Are we really heading in the right direction with childhood obesity? (and a fun lesson in epidemiology)

I saw some very encouraging headlines last week about childhood obesity, not the least of which came in the NY Times:

"Obesity Rate for Young Children Plummets 43% in a Decade"

I've also come across graphs like this one, which support the narrative (Note this graph is for obesity only, i.e. 95th BMI percentile - More on the distinctions later).

 

Whenever I see headlines like this though, my first instinct is to immediately go to the actual study, which in this case was published in the Journal of the American Medical Association (or JAMA). After looking at all the data, the story is often MUCH more nuanced than gets spun in the media. This study was no different. More on this in a second.

The other thing that generally happens around these type of epidemiological studies is that speculation abounds about what CAUSED the particular change. These type of prevalence studies essentially take a static picture of a particular health concern (in this case elevated body mass index - the common marker used to assess overweight and obesity) within a given population (a nationally representative sample of children in the US ages 2-19 for this study). If the methods are consistent over time, you can then compare what today's picture looks like compared to the picture, say five years ago. But that's all you can do - compare the pictures. What often happens, of course, is commentators begin to offer different theories as to what caused the changes in the pictures, like in this Washington Post blog. It's important to remember these are just speculations. These studies were never designed to actually assess this question of causation.

We also see the unfortunate occurrence of over-generalization. This is when the findings of a particular population are extrapolated to other populations (this is a big no-no in epidemiology), like in this article that references "youth-related" obesity, but cites the decline found in 2-5 year olds (i.e. children not youth). 

Ok, let's get to the data.

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The following are a series of graphs I put together using the same NHANES data published in the most recent JAMA article, but instead disaggregated by race. These charts tell a much more nuanced story, particularly as there is a significant race/ethnicity component to obesity in the US. Another modification I made was to look back to 1999-2002 to provide additional context on trends (instead of 2003, which the above graph used). The reference point for trends provides a lot of valuable information and shapes how the results are framed.

Let me show you why.

These are prevalence data for overweight and obesity (measured as a BMI of greater than or equal to the 85th percentile and 95th percentile respectively) for several different age groups disaggregated by race/ethnicity.

Overweight and Obesity (85th percentile), 2-5 years old

Obesity (95th percentile), 2-5 years old

*You'll notice from this second graph that an interesting story emerges, one that is masked when only looking at aggregated data. Though there are some significant declines among certain populations (most notably non-Hispanic whites), there is a steep upward trend for Hispanics.

Overweight and Obesity (85th percentile), 6-11 years old

Obesity (95th percentile), 6-11 years old

*Here, I think it's important to think about the reference point, especially in the first graph for overweight and obesity among 6-11 year olds. Though a little progress here and there, all categories have a higher prevalence in 2011-12 than in 1999-2002. The graph would tell a different story if the reference was 2003-04, as in the first graph in the article. We also see another age group where prevalence of overweight and obesity increased most recently among Hispanics (in addition to non-Hispanic whites).

Overweight and Obesity (85th percentile), 12-19 years old

Obesity (95th percentile), 12-19 years old

*Again, we see a similar story to the 6-11 age group. There is considerable variation when looking across race. In fact, we see an overall increase from 1999-2002 to 2011-12 when looking at all races within this age category.

Take Home Message

My take of the data is that it's a much more nuanced story than what's being portrayed. Yes, there are some positive trends. But these are within specific age groups and looking at specific markers (i.e. 85th percentile of BMI vs. 95th percentile). Looking at what happens later in childhood and into adolescence, the trends in obesity aren't as favorable. In a sense, gains early in life (2-5 years old) could be offset by what's occurring in some of the older age groups. And, just because a national-level trend is positive (all kids of a particular age), doesn't mean it's positive for all the different sub-groups (in this case broken down by ethnicity) that make up the national average.

References

All data in the blog were produced using the following:

Hedley AA, et al. Prevalence of Overweight and Obesity Among US Children, Adolescents, and Adults, 1999-2002. JAMA. 2004;291(23):2847-2850.

Ogden CL, et al. Prevalence of High Body Mass Index in US Children and Adolescents, 2007-2008. JAMA. 2010;303(3):242-249.

