Inti St. Clair  /  Getty Images File
Personal trainers can show you how to pump iron, but think twice about following their diet plans, experts say.
By MSNBC contributor
updated 9/20/2005 1:52:33 PM ET 2005-09-20T17:52:33

Should you trust dietary advice from a personal trainer? Can abdominal crunches give you a belly bulge? Smart Fitness answers your queries. Have an exercise question? To send us an e-mail, click here . We’ll post select answers in future columns.

Q: To help me lose body fat my trainer advised me to eat a high-protein diet five days a week and a high-carb diet on Wednesdays and Saturdays. Is this a realistic approach? I'm a little skeptical.

A: As you should be. Experts consulted for this article aren't aware of any evidence supporting this diet as a magical formula for weight loss.

Cynthia Sass, a registered dietitian and personal trainer in Tampa, Fla., says it's a common myth that high-protein diets help people burn the most fat when they exercise.

Actually, she says, people who don't eat enough carbs could even end up defeating their fitness goals by burning muscle during aerobic activity because their bodies don't have enough of their preferred fuel source — carbs.

"It's impossible just to burn pure body fat," she says.

Sass says she also doesn't know what possible benefit would come from carbo-loading on Wednesdays and Saturdays.

When it comes to weight loss, calories are what matter most. "Losing body fat percentage is a function of burning more calories than you eat but still consuming enough calories to support your body," says Sass, a spokesperson for the American Dietetic Association.

It's important not to consume too few calories, she explains, because this sends your body into survival mode, prompting it to hang on to fat stores.

Sass recommends making an appointment with a registered dietitian, at least for an initial consultation to get your nutrition plan on the right track.

Most personal trainers simply haven't undergone enough nutrition education to prescribe diet plans, she notes, and in 29 states and Washington, D.C., it's actually illegal for them to do so unless they're also licensed as a registered dietitian.

  1. Don't miss these Health stories
    1. Splash News
      More women opting for preventive mastectomy - but should they be?

      Rates of women who are opting for preventive mastectomies, such as Angeline Jolie, have increased by an estimated 50 percent in recent years, experts say. But many doctors are puzzled because the operation doesn't carry a 100 percent guarantee, it's major surgery -- and women have other options, from a once-a-day pill to careful monitoring.

    2. Larry Page's damaged vocal cords: Treatment comes with trade-offs
    3. Report questioning salt guidelines riles heart experts
    4. CDC: 2012 was deadliest year for West Nile in US
    5. What stresses moms most? Themselves, survey says

Walt Thompson, a professor of kinesiology and health at Georgia State University in Atlanta and a spokesperson for the American College of Sports Medicine (ACSM), points out that requirements for personal training certifications vary widely, with some programs requiring extensive training and others a weekend course.

"Basically anybody can call themselves a personal trainer," he says.

The ACSM has one of the most rigorous certification programs, but the group still says its trainers should discuss no more than the most basic nutrition guidelines found on the government's food pyramid.

Many trainers, however, go too far by doling out bad nutrition advice, according to Thompson. "It's incredible how widespread it is," he says.

And though many gyms have personal trainers selling supplements, they shouldn't, says Nancy Clark, a sports nutritionist at Healthworks, a fitness center in Boston.

"It's a huge business," she says, but one that concerns her because supplements are not well-regulated and some of them could be harmful. Some herbs, for instance, can damage the liver and others may be contaminated with lead or other toxic substances.

Q: I have a flabby stomach. Is it true that doing crunches will make it bigger due to muscle build-up? How do I get rid of the fat on my stomach and work toward making it flat?

A: If you're worried that working your abs will make them bulk up the way biceps do, don't fret. It won't happen.

Quite the opposite. Doing crunches and other abdominal exercises actually tightens your mid-section, helping to make it appear smaller and more toned.

But you won't get that coveted "six-pack" look if you've got a lot of fat on top of or below your abs.

To reduce the fat, you must lose weight through diet, physical activity or, preferably, both. Keep in mind that there's no way to lose the weight in just your abs. That notion is called spot reduction, and it doesn't work.

But a combination of aerobic activity and abdominal exercises can help whittle your middle.

Smart Fitness now appears every other Tuesday.

© 2013 msnbc.com

Discuss:

Discussion comments

,

Most active discussions

  1. votes comments
  2. votes comments
  3. votes comments
  4. votes comments