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Debunking Fad Diets with a Registered Dietitian

Fad diets are nothing new; they’ve existed since the days of Ancient Greece and are still thriving to this day. Today, diets like Weight Watchers, Whole30, cleanses, Keto, and Paleo are incredibly popular for weight loss— but are they actually effective? So many popular modern diets are one size fits all plans that promise the same radical weight loss for everyone across the board, but it’s not for the sake of their overall health. Instead, these fad diets focus on weight loss for the sake of being skinny. Before and after photos, special shakes, bars, and powders that promise to melt fat away, and the overall societal pressure to stay thin are still used to promote these potentially dangerous diets without any health warnings or proven research that they work. With so much misinformation, it’s no wonder that finding proper, safe, and healthy dieting advice today is like finding a needle in a haystack.

But it doesn’t need to be that way.

Kaitlyn Kennis MPH, RD, LD is a registered and licensed dietitian working in the Austin area. She studied Nutrition at the University of Texas at Austin and received her Masters of Public Health from UTHealth Houston in 2019. Previously, she worked at Houston Methodist Hospital with transplant patients, managing their diet plans to help them lose the weight needed to qualify for their life saving surgeries. Today, she works with cystic fibrosis patients across the Austin area, helping to prolong their lives with healthy eating and lifestyle changes. We sat down to discuss her thoughts on fad diets,  healthy diets, and how we as a culture got to this point.


How would you define a fad diet? 

It’s a diet that’s popular at the moment because it helps you lose weight quickly, but doesn’t really take into consideration your overall health.

Why don’t they work for a lot of people? 

Because they’re so restrictive. A lot of them cut out lots of different foods, usually foods that people really like, and it’s not sustainable over time to cut certain food groups out. Like the Whole30 diet cuts out all dairy and all grains. You do it for 30 days and then when the 30 days is over, you go back to the diet you had before and you gain all the weight back. And while that’s not good if your long term goals are to lose weight, it’s also not good for your heart to have that yo-yo effect of dramatic weight loss and gain.

Are there any particular groups of people that fad diets hurt the most?

I think people with actual Illnesses. Say someone tries a juice cleanse. That’s very hard to manage anyways. But if you have diabetes, it’s not great for you to be drinking juice every day because that’s going to make your blood sugar super high. You might lose some weight, but it’s not going to be good for your overall health. I think society makes weight loss as the overall goal and not really improving your health.

Do you have any opinion on which fad diets you dislike the most?

If you ask any dietitian, we’re all very anti-Keto diet. I remember when I was working with transplant patients I had a guy who needed to lose weight so he could donate his kidney to his wife. He did the Keto diet to lose weight and he did lose weight, so he met the BMI requirements for kidney donation. But it also caused him to have really high cholesterol, so he didn’t meet the criteria because his cholesterol was too high. He never had cholesterol issues before. But when you’re eating a diet that’s really high in fat, specifically high in saturated fat like butter and bacon, you’re going to have elevated cholesterol. So I think that people think, oh, you lose weight so you’re healthy and skinny. There’s a term for a skinny person that’s unhealthy, where their blood results are bad, but they’re skinny so everyone thinks they’re healthy. Then there’s people that are in a larger body and people think they’re unhealthy, but if you did all their lab results everything could come back perfectly normal. And so health is not just about appearance.

Why do you think they’re still so popular for so many people? 

If you just look back over time, you could ask our parents’ generation— they did Atkins and Slim Fast. There’s always going to be some diet that’s popular for people to lose weight, but they’re not sustainable because they’re so restrictive. People, especially Americans, want a quick fix. Doing a really restrictive diet will still take a while to lose weight, so you’ll get your results eventually, but you’re not going to do that diet forever because you’re going to be unhappy. For so many people, food is a part of their cultural diet and you know, brings happiness and good memories. If you have to cut those foods out it’s not a good way to live.

If you were trying to teach someone how to spot a not so good diet plan, what would you tell them to look for?

I think if it sounds too good to be true, it’s too good to be true. Like doing a juice cleanse to lose, I don’t even know what they claim, 20 pounds in a week or taking this special supplement to lose weight. If you’re choosing a diet for weight loss, it’s only going to work if it’s sustainable over time, it’s balanced, and everything can be allowed in moderation. But if there’s this diet that says you have to cut this entire food group out, it’s probably not good. There’s a difference in changing portion sizes or cutting back the amount of a certain food to help improve your health. But if it says there’s no bread allowed ever, that doesn’t make sense.

Are there any specific diet plans that you would recommend for a regular, healthy individual?

If you are someone who has no chronic illnesses or diseases, I recommend the Mediterranean Diet.

All of the information provided above is intended for educational purposes only, and this post should not be taken as medical advice. If you are seeking specified diet advice for your specific health needs, consult a registered dietitian.