Is Obesity Really the Killer It’s Made Out to Be?


If obesity is really unhealthy, then people living in larger bodies should be more likely to die than thinner people.  Are they?

Biostatistician Katherine Flegal reviewed over 140 studies to answer this question (Flegal, 2013).  What she found may surprise you:

  • People in the ‘overweight’ category (BMI 25-30) had a slightly lower risk of death than those in the ‘normal’ weight category.
  • People in the ‘obese’ category (BMI 30-35) had an equal risk of death as people in the ‘normal’ weight category.
  • People in the ‘obesity classes II and III’ (BMI > 35) only had a greater risk of death if they were under the age of 65.  Their risk of death was 1.3x greater than people in the ‘normal’ weight group.  (To put that number in perspective, the risk of developing lung cancer is 30x greater among people who smoke compared to people who do not smoke.)

A number of other studies found similar results (Grabowski 2001, Steersman 2009, Oprana 2010, Tamakoshi 2010, Flegal 2005, Janssen 2007, Lantz 2010, Toriano 1996; see also:  Bacon 2011).

Correlation vs. causation

The next question is: what is responsible for this slightly higher risk of death in individuals with BMIs > 35? Is it excess body fat, or could another factor actually be responsible?

In research, confounding variables make there appear to be a causal relationship between two variables, when in fact there is not. For example, having more wrinkles is associated with a higher risk of death, but older age is actually responsible for this risk, not wrinkles. The older you are, the more wrinkles you get. Using wrinkle creams will not reduce your risk of dying, because it won’t make you younger.  Older age is a confounding variable for the relationship between wrinkles and dying.

Having extra body fat may not be a true mortality risk.  Other confounding variables may actually be responsible.  People who are obese are more likely to have low fitness levels and to have yo-yo dieted. They are more likely to be of lower socio-economic status and to have experienced weight-based discrimination. All of these factors are linked to poorer health. The vast majority of studies do not control for these variables, and when they do, the mortality relationship decreases or disappears completely (Bacon, 2011Lantz 2010). Therefore, any of these factors may actually be responsible for the slight increased risk of death seen in young people with BMIs over 35, rather than extra body fat.

Follow the money

So why do the media and health groups scare us into thinking extra body weight is a huge killer, if that’s not what the research really shows?  There are several possible reasons:

  1. The media likes exciting (and panic-inducing) headlines.
  2. The weight loss, fitness and beauty industries are big businesses with a lot of influence. Even well-meaning health professionals and researchers are often influenced without realizing it.
  3. Our society is stuck in the mindset that thin is good and fat is bad. It can be very hard to change society’s way of thinking. Consider how uproarious it once was for Galileo to suggest that the universe did not revolve around the Earth?  He was placed under house arrest and threatened with torture. Many people reject evidence that goes against what they believe to be facts.

Health at Every Size®

Regardless of your size, the best way to improve your health is with a Health at Every Size approach.  With this approach, you learn to care for your mind, body and soul without focusing on weight.

Learn more

If this is the first time you are hearing about this perspective, you may be skeptical.  I get it.  Take some time to review the supporting research.  I recommend any of these excellent resources:

  • HAES Curriculum Overview video
  • Review article Weight Science: Evaluating the Evidence for a Paradigm Shift by Linda Bacon, PhD and Lucy Aphramor, MS, PhD, RD
  • Katherine Flegal’s 2013 meta-analysis
  • Chapter 5 in Secrets from the Eating Lab by Tracy Mann, Ph.D.
  • Chapter 6 in Health at Every Size by Linda Bacon, Ph.D.
  • Chapters 2 and 8 in Beyond a Shadow of a Diet by Judith Matz and Ellen Frankel
  • Chapters 1 & 2 in The Obesity Myth by Paul Campos
  • Chapters 1 & 2 in Fat Politics: The Real Story Behind America’s Obesity Epidemic by J. Eric Oliver

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