Walk into any CrossFit box and you can expect to have most of what you thought you "knew" about health and fitness challenged. This cutting-edge, outsider vibe is a big part of the appeal to many people, especially those tired of doing the same old thing and not seeing results. But it's not just your squat form that will get overhauled (no butt winks allowed!): You'll likely get advice about changing your diet, too.
CrossFit and the Paleo diet go together like peanut butter and jelly—you rarely get one without the other, and together they're said to make something better than either alone. (Although this analogy only goes so far, as neither peanut butter nor jelly are considered kosher under most Paleo diets.) Proponents say that eating like our Paleolithic ancestors will increase muscle gains, torch fat, and aid in recovery from the hardcore old-school WODs, or workouts of the day, that characterize CrossFit. Trainers often coach their clients to stick to a strict Paleo or zone diet, as epitomized by the official CrossFit nutritional advice: "Eat meat and vegetables, nuts and seeds, some fruit, little starch, and no sugar. Keep intake to levels that will support exercise but not body fat." (PS: Did you know the original Paleo diet included cannibalism?)
While that advice may sound reasonable, there's actually no significant scientific evidence that shows Paleo, ketogenic, or other low-carb diets are as effective in enhancing performance as many CrossFit trainers profess, explains Carol Friesen, a nutrition and dietetics professor at Ball State and co-author of a new study published in the journal Sports.
"The CrossFit training emphasizes use of the Paleolithic diet, a diet described by dietetic professionals as 'debatable' at best," Friesen says in a press release.
In fact, cutting carbs while working out hard can have the opposite effect, making workouts feel tougher and recovery slower, especially in women, says Sharon Richter, a registered dietitian. For active women, eating carbs during or after workouts can offer many benefits, including a boosted immune system.
Now, this doesn't mean that all CrossFit trainers are all bad—plenty are highly educated and provide good information. Rather, it's that most CrossFit trainers don't have formal nutritional training. Of the nearly 300 trainers surveyed for the study, the majority reported that they get their diet information from other CrossFitters or from the internet. Plus, nutrition isn't even addressed professionally until levels three and four of the CrossFit certification, which leaves a lot of trainers giving out advice from dubious sources, says Friesen. (Here are more reasons why personal trainers shouldn't always dole out nutrition advice.)
"People spend a great deal of money each month to be trained by 'professional trainers' and should expect solid advice—not something you can find online," she says. "When you walk into a box, a person should expect a solid experience that meets all their needs. If the trainers can't give you solid advice on nutrition, why would you expect anything else to be correct?"
This issue isn't unique to CrossFit, of course. Personal trainers of all types often don't have nutrition degrees and may rely on outdated or inaccurate sources. Even in nationally recognized programs, like the Certified Strength and Conditioning Specialist certification, just a quarter of the information and the exam is devoted to nutrition—and even that material stays at a fairly basic level.
Bottom line? Don't expect fitness experts to automatically be nutrition experts, too. Take gym nutrition advice with a grain of salt, do your own research, pay attention to how your body reacts to different ways of eating and, if you need more information, seek out a qualified professional.