This is an interesting piece, mostly for what the writer did not know or understand. Ms. Davies implies that working with “certified” professionals provides a level of assurance in terms of the usefulness of the advice that you might not have working with someone who isn’t certified. Bullshit. This is the same line of argument made by personal trainers in Washington, D.C., when they tried to get first-in-the-nation licensure requirements for personal trainers in their jurisdiction. They were crushed by opponents, led by the terrific Greg Glassman of CrossFit, who made a compelling argument that this was not but an attempt to limit access to the marketplace.

I would like to ask Ms. Davies and the assorted idiots quoted in this essay to produce evidence that working with a certified fitness or nutrition professional yields better health or performance outcomes than working with someone who does not have any certification. I am guessing that this clown car of American fitness doesn’t even know what evidence is.

Here is the most important way to learn about whether someone is a serious fitness or nutrition professsional: talk to them; talk to their clients and colleagues; LISTEN to what they say and observe HOW they teach. You’ll know credible and knowledgeable when you see it and hear it, and you’ll know a clueless, conflicted shill, too.

So while broad advice (for example, eat more whole foods) is likely fine, specific tips for preventing disease (eat “x, y, z” to manage your high blood pressure) are not, unless the information is given by a certified nutritionist. Those broad guidelines aren’t clearly regulated, however, giving personal trainers plenty of leeway in what they say.

“There are times it takes every single bone in my body not to blurt out, ‘That’s the dumbest advice I’ve ever heard,’ when I hear some of the nutrition tips given by exercise professionals,” says Lauren Slayton, registered dietitian and founder of Foodtrainers, a nutrition counseling center in Manhattan.

MarketWatch: Your personal trainer may not know what they’re talking about.