Ogden CL. Prevalence of Childhood and Adult Obesity in the United States, 2011-2012. JAMA. 2014;311(8):806-814.


Disclaimer: The views in this article are my own and don't necessarily reflect those of my employer or my employer's clients.

Obesity the disease: Is it really about health?

The media and blogosphere lit up after the recent American Medical Association annual meeting.

Why?

The prestigious, 165 year-old organization of 225,000 doctors voted to recognize obesity as a "disease." Yup, let me say it again, according to the AMA, obesity is now considered a disease.

Now, of course, there are fairly convincing arguments on both sides of the spectrum (here is an interesting compilation of arguments from members of the Obesity Society). The popular obesity blog Weighty Matters lays out a pretty good listing of reasons against obesity as a disease. Interestingly, the article starts off by applying the common definition of disease, and seeing if obesity fits - "A particular quality, habit, or disposition regarded as adversely affecting a person or group of people."

At first glance this seems to make a lot of sense. Obesity is a quality or disposition that adversely affects an individual and society (a prime example being the health care costs associated with obesity).

This is the argument taken by Lee Kaplan, director of the Obesity, Metabolism and Nutrition Institute at Massachusetts General Hospital, associate professor of Medicine at Harvard Medical School, and chairman emeritus of the Campaign to End Obesity:

"The simple fact is that obesity is a disease, a chronic, frequently progressive, and rarely remitting disorder that triggers an additional 65 or more other conditions ranging from arthritis and sleep apnea to many forms of cancer."

On the other hand, will the AMA's announcement simply medicalize the issue rather than addresses the miriad of factors that influence it. Public health expert David Katz makes this point when illustrating the irony of the AMA’s announcement and the recent introduction of the first FDA-approved obesity drug into the market. This obviously begs the question of who really stands to benefit: those who suffer from obesity or big pharma? Dr. William Davis, the preventive cardiologist and best-selling author, answers in pretty simple terms:

"To the system, you are worth more obese than slender. You are worth more diabetic than non-diabetic. And you are worth more as a wheat-eater than as a non-wheat eater."

One might go as far as to say that this is a classic example of "disease mongering" - a phenomenon described by Lynn Payer as the ability to control the destinction between health and disease, thereby allowing drug companies to determine the size of their own markets. From the enlightening book The Bottom Line or Public Health,

"Since disease is such a fluid and political concept, the providers can essentially create their own demand by broadening the definition of diseases in such a way as to include the greatest number of people, and by spinning out new disease."

It wasn't long after the AMA's announcement that its implications were already being seen. Only a few days later, Members of Congress introduced the Treat and Reduce Obesity Act (H.R. 2415/S.1184), a bill that would  allow Medicare coverage of prescription weight-loss drugs.

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The Wall Street Journal importantly points out that even if obesity is characterized as a disease, there is still a pretty big grey area in terms of how to actually measure and track obesity trends. Traditional "diagnosis" of obesity has been using the imprecise Body Mass Index, which is simply weight divided by height. One can easily guess why this can be a challenge -  just think of a fairly fit athlete with good dose of lean muscle mass. Unfortunately, BMI doesn't distinguish between fat mass or muscle mass, which, of course has some severe limitations. Other research has shown (see here) waist circumference to be a much better predictor of obesity-related health risk and subsequent health costs (see here).

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Might characterizing obesity as a disease actually be counterproductive to prevention efforts? A new study released a few weeks ago found that if parents discuss weight issues with their children they are in turn more likely to diet, use unhealthy weight-control behaviors, and engage in binge eating. By classifying obesity as a disease, won't doctors be more apt to discuss it in terms of "treatment" options for their condition - i.e. in the context of weight (remember how obesity is classically measured - BMI = weight/height)? And, my fear, is that by framing conversations between health providers and children/adolescents and their parents in terms of weight alone, children and teens might turn to some of the same negative dietary behaviors mentioned in the study.

The current President of the AMA doesn't think so, and recently defended the organization's decision.
She makes the argument, "Recognizing obesity as a disease will encourage a dialogue between patients and physicians to determine which behavioral, medicinal or surgical options may be right for them." But an honest dialogue between physicians and patients about options is only as useful as doctors are informed and able to accurately communicate the range of options.

