Obesity Myths You Probably Believe

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5 Myths About Obesity

Given how much time and money so many of us spend on trying to lose weight, it's shocking how much false information exists about the topics of obesity and weight loss. A recent study in the New England Journal of Medicine described several pervasive obesity myths in an attempt to end these misconceptions and set the record straight. Check out our slideshow to find out how many of these obesity myths you might still believe.

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Myth: If you make small changes in what you eat or your physical activity, you'll lose a lot of weight—and keep it off.

Truth: This erroneous obesity myth is based on one of the first things you'll hear in a college nutrition class: the 3,500-calorie rule. This rule states that if you cut out 3,500 calories from your diet, you’ll lose one pound, and if you eat an extra 3,500 calories (beyond what you burn), you’ll gain one pound. The problem is that the rule is based on short-term experiments in men on very low-calorie-diets. In real life, it just doesn't work that way. You don't keep losing weight at the same rate over time, because, as weight is lost, the energy your body needs changes.

"The one myth [that hurts perhaps people the most is] the 3,500 calorie rule," Krista Casazza, a co-author of the New England Journal of Medicine paper and an assistant professor in the department of nutritional sciences, University of Alabama, told TakePart. "It can, in some instances, make or break a weight loss effort at the individual level...We're told that if you cut your calories by 3,500 you'll lose a pound. But that assumes everything stays exactly the same.” But, she says, the body adapts to any change, including weight loss, making sustained weight loss not such an easy equation.

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Myth: Physical education (PE) classes play an important role in preventing or reducing childhood obesity.

Truth: Oh, if only this were true. With one-third of the nation's children obese or overweight, many school districts are implementing more PE classes. But PE classes, as they are designed today, don't always lower the body mass index (BMI) of kids as we might hope.

Consider a school district or a superintendent who is worried about obesity in kids and wants to help. "They have one shot at doing something and they act on misinformation," Casazza says. "They may choose to do something that's ineffective. PE, as currently delivered, doesn't curb the obesity epidemic. So they are left with wasted resources." What is more effective? Programs that involve parents and kid getting support for weight loss at home seem to work better.

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Myth: Breastfeeding helps protect kids against obesity.

Truth: Breastfeeding advocates are fiercely protective of their cause. And rightly so. Nursing has many advantages for babies, including increased protection against some types of illness. However, the idea that breastfeeding can reduce the risk of obesity later in life is flat-out unsubstantiated. But even the World Health Organization promotes this obesity myth.

"We've published on that [myth] before, and we continue to get grilled about it," Casazza says. "I think that people just really want to believe that. It's probably the hardest one to debunk. There is no evidence that suggests breastfeeding is going to prevent obesity. Breastfeeding has numerous health benefits. It's just that obesity prevention isn't one of them."

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Myth: If you want to lose weight and keep it off, it's better to do it slowly and gradually, not lose a lot of weight quickly.

Truth: You've heard it before: "Don't try to lose weight fast; you'll gain it all back." Or: "Lose weight in a healthy manner—about one or two pounds a week—in order to maintain a long-term weight loss." This may be one obesity myth that people will be happy to learn is false: Go ahead and lose weight fast; it makes no difference. Studies show that rapid weight loss achieved on very low-calorie diets produced about the same weight loss in the long-term as slower weight loss. In fact, the authors wrote: "...a recommendation to lose weight more slowly might interfere with the ultimate success of weight-loss efforts."

The fact is, weight loss is complicated and there are few easy, rock-solid recommendations, Casazza says. "Because it's complicated, we have a responsibility to ask questions. It means we need to provide the strongest evidence for our recommendations."

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Myth: Having sex burns 100 to 300 calories for each participant.

Truth: Another obesity myth we sure wish were true. But, sorry, it’s wrong. This myth is based on a model of sexual activity featuring a 154-pound man and the time spent having sex. It doesn't take a math genius to see where this is headed: People of different weights burn calories at different rates. Moreover, the myth of 100 to 300 calories burned is based on roughly an hour of lovemaking. The average bout of sexual activity is six minutes, the authors note. The 154-pound man would likely burn about 21 calories during sex—slightly more than watching television for the same amount of time.

"The sex myth is on hundreds of websites," Casazza says. "Nobody stops to say: 'How could they know that? How could they test that? Who would volunteer for that study?' "