This advice from CrossFit that may sound reasonable: “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.” This strict Paleo or zone diet comes straight from official CrossFit nutritional advice. CrossFit says that eating Paleo will burn fat, increase muscle gains and aid you in recovering from CrossFit workouts of the day. But here’s the catch: No significant scientific evidence supports the CrossFit trainers who say ketogenic or other low-carb diets enhance performance.

That’s the word from Ball State nutrition and dietetics professor Carol Friesen. She is co-author of a new study published in the journal Sports. Friesen says dietetic professionals describe the Paleo diet as “debatable” at best.

The problem is that most CrossFit trainers get their diet information from other CrossFitters or from the Internet. The majority of almost 300 trainers surveyed for the study said they have no formal nutritional training.  It’s only at levels three and four of certification that CrossFit professionally addresses nutrition. That means trainers who haven’t reached higher levels of CrossFit instruction are doling out advice from dubious sources, said Friesen.

“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.

The Paleo way of cutting carbs while working out hard can make workouts feel more difficult and recovery tougher. Active women may find the opposite of CrossFit advice works for them. Eating carbs during or after workouts can offer many benefits such as a stronger immune system.

It’s not just CrossFit personal trainers who may lack formal nutritional training. The issue may come up with all types of gym trainers. Get your nutritional advice from qualified, degreed professionals. Research your own needs and pay attention to what your body tells you about different ways of eating.

Read More: Why You Probably Shouldn’t Take Diet Advice from Your CrossFit Coach