Take for example nutrition.

Now, I think doctors are good at a lot of things, but offering nutrition advice (i.e. behavioral option) is not one of them. And medical schools themselves agree with this statement. A 2010 survey found that among 105 accredited U.S. medical schools, only 26 (25%) required a dedicated nutrition course! In other words, medical students (or our nation's future doctors) from three out of four U.S. medical schools received ZERO training on nutrition. The average contact hours of nutrition instruction medical school students received was 19.5 hours, and this was about 3 hours LESS than the average time from 2004.

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My biggest fear, however, is that by placing the emphasis on obesity we neglect the underlying physiological processes contributing to weight-gain in the first place. Some research has already suggested that the link between obesity and shorter life expectancy may not be as clear cut as we once thought (i.e. being obese might not be the real issue. More on this below). The research was published earlier this year in the Journal of the American Medical Association and found that "Grade 1 obesity overall was not associated with higher mortality, and overweight was associated with significantly lower all-cause mortality." (Yes, this is pretty ironic coming from the academic journal of the same professional organization that just a few months later deemed obesity as a disease.)

Dr. Peter Attia made a strong and eloquent case at this year's TEDMED conference about why obesity might not be the real issue. What if we have the causality backwards? What if obesity doesn't lead to issues of diabetes and metabolic syndrome, but the real issue (and whether our body stores or burns fat) has everything to do with insulin - i.e. the hormone at the crux of diabetes and metabolic syndrome? What if obesity is just a by-product of the metabolic firestorm caused by chronically consuming excessive sugar, starches, and refined carbohydrates?

What do you think - was the AMA's announcement beneficial or harmful?

Comparing obesity trends in the U.S. with other countries

Last week PBS Newshour published an interesting article reporting on obesity trends among some of the major developed countries around the world, including the United States. Using an interesting resource by the Organization for Economic Co-operation and Development (an organization of 34 industrialized countries, including the U.S) called the Better Life Index, the tool below lets you explore and compare obesity trends across different OECD countries.

Endurance Sports and Heart Health (Part II): What are the benefits?

This is the second part in a series of posts on endurance sports and heart health.

2,466,115,200. That's how many times my heart will beat if I live as long as the average American is expected to (78.2 years). (My wife says it better beat for longer.) My resting heart rate is about 60 beats per minute. That's a fascinating number to think about. For almost eight decades my heart will supply my entire body (and itself) with the oxygen it needs to survive, and never stopping. 

When it comes down to it, the heart is a relatively simple organ - essentially a four-chambered pump with some tubing going into it and coming out of it. But of course the devil is in the details. Over the course of more than 2 million beats, there is a lot of opportunity for things to go wrong, and many times these things are the result of accumulated issues over time.

As I discussed in the first part of this series, with endurance exercise, there is a fine line between performance and pathology - something referred to as the "grey area" in the scientific literature. There are risks when it comes to endurance sports. But risks can be managed and risks must also be viewed in the context of benefits (it's all about optimizing). 

In this post I discuss some of the benefits of endurance sports and regular exercise, particularly from a physiology perspective, as well as a public health standpoint. But I close with some cautions about maximizing exercise while neglecting other areas of daily life that contribute to heart disease and heart issues.

Popularity of Endurance Sports is Increasing

Endurance sports, such as half-marathons, marathons and triathlons, are becoming more and more popular. The previous post in this series showed the increasing level of participation in USAT-sanctioned triathlon events. Half-marathons and marathons held in the U.S. show a similar trend. Not only are there more races, but more people are participating. For example, according to Running USA, a non-profit that tracks trends in U.S. distance running events, the number of marathons in the U.S. more than tripled between 1985 and 2011, from 200 events to 720 events.

Active.com, an online community for sports and event registration hub for a variety of activities (including running, cycling, triathlon, and more), revealed similar increases based on race registrations between 2008 and 2010. During these three years, marathon registrations increased 203%; half marathons rose 154%, 10K events rose 155% and 5K events rose 144%.

Why is This a Good Thing from an Individual Health Perspective?

