What is a fad diet?

Michigan State University food science and human nutrition assistant professor Robin Tucker explains popular diets— and if they’re worth trying.

Diets are a lot like fashion: they offer the promise of an improved appearance, and both can go in and out of style.

In the 1980s, low-fat diets received the most attention. In the ‘90s and early 2000s, low-carb, high-protein diets, such as South Beach and Atkins, took over. Today, “clean” and “natural” diets, like the Whole30 and paleo, lead the fad diet pack. The ketogenic (keto) and FODMAP diets are also popular.

“I think what most people think that comes to mind as a fad diet is maybe something that is being touted as a quick fix, you’ll lose 10 pounds in a week kind of thing, where there’s not a lot of evidence to support it,” said Robin Tucker, Michigan State University (MSU) assistant professor of food science and human nutrition.

Popular fad diets: An overview

The Whole30 and paleo diets are both elimination diets focused on weight loss.

The Whole30’s main goal is to reset your digestive system by avoiding processed food. On the Whole30 diet, you can’t consume alcohol, sugar, grains, legumes or dairy for 30 days.

The paleo diet supposedly mimics the way our ancestors ate, “but no one really knows [how they ate] to any real level of certainty,” according to Tucker. No dairy products, legumes and grains, potatoes are allowed on the paleo diet.

Originally developed to treat epilepsy in children, the keto diet involves drastically reducing carbohydrate intake (less than 50 grams per day) and eating healthy fats with a moderate amount of protein.

“By nearly eliminating carbs, the body switches fuels, starts burning fat and producing ketone bodies (a process called ketosis), which the brain can use,” said Tucker. “Fat intake increases on the diet, so there’s no real net loss of body fat.”

The FODMAP diet is intended for people with irritable bowel syndrome (IBS) and also involves elimination of certain foods, but is not intended for weight loss. FODMAP stands for Fermentable Oligo-, Di-, Mono-saccharides and Polyols. These are short-chain carbohydrates people with IBS have trouble digesting.

“The goal is to avoid eating foods high in those compounds that trigger symptoms,” said Tucker, who noted there’s growing evidence to back the effectiveness of the FODMAP diet. “You start by eliminating specific foods and then gradually reintroduce to see which trigger symptoms.”

There are people who don’t have IBS and try the FODMAP diet, which presents a concern, said Tucker. The same goes for those who adopt a gluten-free diet, but don’t have Celiac disease, or a gluten intolerance or allergy.

“Whenever you arbitrarily exclude a food group, you’re going to be missing some of those nutrients, and that’s what dietitians start to worry about,” said Tucker. “It’s not that you can’t get those nutrients from other stuff, but you just have to be a little more careful about what you’re eating.”

So you want to try a fad diet?

It’s understandable to want to dive right in to something that promises a quick, easy solution and is getting a lot of buzz, but Tucker advised those considering a fad diet to do their homework.

“If you’re thinking about a fad diet, I would do some research about the elimination part,” she said. “What are you eliminating, and what might that do to you overall, health-wise?”

Tucker emphasized talking to people who have advanced training in nutrition, such as dietitians and researchers on the subject. In addition to in-person, she indicated the internet as an effective way to reach out to reliable individuals who can help.

“Make smart choices,” Tucker said. “If you aren’t sure if it’s smart, consult somebody. How do you do that? Many dietitians have blogs. Send a message to that dietitian and ask them to cover that subject on their blog or on their podcast. Interact with professionals who can help you make informed decisions.”

Trusted professionals can give all of the research-backed information they know to someone who might be interested in a fad diet — their job is to share the information they know. Tucker recognizes that not everyone will listen: people are often swayed by anecdotal evidence, and the decision ultimately rests with the individual who is considering the diet.

“Even if I’ve told you I don’t recommend [a diet], it’s still your right and your privilege to say ‘forget what she said. I don’t care. I’m going to do it and see what happens.’” Tucker said. “I just want to make sure that you have all of the information to make that decision, then you’re on your own after that.”

Tucker also noted the importance of finding the best diet for you —the one you can stick to.

“I love carbohydrates. Going on the ketogenic diet is going to make me crazy,” she said. “I’m not going to able to stick to it. So why would I even put myself through that? But I know that about me. If you’re somebody who could take or leave carbohydrates, but really like more savory kinds of foods and things like that, then maybe that diet will be easier for you to stick to.”

An easy-to-maintain choice might not always involve going on a fad diet. According to Tucker, it could be as simple as swapping out a high-calorie yogurt for a low-calorie one if you know giving up dairy would be difficult for you.

“Do some online research,” said Tucker. “Figure out how many calories are in whatever you’re interested in, and can you make better choices. I’m more about better choices than excluding or not doing things, and I think that is ultimately more sustainable down the line.”

Our Table host Sheril Kirshenbaum interviewed Tucker about low-carb diets for an episode of WKAR’s “Serving Up Science” in August 2018. Listen to it here

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