As a fitness professional with a background in therapy, I've found that its important to question the assumptions we make about weight and health. As part of this process, I am currently reading Body of Truth by Harriet Brown.
What I would like to share now is four important lies Brown addresses in her book. For more detail on these lies and the research both showing how the lies happened and what the truth is, go read her excellent book.
1. The Lie: Americans are getting fatter and fatter- at this rate nearly half of us will be obese by 2030!
The Truth: American rates of obesity and overweight actually leveled off around 2000. Most important to remember is that there is no defining explanation for why our weights have been increasing. Many experts like to point to eating too much, or the wrong kinds of things, or too little exercising as the culprits. But in reality there are other factors that have been shown to be connected to weight increases: poverty, chemical contaminants like PCBs and pesticides, drugs that treat nearly any kind of mental health condition, and the low-fat craze of the 1980s.
2. The Lie: Obesity can take a decade or more off your life
The Truth: There is no linear relationship between a person's BMI and life expectancy. In fact, its more of a U curve (and a very gently sloped U at that) where those with the lowest risk for early death are in fact slightly overweight. Those considered mildly obese have the same risk of dying early as those in the normal category. Check out this Nature article that draws primarily on Katherine Flegal's excellent well replicated studies on this topic.
Three key things to remember here:
1.Only severe obesity correlates with a shorter life span.
2. Being overweight correlates with a longer life span
3. The effects of obesity on morality predictions are low overall
4. All of these relationships are merely correlations, not causations. There is no established cause and effect between weight and mortality.
3. The Lie: Being fat causes heart disease heart disease, stroke, type 2 diabetes, and other serious illnesses
The Truth: There are demonstrated correlations but not causations between obesity and health conditions like heart disease, type 2 diabetes, gallbladder disease, stroke, fatty liver disease and risk factors for those diseases. Type 2 diabetes has the strongest correlation, particularly for those under 55 with BMIs over 40. The lack of demonstrable causation here is very important to keep in mind. Researchers like Robert Lustig has discovered that we are not even sure if weight gain or insulin resistance (the illness of diabetes) comes first.
We also have very little research that takes into consideration how physical activity impacts all of this. However, researchers like Steven Blair and Paul McAuley argue that its healthier to be fit and fat than unfit and thin, citing research showing that being physically unfit is as much or more of a risk factor for heart disease and death as weight-related risk factors are. What's more, study after study has shown that overweight and moderately obese patients with some ailments actually live longer than normal-weight patients with the same problems.
4. The Lie: Dieting makes us thinner and healthier
The Truth: Studies show that nearly everyone who diets winds up heavier in the long run. Many people's health suffers rather than improves. And repeated dieting can cause a whole series of psychological and physical issues. Dieting is even a major risk factor for binge eating and obesity.
I am not posting these to say I know any solution or "correct response" to any of these lies. However, I think its crucial for us to take a look at the myths of health and weight around us with a critical and aware eye. I'll talk more about exercise, weight, and health in future articles. But for now I will leave you with this video:
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