When you're ready to lose some weight, navigating the universe of diet advice can be daunting. How do you separate fad from fact?

We took five top diet myths to a panel of dietitians to see which ones don't stand up to reality.

Fad Diets | Industry Secrets | Diet/Fitness

I have a slow metabolism, so I'll never lose weight.

"It's rare that someone has a slow metabolism and that's the only reason (they aren't losing weight)," said cardiac dietitian Toni Kuehneman, who helps patients organize their diets at Alegent Health Immanuel Hospital in Omaha, Neb.

In fact, while some beleaguered exercisers feel that people born with higher metabolisms have won the cosmic lottery, the fact is that heavier people tend to have higher metabolic rates, scientifically speaking.

"We find continuously ... that people with weight problems who have obesity have a higher basal metabolism compared to people who are lean," Dr. Jim Levine, an obesity researcher at the Mayo Clinic, told ABCNews. "Your basal metabolism is the calories you burn to keep your body going, so if your body is bigger, of course your basal metabolism is greater."

While you can expect your metabolism to slow by 1 to 2 percent for every decade after age 30, it is easy to combat that with increased activity. Kuehneman also suggested a technique she calls "intuitive eating," which calls for small meals every three to four hours.

Which brings us to Myth No. 2.

Skipping a meal is a good way to jump-start a weight-loss program

"Totally skipping a meal is a really bad idea," said Wild Oats nutritionist Gina Moss, a registered dietician and licensed medical nutritional therapist. "It causes your body to go into conservation mode."

Dietitians said evolution kicks in quickly when you starve yourself, even temporarily, transporting your body back to the time when man first stood upright.

"It sends a message to your body, 'Hey, I'm not getting sustenance. I'm not getting energy, so I better hang on (to calories) as fat,'" said Lisa Lewis, a trainer with ShapeXpress, an all-female gym franchise.

Fine. I'll eat. But only celery or cabbage soup or grapefruits.

The Internet has given new life to fad diets that promise rapid weight loss, and people on a deadline to lose weight before a big event often fall prey to their promises. Kuehneman said she's never read a single study that shows scientific benefits of such diets.

Still, the experts had to concede that the diets work for a while.

"You do drop weight," Lewis said. "It's not fat weight. It's generally water weight. When you return to regular eating patterns, the weight comes back."

"Everybody's looking for the quick fix," said Moss. "They do work, in the sense that if (cabbage soup is) all you're eating -- it's very low in fat, very low in calories and it fills you up. After a while you're going to get bored with that, and that's the biggest reason fad diets fail."

OK. I'm adding variety, but I'm avoiding high-fat foods like nuts and dairy.

Dietitians said they consider a study from the University of Tennessee's Dr. Michael Zemel to be groundbreaking proof that dairy actually helps weight loss. A blind study found that women getting calcium by drinking milk and eating cheese lost the most fat and maintained the most lean body tissue.

Kuehneman said the key to eating dairy is making the right choices. There are low- and no-fat yogurts, skim or 1 percent milk, and a new Robert's Dairy product called "Skim Extra." It is skim milk enhanced with seaweed fibers that delivers the same mouth feel as 2 percent. Kuehneman said she's a big fan.

As for nuts -- yes, they are high in calories and fat, but science shows it is the "good" fat. "Nuts contain the essential fatty acids, linoleic and linolenic acids, which are vital for growth, healthy skin and hair, blood pressure control, immune response and blood clotting," according to Yale-New Haven Hospital.

So enjoy them in moderation -- portions are key to all weight loss, dietitians said.

Oprah told me not to eat after 7:30 p.m.

The queen of talk makes a weekly mantra of her weight-loss policies, which include a strict 7:30 p.m. cutoff for all eating each day. But does the power of the advice match the power of Oprah Winfrey's voice?

Even her own trainer allows some wiggle room.

"That's what worked for her," said Bob Greene, Winfrey's personal trainer, answering a viewer's question on Oprah.com. "This is about managing your day."

Diet isn't a four-letter word.

Kuehneman, Moss and Lewis concurred, saying a cutoff time is a good approach to prevent late-night overeating. However, weight loss ultimately comes down to calories in and calories out, so you can eat any time of day as long as you don't exceed the number of calories you've burned that day. The key to debunking all diet myths, Kuehneman said, is to take apart the myth of diets themselves. She said the very nature of a diet suggests some kind of short-term fix for a problem that requires a long-term, permanent adjustment.

"Diet is a four-letter word. A diet usually won't be successful because (weight loss) has to be a lifestyle approach -- a wellness approach," Kuehneman said. "We are born knowing when we're full and knowing when we're hungry. That's what we need to get in touch with again."

Check back Nov. 21 to see if myths about the things you think you know about exercising are true.

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