Your heart is a muscle, and like other muscles, it responds to stimuli like exercise. It can grow stronger and increase in size similar to other muscles in our body after periods of exercise. And generally (and up to a point), the more exercise, the stronger, more efficient, and sometimes larger the muscle. Endurance activities markedly improve the efficiency of your heart, increasing stroke volume (or the amount of blood pumped by the heart with each beat) and thereby decreasing the number of overall beats needed.

Other markers of heart health have also been positively linked with endurance exercise, such as lower blood pressure and increased HDL cholesterol.

There is also evidence to suggest that exercise plays a strong role is energy partitioning, or the type of energy (such as carbohydrates or fat) our body preferentially burns for fuel. One study of 55 years old women found a more than 9% increase in energy derived from fat after 12 weeks of endurance exercise training.

The weight-bearing movements of regular exercise and strength training support bone health and improve longevity, particularly as people age. Exercise is also associated with lower stress levels, higher energy levels, and overall positive mental health.

Not a bad list of benefits.

Why is This Essential from a Public Health Standpoint?

Physical inactivity is becoming a new norm and the trends don't look promising. A recent review from researchers from the University of North Carolina looked at trends of metabolic equivalent hours (just a fancy way to show the amount of exertion by your body doing different activities) from 1965 to the present, and also projected trends through 2030. Between 1965 and 2009, MET-hours per week decreased by about half (235 to 160), and they are projected to decrease to roughly 126 by 2030. You can see the trend in the graph below, which traced MET-hours in several different areas, such as physical activity during work, transport, domestic activities, and leisure time. The black line is the average hours per week of being sedentary.

The rising trend from 2010 to 2030 represents one of the major public health challenges we face. 

 

What These Trends Don't Tell Us  

Even though registration and participation levels in endurance activities, such as triathlon and marathon, are increasing for a range of age groups, a couple things to remember.

First, this is still a relatively small proportion of the overall U.S. population, which is almost 315 million. From a sports, competition, and individual health perspective, increasing participation is a great thing. For people like myself, it provides a great opportunity to continue competing, setting and working towards new individual goals, staying in good overall health (though my third point mentions another counter-argument to this), and traveling to new and interesting places. However, one must keep this all in perspective that we're still talking about a fairly exclusive cohort of people.

Second, inequalities, particularly in regards to access, are major issues. Opportunities to participate in physical activity pay huge dividends with individual physical and mental health, population health, and create millions of dollars of health care cost savings annually. But, not everyone can afford a gym membership; or can safely walk to a park; or can spare the $120 marathon registration or the extra 30 minutes a day to train. The challenge is to celebrate record numbers of people taking on the endurance challenges of running, triathlon, cycling, etc, but to also ensure environments are conducive to regular physical activity for everyone.

Third, all the effort put into exercising everyday could be for naught if you spend hours sitting for the rest of the day. A recent review examining the link between sedentary time and diabetes, cardiovascular disease and cardiovascular and all-cause mortality in adults older than 18 years of age found that "higher levels of sedentary behavior are associated with a 112% increase in the RR of diabetes, 147% increase in the risk of cardiovascular disease, 90% increase in the risk of cardiovascular mortality and 49% increase in the risk of all cause mortality." Even more frightening are the results from a recent National Health and Nutrition Examination Survey. The study looked at almost 5,000 adults 20 years of age or older and found "Independent of potential confounders, including moderate-to-vigorous exercise, detrimental linear associations of sedentary time with waist circumference, HDL-cholesterol, C-reactive protein, triglycerides, insulin, HOMA-%B, and HOMA-%S were observed." (emphasis added) This essentially is saying that even if someone exercises in the morning, and the rest of the day is spent sitting, this could have a detrimental effects on risk factors - high levels of triglycerides, higher inflammation, higher waist circumference (a fairly good measure for dangerous visceral fat), etc - for heart disease and other chronic diseases.

So, I come back to this theme of optimizing. Sure there are a lot of health benefits to exercise and endurance training. But at the same time, if you're trying to maximize in this area of your life, and neglect other things (such as diet, stress, amount of time sitting during the day, etc), are you really optimizing for better overall health?

Let me know your thoughts and post a comment below.