1.41)
All Obesity	1.18 (1.12 – 1.25)

 

 

The major finding is remarkable: Overweight people had a LOWER risk of mortality than people of normal weight.  In addition, Grade 1 obesity (up to BMI < 35) was also associated with lower mortality risk, although this was not statistically significant.  

The results run counter to the dominant public health message that overweight and obesity are killers, which is why the study was immediately denounced by many.  As Christopher Snowdon pointed out (here), extensive media coverage of the attacks gave credence to the notion that the analysis was flawed and unreliable.  Walter Willett, professor of public health at Harvard, declared: “This study is really a pile of rubbish and no one should waste their time reading it.” (here). 

This high-profile assault is similar to that which has been waged against tobacco harm reduction findings over a 20-year period.  In the 1990’s, Philip Cole and I published numerous scientific articles on the gaping difference in health risks associated with smokeless tobacco use and smoking.  We were sometimes ignored and often reviled; ad hominem attacks routinely obscured our important findings.

 

I have long had a professional interest in population studies of weight and health. In 2004, I published the first and only study showing that Swedish men who quit smoking by switching to snus avoided the weight gain usually seen with smoking cessation (abstract here).  My research experience provides some insights into the Flegal/CDC study.

Why are overweight people at less risk of dying than those of normal weight?  It’s possible that the normal-weight group included people who had lost weight because they were ill and were close to death, thereby raising the death rate in the reference group to which all other categories were compared.  In other words, an artificially higher death rate in the normal-weight group resulted in an artificially lower rate among overweights.  Although this is one of the more common criticisms discussed in the media, it is not likely to be a major factor, because the vast majority of the normal-weight population are healthy.

A more likely explanation for Dr. Flegal’s surprising result is that many in her “overweight” population belong in a properly defined “normal” weight category.

In my weight research I had to establish BMI categories.  A literature review revealed that major health organizations had changed the definition of overweight.  Up to the late 1990s, researchers had defined overweight as a BMI of 27+, which meant that normal weight went from 18.5 up to 27.  Dr. Flegal agreed with this definition, as she published a study using this classification in 1994 (here).

 

For reasons that I was never able to pin down, the definition of overweight changed in the late 1990s to a BMI of 25+.  Suddenly, people with a BMI from 25 to 27, who were previously normal weight, were now overweight.  The prevalence of overweight skyrocketed.

Since the newly-classified overweights continued to die at normal-weight rates, this reclassification might help explain Dr. Flegal’s finding of low mortality in the overweight category. 

 

One unresolved problem with Dr. Flegal’s analysis is that she defined three distinct obesity categories (1, 2 and 3 in Table 1), but then combined the mortality results for the highest two categories, and failed to report any results for the underweight category.  These are important omissions which Dr. Flegal needs to explain.

  

Despite these issues, CDC scientists should be commended for publishing this profoundly important finding: Compared with normal-weight individuals, overweight and slightly obese people have LOWER mortality.  It’s a shame that their colleagues at the CDC Office of Smoking and Health aren’t equally forthcoming about the minuscule risks for smokeless tobacco use.  For example, the first entry on the smokeless tobacco fact sheet from the CDC (available here) is - inexplicably – a webpage for gutka, a southeast Asian tobacco product that is rarely used in the U.S.  The rest of the CDC document conflates information regarding the health risks from smokeless tobacco use with those from smoking.

Like tobacco use, overweight and obesity are the objects of revulsion among some health advocates.  Scientific evidence, however, clearly shows that overweight or minimally obese people have lower mortality risks than those of normal weight, placing them at risk only for misguided, unscientific public health interventions like fat taxes (here) or soda restrictions (here).  Like tobacco users, the overweight and obese deserve health policies based on scientific facts, not fanaticism. 

Weight! Quit Smoking Without the Gain

It is well established in the scientific literature that smokers generally weigh less than nonsmokers, and that smokers who quit are at risk for weight gain. A recent article in the journal Science (abstract here) reported that nicotine activates specific nerve cells in the section of the brain called the hypothalamus. This interaction may be responsible for decreased appetite; it is different from nicotine’s trigger of reward and satisfaction in the brain. This complex research was conducted in mice, so the results will need confirmation in human studies. Still, they substantiate two dreaded downsides to quitting smoking: the loss of the powerfully rewarding and satisfying activity, and the gain of unwanted pounds.

We already know that switching from cigarettes to smokeless tobacco keeps smokers satisfied while giving them almost all of the benefits of complete tobacco/nicotine abstinence. But does switching keep the weight off?

In 2004, I published the first and only research article answering this question (abstract here). Along with colleagues from Umeå University in Sweden, I used a World Health Organization dataset to evaluate weight gain among nearly 3,000 men in Northern Sweden.

Weight Gain Over Nine Years Among Men in Northern Sweden
Tobacco Category	Average (lbs)
Nonusers (Referent group)	7.0
Smokers	5.1
Smokers who quit completely	15.0*
Smokers who switched to snus	7.9
Snus users	6.8
Snus users who quit completely	11.2*
*significantly elevated compared with nonusers

The big gainers were smokers and snus users who became completely abstinent from nicotine and tobacco. But snus users and smokers who switched to snus didn’t gain any more weight than nonusers. This is important news for smokers who are concerned about putting on pounds when attempting to quit smoking.

I also noted that the rate of overweight at the start of the study was 32% among those who didn’t use tobacco, 29% among smokers, and 42% for ex-smokers. These percentages are somewhat lower than other reports because our group defined overweight as a body mass index (BMI) of 27 or higher. The standard definition of overweight starts at a BMI of 25. For more information about BMI, go to this website at the federal National Heart Lung and Blood Institute.

Fear of gaining weight should not deter smokers from quitting. Research shows that a switch to smoke-free tobacco can leave them healthier with no added pounds.