Become a Member

Get access to more than 30 brands, premium video, exclusive content, events, mapping, and more.

Already have an account? Sign In

Become a Member

Get access to more than 30 brands, premium video, exclusive content, events, mapping, and more.

Already have an account? Sign In



Why We Fall for Diet Fads

Exercise scientist Steve Magness on “bro science,” social media bubbles and how to avoid getting sold an agenda.

If you’re like most people, you’ve probably experienced the pressure of changing your eating habits due to a rise in new dieting trends. The ketogenic diet and meal-replacing shakes have made their way into your newsfeed. Claims such as putting butter in your coffee for more energy, drinking lemon juice with cayenne pepper to lose weight fast, eating exclusively meat to enhance health and performance, and many others, are no longer unusual.

These trends work because they take a bit of scientific evidence, such as the metabolic process of ketosis, shape an appealing narrative around it, and throw in a few claims such as losing weight or preventing cancer (complete with links to relevant studies, but lacking a complete picture). Once a diet trend catches on, all other diets that were encouraged before are rejected.

coffee with butter
photo: Shutterstock

In the 1990s, the low-fat diet became popular due to a widely accepted belief that consuming fatty foods would make you gain weight. Soon, everyone began eating less fat and more carbohydrates. Now, 20-plus years later, the narrative is reversed: Low carb, high-fat diets are believed to be the best way to lose weight.

How did we get to these conclusions? How are we still buying into trends that rise and fall in a few years, or even months, and lack credibility?

The Rise of Bro Science

Exercise Scientist and Coach at the University of Houston, Steve Magness, refers to this as “bro science,” or reasoning made by those who give out health advice but don’t have evidence to back up their claims. Rather than trying to dismantle each claim, Magness looks at the psychological phenomena that lead smart people to fall for diet trends.

“We only know our personal experience and don’t step back to look at other’s experiences,” says Magness, “We’re all familiar with the basics of how nutrition impacts our bodies and it’s simple to grasp onto. Because it’s so simple to grasp onto, we overestimate our knowledge. If we pick up a diet book, read a couple of articles, or listen to a podcast, all of a sudden our confidence on what we know about a diet is through the roof—but what we actually know is pretty minimal.”

He’s referring to what is knows as the Dunning Kruger Effect, a psychological phenomenon where someone who knows a little about a topic acts as an expert on it. This often happens on social media platforms where it’s easy for one person to reach many followers about weight loss methods. Meal-replacing shakes and vitamin cocktails are easily pushed online thanks to quick pitches that sound appealing and are easy to believe.

Bro Science Advisor
photo: Shutterstock

Take a juice cleanse, for example. A quick Google search reveals multiple testimonials of clearer skin, increased stamina, and better sleep. Cleanses are commonly advertised to flush out toxins and help you lose weight without describing exactly what toxins are being flushed from one’s body.

“If you asked what toxins they’re talking about, they wouldn’t be able to answer,” says Magness, “These stories function well in the social media world because it’s the quick-hit Twitter or Instagram post. Oh, toxins? Those are bad. But we aren’t doing a deep dive to see what that means or doesn’t mean. Social media allows us to get into our own little bubble. If we just follow the same kinds of people who are susceptible to these diet cleanses and keto diets, then it seems like everybody is doing it and it’s awesome. It becomes a reaffirming thing to be a part of this ‘group.’”

The ‘in vs. out group’ phenomena is common in the case of dieting because it’s a basic human instinct to determine who is with us and who is against us. You’ve probably noticed that if you question a diet trend, those who follow it are quick to get defensive. They’ll take the advice of someone selling them powder-based vitamin cocktails over that of a registered dietician.

Rather than taking professional advice from a qualified expert such as Magness, our instinct is to overestimate our own personal experience and assume it applies to everyone else. “We usually don’t step back and see that that person over there is completely different from me,” Magness says. “We had completely different upbringings in terms of dietary choices and physiology.

Magness says this individuality is why running is a great analogy for nutritional need. The training you need depends on your strengths and your background and your goals. “Nobody is going to say there is only one way to train for the Boston Marathon,” he says. “But that’s what we do with diet.”

Know Thyself and Keep it Simple

Magness believes runners have an advantage when it comes to determining if a diet trend will help or hinder training. Being a runner means enduring physical demands and stress that others don’t experience on a regular basis, therefore, making us more cautious about what we put in our bodies.

Of course, it goes without saying that no runner is going to have the perfect diet or always know exactly what their body needs, but it’s far easier to weed out what isn’t helping us because it’ll quickly show up in training when something feels off. For example, meal replacing shakes typically contain 200-400 calories each, and for someone in training mode, that’s more like a snack. Though it takes years of practice, tailoring one’s diet to meet the demands of your current training helps eliminate most fads that come and go over the years.

runner eating to match training
photo: Shutterstock

Magness’ advice to athletes? Keep it simple.

First, recognize when you’re being sold something. “Look for people and organizations that don’t have an agenda, aren’t selling a product and don’t have a bias,” Magness says. “A lot of misinformation that’s out there sounds good, but then you look at it and realize they’re selling a diet book or supplements. Stay away from that.”

Second, follow the lead of effective runners. “Look at what the best of the best runners are doing. While there’s a lot of variation in the specific details, very few of them are doing any fad diet to run fast. If 90% of the people running the fastest aren’t doing crazy stuff, chances are they aren’t the best for your health or performance,” Magness says.

And what are the best of the best doing? Look to Shalane Flanagan, elite marathoner, and co-author of the Run Fast Eat Slow cookbooks. Flanagan believes in eating her way to health through healthy fats and iron-rich foods.

Becky Wade Balanced Dinner
photo: Becky Wade

You can read food diaries such as the one 2:30-marathoner Becky Wade recorded for us during her training for this year’s Boston Marathon.

Or check out the balanced, endurance-adventure-fueling recipes of Morgan Sjogren, elite track athlete turned avid trail runner, in her recently-released book, Outlandish: Fuel Your Epic.