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The Truth Behind 10 Diet Myths

Does Eating at Night Make You Fat? Is Caffeine Bad for You? Get the Facts on These and Other Diet Myths
WebMD Health News
Reviewed by Louise Chang, MD

Oct. 28, 2008 -- True or false: You'll get fat if you eat at night, high fructose corn syrup makes you gain weight, and caffeine is bad for you.

Those are all diet myths that got busted today in Chicago at the American Dietetic Association's annual meeting.

Meet the diet myth busters:

  • Christine Rosenbloom, PhD, RD, CSSD, of Georgia State University in Atlanta
  • Roberta Duyff, MS, RD, FADA, CFCS, the St. Louis-based author of the American Dietetic Association Complete Food and Nutrition Guide.

Here are 10 diet myths Rosenbloom shattered at the conference, and Duyff's tips on telling diet fact from diet fiction.

Myth: Eating at night makes you fat.

Reality: Calories count, whenever you eat them.

There's no proof for this myth, Rosenbloom says. She notes some small studies with mixed results, tests on animals, and a belief that because eating breakfast is linked to lower BMI, eating at night isn't as good. But all in all, Rosenbloom says, it's your calorie total that matters, day or night.

Myth: Avoid foods with a high glycemic index.

Reality: You could use the glycemic index to adjust your food choices, but don't make it your sole strategy for losing weight or controlling blood sugar, Rosenbloom says.

"For those people that are already counting carbs, this can be a way for them to fine-tune their food choices, but it isn't the be-all, end-all for weight loss," she says.

Myth: High fructose corn syrup causes weight gain.

Reality: "There's probably nothing particularly evil about high fructose corn syrup, compared to regular old sugar," Rosenbloom says.

She explains that this diet myth arose in 2003, when researchers noticed that obesity was rising along with the use of high fructose corn syrup. "They speculated that ... maybe we handle [high fructose corn syrup] differently than we do sugar," but "there really isn't any evidence to support that," she says.

The American Medical Association recently concluded that high fructose corn syrup doesn't contribute to obesity beyond its calories.

Myth: Caffeine is unhealthy.

Reality: Rosenbloom says there is some evidence that caffeine may have a positive effect on some diseases, including gout and Parkinson's disease, besides caffeine's famous alertness buzz.

Also, caffeine doesn't dehydrate people who consume it regularly, Rosenbloom says.

But she cautions that caffeine isn't always listed on product labels, and children who drink a lot of caffeinated energy drinks may get more caffeine than their parents expect. "Kids tend to guzzle these things, whereas an adult may sip a beverage," Rosenbloom says.

Myth: The less fat you eat, the better.

Reality: "For some people, counting fat grams can work for weight control, but it isn't the be-all end-all for people," Rosenbloom says.

She says that people with heart disease, diabetes, and metabolic syndrome may benefit from adding a little healthy fat -- the monounsaturated kind -- and cutting back on carbohydrates. But they shouldn't increase their overall fat intake -- just swap saturated fat for monounsaturated fat.

"If you go out to an Italian restaurant and you have triple cheese-meat-sausage lasagna but then you have a little olive oil on your bread, you're not doing much for your heart," Rosenbloom says.

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