Obesity has reached epidemic proportions. People are fat and getting fatter, with no end in sight. Even kids are fat these days. Right? We’ve all seen the picture of the McDonald’s-eating toddler and heard the dire nightly news reports about growing obesity narrating back shots of anonymous overweight families trudging along with wedgies and short shorts. But just as the public at large bemoans the pervasiveness of the obesity epidemic, many critics are claiming the opposite: that the obesity epidemic is exaggerated and overinflated; that the “overweight” and “obese” categories are ploys by insurance companies to get more money from policy holders; that obesity in and of itself isn’t actually a health hazard. Some, like Paul Campos, are even arguing that America’s weight problem is “imaginary.”
Could this be? Am I tilting at windmills when I decry our collective weight problem?
Let’s look at the claims being made.
First, there’s the claim that the definition of obesity is arbitrary and the obesity epidemic only arose because our definition of obesity changed to include more people. According to this argument, people aren’t necessarily any heavier, but what was previously assumed to be a healthy weight has now been deemed an unhealthy weight by statistical trickery. In his 2005 book, Fat Politics, J. Eric Oliver (PDF) tells the story of Louis Dublin, a statistician for MetLife insurance in the 1940s who analyzed the connection between age, bodyweight, and death rate among MetLife subscribers. Dublin found that thinner people generally lived longer and those who maintained close to the bodyweight of an average 25 year-old lived the longest. He published a new weight chart that shifted the healthy weight threshold back, effectively making millions of Americans obese or overweight overnight. And even though he did this to predict who would die earliest and determine who should pay the most for insurance policies, not to uncover a public health threat, it caught on and formed the basis for government policy regarding obesity and health that continues today.
The controversy is in determining whether the current weight charts are based on medical observances and biological truths about the effect of certain BMIs on disease and death risk, or on corporate interests. Is a BMI greater than 25 officially overweight because research shows that people with BMIs over 25 are more likely to die or develop diabetes, heart disease, cancer, and other degenerative diseases?
This leads to the second main argument – that obesity in and of itself has never been causally linked to health problems or increased mortality.
It’s not a new one. In both Oliver’s book and The Obesity Myth, by Paul Campos, the authors try to debunk the causal connections between obesity and poor health outcomes. According to Campos, Oliver, and others like the Health at Every Size (HAES) movement, the negative health effects associated with obesity aren’t caused by the excess body weight itself, but by the inactivity, poor eating, and other metabolic factors that cause the weight gain. Obesity is just an indicator of the root metabolic dysfunctions. And it’s not even a reliable indicator, they say, since many obese people remain “metabolically healthy.” They often cite the studies that find slightly overweight BMIs to be protective against early mortality as proof.
Some of their messages resonate. Fixating solely on what the scale says while excluding how you look, feel, perform (in the gym, bedroom, and bathroom), and sleep doesn’t really work, and I have always maintained that body weight is not the ultimate determinant or even indicator of health. BMI is good at identifying obesity in large populations, but it’s less accurate on the individual level, almost to the point of uselessness. People who strength train will often have overweight BMIs but low body fat. Are they overweight? Technically, yes. But are they unhealthily overweight? Absolutely not.
But I’m not convinced the obesity epidemic is a figment of our imagination, nor do I think obesity in and of itself is harmless.
Evidence shows that body fat is an endocrine organ – it produces hormones that help control body weight and energy metabolism, as well as inflammatory cytokines. It’s not inert insulation that just sits there. It does stuff and if you have too much of it, it does bad stuff. Like:
- Body fat secretes leptin, the “I’m full” hormone. Leptin indicates “plenty” to the body, and it scales up with body fat. The more body fat you have, the more leptin you secrete, the less you eat. It’s one way our body keeps itself in energy balance, and it works pretty well – up to a point. Unfortunately, excessive amounts of body fat secrete more leptin than the body can handle, the leptin receptors become resistant to the effect of leptin, the “I’m full” message cannot be received, and hunger grows unabated. Thus, obesity often perpetuates itself by blunting the appetite-suppressing effect of leptin.
- Body fat also secretes adiponectin, an anti-inflammatory hormone involved in glucose regulation, fatty acid oxidation, triglyceride clearance, and insulin sensitivity. More adiponectin means better fat burning, favorable blood lipids, improved glucose tolerance, and lower insulin levels. Unfortunately, the relationship between body fat and adiponectin secretion isn’t like the one between body fat and leptin. The more body fat you have, the less adiponectin you secrete. That’s why the obese and overweight tend to have lower levels of the beneficial hormone.
