Nutritionist. Food Coach. How Good Is Their Diet Advice?

Anyone can claim to be a "nutritionist" or "food coach." So here's what you should look for.

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If you feel the need for professional help with your eating habits or diet, you may assume a nutritionist is the person to talk to. As it turns out, that's not a particularly specific or useful term—a point driven home by recent advice published in a magazine from a "nutritionist" who claimed weight loss is aided by eating carbs and protein at separate meals, a notion not supported by science. (Mariah Carey followed similar advice from her trainer/nutritionist in 2008.)

By no means is everyone calling herself a nutritionist (or a nutritional consultant, food coach, or weight-loss specialist) dispensing hogwash. But for consumers attempting to make an informed choice, the titles are meaningless; they don't capture the possessor's education, experience, or credentials. And those are all important when it comes to seeking eating advice, given the proliferation of fad diets and quick weight-loss schemes. “I can’t think of a field that has more quackery than nutrition,” says Lisa Sasson, a clinical associate professor of nutrition and food studies at New York University.

[Even though the big eating holidays are behind us, read 6 Stupid Holiday Diet Tips You Should Ignore—and 1 You Shouldn't for guidance that makes sense year-round.]

One specific title to look for: registered dietitian. In order to call himself an R.D., a person must have an undergraduate degree in nutrition or dietetics—or the equivalent in coursework—from an accredited institution, says Dee Sandquist, an R.D. and spokesperson for the American Dietetic Association, the professional organization that credentials R.D.'s (through the Commission on Dietetic Registration). On top of that, R.D.'s have to complete a yearlong, supervised internship and pass a national exam. And they must get credits in continuing education on an ongoing basis. Anyone calling herself simply a dietitian is also legally supposed to be an R.D.

The American College of Nutrition also issues C.N.S. (certified nutrition specialist) credentials for people with advanced degrees—master's, doctorate, M.D.—in nutrition or related areas. They, too, have to sit for an exam and also earn continuing education credits, says Madelyn Fernstrom, director of the nutrition and weight management program at the University of Pittsburgh Medical Center and author of The Real You Diet. Either an R.D. or C.N.S. designation means the holder has relevant education and experience, has passed an exam, and will make evidence-based recommendations, says Fernstrom.

I saw Fernstrom identified as a "board-certified nutritionist," referring to her C.N.S. certification. (She has a Ph.D. from MIT.) But the term "nutritionist" alone is meaningless. "It's not a bad thing," says Fernstrom. "But it's like saying you're a cook—you could be working in Denny's or at a five-star restaurant." So ask: What's the nutritionist's educational background? Does she have an R.D. or a C.N.S.? What experience does she have? Has she treated patients like you before? Is her practice grounded in scientific evidence? "You don't have to discount someone who has some other certification, but do your homework," Fernstrom says. "It's just like reading labels."

Making matters even more confusing is that most states have some kind of licensing, registration, or certification system in place but the systems vary in rigor. Some won't allow anyone to practice without meeting certain requirements, others allow qualified persons to use the titles "dietitian" or "nutritionist" but let others practice under different job titles, and others simply require people, regardless of credentials, to register with the state. (Here are the laws, state by state.) To be certain you're getting someone who has met national industry standards, look for an R.D. or C.N.S. credential.

If you have specific needs—say, you're an athlete who wants to know how to recover from races, are a newly diagnosed diabetic seeking help in planning meals, or are seeking help for your overweight child—be even more pointed in your questioning. Ask what specialized education or experience the person has. The ADA, for example, has additional credentials for R.D.'s who want to focus on kidney disease or cancer patients, children, the elderly, or athletes. The "Ask the Dietitian" website, run by Joanne Larsen, a registered dietitian, has some additional tips for vetting anyone offering nutrition advice. Among them: Question eating plans that require the purchase of certain supplements, avoid diets that eliminate entire food groups or prescribe "magic" foods that must be eaten daily, and ask for research—not testimonials—to substantiate claims.

Correction: An earlier version of this article misstated Lisa Sasson’s title. She is clinical associate professor of nutrition and food studies at New York University.