The Truth About Diet Urban Legends

Experts set the record straight on some of the top weight-loss myths of the last 30 years

Full disclosure: I have experimented with most (though not all) of these popular weight-loss methods: from an all tuna plan in 7th (!) grade to the college era diet that allowed me to consume as many Snackwell cookies and Heinekens as my heart desired. Then there was the “caveman” diet I tried with my husband, a fan of the workout that espouses it. This left me craving white carbs so desperately I was ready to stuff a bagel into a baguette and call it a bagel/baguette sandwich. And eat it.

And yes, many of these diets worked (not counting the beer and cookies)… at first. The reason, say experts, is that any time you drastically change your eating habits—in any way—you're going to see results on the scale. The problem is sustainability. “If you can't envision sticking with a diet for the rest of your life, then it's not a good eating plan,” says Janet Brill, R.D., Ph.D., a consultant in private practice and author of Cholesterol Down. We asked Brill and Nicolette Pace, R.D., CDE, about nine of the most popular dieting myths of the last 30 years—and why they're more hype than help.

Blood type card
1. You Should Eat by Your Blood Type

Whether you're A, B, A/B, or O, the theory goes that depending on your blood type, you should adhere to one of four possible eating plans: low carb/high protein, low fat, vegetarian, or just an overall balanced diet. The reasoning is based on biochemistry and evolutionary theory and, according to both Pace and Brill, has no scientific proof whatsoever.

“Blood type has to do with receptors on red blood cells and doesn't dictate what you should or shouldn't eat,” Brill says. If you match your diet to one of the blood type plans and lose weight, the reason is because of a sudden change to your diet or drop in calories, not because you're a universal donor.

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