From Our 2008 Archives

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

By Miranda Hitti
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.

Myth: To eat less sodium, avoid salty-tasting foods and use sea salt in place of table salt.

Reality: Your sense of taste doesn't always notice sodium, and sea salt or other gourmet salts aren't healthier than table salt.

"Just because it doesn't taste salty doesn't mean that it isn't salty," Rosenbloom says. She says many processed foods contain a lot of sodium -- check the label.

Sea salt, Rosenbloom says, contains slightly less sodium per teaspoon than table salt only because sea salt is coarser, so fewer grains fit into the teaspoon.

Myth: Drinking more water daily will help you lose weight.

Reality: There's no evidence that water peels off pounds.

Foods containing water -- such as soup -- can fill you up, "but just drinking water alone doesn't have the same impact," Rosenbloom says. "Our thirst mechanism and our hunger mechanism are two different things."

Myth: Whole grains are always healthier than refined grains.

Reality: Whole grains are a healthy choice, but you needn't ditch refined grains. "You can have some of each," Rosenbloom says.

The U.S. Department of Agriculture's "My Pyramid" dietary guidelines recommend getting at least half of your grain servings from whole grains.

"It doesn't say you have to replace all of your breads with whole grains or all of your foods with whole grains," Rosenbloom says. She adds that enriched grains -- refined grains with certain nutrients added (such as wheat enriched with folic acid, an important nutrient for preventing neural tube birth defects) -- have some perks.

"Enriched grains generally are going to have more folate, thiamin, riboflavin, niacin, and iron. The whole grains usually have more fiber, vitamin e, selenium, zinc, potassium -- so there's kind of a trade-off," Rosenbloom says.

Myth: Sugar causes behavioral problems in kids.

Reality: You might want to check your expectations about sugar and children's behavior.

For most children, "the excitement that kids have when supposedly they eat sugar is probably more related to the event and the excitement of the event than it is to actually consuming sugar," Rosenbloom says.

She cites research showing that when parents think their kids have been given sugar, they rate the children's behavior as more hyperactive -- even when no sugar is eaten.

Myth: Protein is the most important nutrient for athletes.

Reality: "It is true that athletes need more protein than sedentary people. They just don't need as much as they think. And they probably don't need it from supplements; they're probably getting plenty in their food," Rosenbloom says.

But timing matters. Rosenbloom recommends that after weight training, athletes consume a little bit of protein -- about 8 grams, the amount in a small carton of low-fat chocolate milk -- to help their muscles rebuild.

"That's probably all you need," she says. "You don't need four scoops of whey powder to get that amount of protein."

How to Spot a Diet Myth

New diet myths can crop up at any time; fads come and go. To Duyff, the task of telling nutrition myth from reality boils down to this: Step back, check out the evidence, and be a bit skeptical. Here is Duyff's specific advice:

  • Look for red flags, such as promises that sound too good to be true or dramatic statements refuted by reputable health organizations.
  • Think critically. Consider the "facts" touted in diet myths. Are they from biased or preliminary research? "One study doesn't make a fact," Duyff says. "The messages need to be evidence-based," which means multiple studies conducted in large groups of people and reviewed by independent scientists.
  • Ask an expert. A registered dietitian or other health professional can help you tell nutritional fact from fiction.
  • Remember, there are no magic bullets. "The true approach to good health includes an overall healthy eating pattern, enjoyed and followed over time," Duyff says.

SOURCES: Christine Rosenbloom, PhD, RD, CSSD, professor, division of nutrition; associate dean for academics, Georgia State University, Atlanta. Roberta Duyff, MS, RD, FADA, CFCS, author, American Dietetic Association Complete Food and Nutrition Guide. U.S. Department of Agriculture: "How many grain foods are needed daily?"

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