1.  Everything in moderation. ("All foods fit" as part of a healthy diet.)
FALSE.
Particularly for people affected by obesity, there is little basis to argue that "foods" like soda (with artificial sweeteners or 100 percent empty calories) are "part of a healthy diet." One might be healthy in spite of consuming sodas and heavily processed foods, but certainly not because of their consumption, moderate or otherwise (Is there a credible argument that smoking is part of a healthy lifestyle if consumed in "moderation"?). Edible food-like substances, do not a healthy diet make, contrary to what Big Soda executives may claim. (To quote Upton Sinclair, "It is difficult to get a man to understand something when his salary depends upon his not understanding it.")

2.  A calorie, is a calorie, is a calorie.
FALSE.
The evidence is very, very clear: not all calories are created equal. Calories from sugar are far more damaging to health and metabolism than calories from, say, nuts. Functionally, the calories are simply not equivalent.

3.  3,500 calories equals one pound of body weight.
FALSE.
Another debunked myth that refuses to die, even within the medical community. This fallacy assumes that (a) people of the same height and weight have identical metabolisms, etc., and (b) to lose weight, this necessary deficit of 3,500 calories will stay the same or "static," over time as one loses weight. This is inaccurate, as one's energy needs are dynamic, always changing as the body adapts to declining weight. Newer, more sophisticated models can predict the effects of altered energy in/energy out concepts on weight over time with much greater accuracy. At least one such calculator is currently available online for public use, for free.

4.  To lose weight, just eat less and exercise more.
FALSE
. While this may seem true in theory, in practice, it's not nearly so straightforward. People affected by obesity may actually be exercising more and eating less. Woman A, who formerly weighed 200 pounds, but now weighs 150 pounds must eat significantly less to maintain this weight than does Woman B, who has consistently weighed 150 pounds. And Woman A may also expend significantly less energy during comparable physical activity and at rest than does Woman B. This inequity appears to hold true for Woman A, years after the weight loss, and quite possibly forever. In addition to these physiological changes, the "eat less, exercise more" tenet fails to consider other important factors that affect weight such as sleep. 

5.  People are overweight because they're gluttonous and lazy.
FALSE.
Classic studies on twins, adoption, and twins reared apart, show that weight is highly genetic, with heritability estimated to be as high as 70 percent (environmental influences on our genes, "epigenetics," notwithstanding). With rare exceptions, the strong genetic component of body weight has been largely ignored, perhaps, in part, because it's an inconvenient truth for both our $61 billion annual weight loss industry and our unflagging zeal for self-improvement.

Weight is almost as heritable as height, yet we hardly view someone's height as an indictment of her character or self-discipline. ("She has such a pretty face! If only she hadn't let herself go, she wouldn't be… so short.") Considering the strong genetic and biological forces that powerfully influence weight, the bias, stigma, and discrimination commonly associated with obesity warrant serious reflection.

Stacey C. Cahn, PhD is Associate Professor of clinical psychology at the Philadelphia College of Osteopathic Medicine. She specializes in obesity, eating disorders, body image and cognitive-behavioral therapy.

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