- Body fat secretes resistin, a hormone that increases insulin resistance. Both genetic and diet-related obesity increase resistin levels, suggesting that resistin is a function of obesity and excessive body fat rather than the lifestyle factors that lead to obesity. If a bad diet and poor exercise habits increase resistin, it’s only because they also increase body fat.
- Body fat secretes inflammatory cytokines, also known as adipokines. Adipokine-derived inflammation may be causing or exacerbating the insulin resistance and other conditions often associated with obesity. Thus, obesity is inherently inflammatory.
There are also different kinds of body fat. You’ve got subcutaneous fat, visceral fat, and brown fat. Visceral fat (the fat that surrounds organs and concentrates in the abdominal area) contains more inflammatory cells that secrete inflammatory cytokines. It’s more metabolically active, more insulin resistant, more dangerous than subcutaneous fat, which is more stable and less inflammatory (but still not harmless!). Meanwhile, brown fat actually promotes the oxidation of other kinds of body fat. It’s how babies keep warm without the ability to shiver, and new evidence reveals that it plays a large role in adult metabolism, too; adults with the most brown fat have lower fasting glucose and weigh less. If you’re going to say that obesity is healthy or imaginary, you have to account for the functional differences between subcutaneous, visceral, and brown fat.
As to the arbitrariness of BMI interpretation, okay. That’s true. It wasn’t based on the most rigorous of data analysis. Even so: how we interpret BMI has changed, but how we measure BMI has not. Say there’s a guy with a BMI of 26 in 1985. You put him in a DeLorean DMC-12, tell him to hit 88 MPH until he catapults into the year 2014, and then recalculate his BMI. It’s still going to be 26. The rate of people with high BMIs indicative of overweight/obesity/whatever you want to call it has not remained static. Unless you’re positing that corporate interests corrupt the calculation of BMI, bodyweight has increased. The data is clear (PDF). Value judgments about those BMIs are another thing entirely, but that doesn’t negate the fact of the matter: people are getting larger.
Besides, BMI isn’t the only way to measure obesity. It’s not even a particularly effective way. If we look at every other measurement of obesity available, it’s increasing. Waist circumference (an arguably better marker than BMI for predicting heart disease mortality) has been going up. Abdominal obesity – the most dangerous kind (or the kind that’s most strongly associated with poor health outcomes, if you’re Paul Campos) - is increasing and has tripled since the 1960s. And although this is anecdotal and thus inadmissible in the court of Science Based Medicine, just taking a look around next time you’re out at a mall or an amusement park will tell you that obesity remains an issue.
And the common co-morbidities of obesity and overweight have been increasing in incidence, too. Non-alcoholic fatty liver (even in teens), type 2 diabetes, obstructive sleep apnea (which is strongly correlated with body fat percentage, especially abdominal body fat), most cancers, and many other conditions associated with obesity are all rising.
So there you go. People are getting bigger. They’re gaining belly fat. Common obesity co-morbidities are skyrocketing; even if people are living longer, they’re feeling worse. Maybe those morbidities are just associated with obesity, not caused or exacerbated by it. That’s fine. Call it what you want, as long as you acknowledge that a problem exists.
Because in the end, losing excess body fat just works. Whether it’s the inherent healthiness of the steps you take to lose the weight, the normalization of leptin, resistin, and adiponectin levels and the reduction in fat-derived inflammatory cytokines that comes from shedding excess body fat, or both, you’re healthier. And a bit leaner.
Let’s imagine for a moment that the excessive accumulation of adipose tissue (obesity) is completely innocuous. Maybe obesity and its related maladies merely have common causes, like inactivity or a bad diet, and don’t interact with each other at all. Maybe body fat is the body’s way of dealing with the true offender and obesity is just a reliable indicator of poor health, diet, and exercise habits (I suspect this is partially the case). Assuming all that is true, what changes? What are you doing differently to improve your health? You’re losing body fat. If getting rid of the obesity (through changing your diet and modifying your activity patterns and getting better sleep and reducing stress) makes you healthier, the primary cause doesn’t matter. Only results do. You don’t ignore the smoke alarm just because it’s not the cause of the fire.
That’s my take on the situation, folks. What about you? Let’s hear yours in the comment section.