Fad diets often cycle through pop culture, becoming popular for a few years, disappearing, then coming back “new and improved.” In the last few years, I’ve noticed low-carb diets making a comeback as well as gluten-free diets — without medical necessity — and, of course, Whole30 and paleo.

As a registered dietitian, I have many clients who come to me with questions about these fad diets. They want to know whether the diets work and if they can lose weight quickly and keep it off. I tackle these questions by presenting them with the diets’ pros and cons so they can make an educated decision about their nutrition.

Yes, sometimes these diets can help people in the short term or as a treatment for certain health conditions. But in my professional experience and personal opinion, these diets can do more harm than good overall.

To get a better understanding of why these types of diets don’t work, especially in the long term, I’ve provided an overview of four popular fad diets below.

It seems “gluten-free” is just about everywhere these days, from restaurant menus to whole aisles in supermarkets dedicated to gluten-free foods.

Going gluten-free means cutting out any foods that have gluten in them. That means eliminating breads, pastas, crackers, cereals, pizzas, and even beer. Doctors often prescribe this diet to people who have celiac disease.

Holly Strawbridge, former editor for Harvard Health, explains this diet’s rise to fame in recent years is “based on little to no evidence.” Instead, she pinpoints its spike in popularity as the result of testimonials from people who claim this fad diet promises weight loss and a boost in energy.

For those who don’t have a gluten-intolerance or sensitivity, this diet falls short in many ways.

First and foremost, it can potentially cause nutrient deficiencies, as it requires cutting out all:

  • breads
  • cereals
  • grains
  • pastas

These foods are often fortified with vitamins and minerals, meaning you could be missing out on iron and B complex (think thiamine, riboflavin, niacin, and folate), both of which are essential for health. This diet may also lack fiber, a major part of whole grains like breads, cereals, and pastas.

Gluten-free foods are also heavily processed and often rely on starch products like potatoes and rice. These don’t always provide the vitamins and minerals other grains have.

Finally, gluten-free foods can be super expensive, so if you don’t need to eat gluten-free, you’re shelling out more money for less nutrients.

Bottom line: Unless you have a gluten intolerance or sensitivity, there’s little to no benefits of going gluten-free.

Instead, opt for freshly made foods, like breads, for both their flavor and high nutritional levels.

The Whole30 diet has risen to fame in the last few years with promises of everything from curing digestive sensitivities to eliminating sugar cravings.

Whole30 requires you to cut out sugar, grains, dairy, legumes, and alcohol for 30 days. You then reintroduce each food group one by one and notice which, if any, cause a reaction.

While food allergies are on the rise, it’s important to remember that only an estimated 10 percent of American adults actually have food allergies.

Whole30 also focuses on eating whole, nonprocessed foods. While this isn’t inherently bad, and can definitely kick-start some healthy eating habits, it does mean cooking everything from scratch. This can be both costly and time-consuming, which isn’t achievable for everyone. Even minor things like small amounts of creamer or sugar in coffee are entirely off-limits.

There’s also the issue of how isolating this diet can be. Eating at restaurants or other people’s homes becomes difficult while following this regimen. So, if you’re looking to go out with friends for dinner or attend a dinner party, your choices could be vastly limited.

Finally, while the creators of Whole30 don’t market it as a weight loss diet, many followers have reported weight loss during the 30 days of eliminating. This, however, is often due to water loss and not actual weight.

Ultimately, if your goal is to eat a bit healthier, rather than putting your body through such a drastic and restrictive diet, you can do this by adding a few more fruits and veggies into your diet.

If you’re concerned that you might have food sensitivities or allergies, consider speaking to a medical professional.

Low-carb diets like keto promise quick weight loss and the ability to kick your sugar addiction to the curb. And while this might sound hugely attractive, the diet falls short in more ways than one.

Low-carb diets are defined as those that limit carbohydrates to as low as 50 grams per day and increase intake of protein and fat. Low-carb diets have been linked to treating epilepsy, though these cases are closely monitored by a medical team. Short-term studies have also shown benefits for other conditions, such as PCOS.

For starters, any diet that asks you to cut out whole food groups isn’t sustainable. You’re likely to lose out on vital nutrients in the process, too.

Carbohydrates usually make up about 50 percent of our diet. However, while you might shrug at the idea of cutting out pastas and breads, it’s important to remember that carbs also come in other forms. Fruit, dairy, and starchy veggies are great sources of carbs, too. Reducing these foods along with breads and pastas means missing out on vital nutrients, such as fiber, calcium, and vitamin E.

And ultimately, by restricting food groups, we tend to crave them more. Instead, we should enjoy foods in moderation and focus on eating more whole grains and less refined carbohydrates.

Like Whole30, paleo focuses on whole foods but with a twist: You want to eat like your ancestors did and cut out most processed foods.

Paleo requires people to focus on eating only “whole foods” like meats, fish, veggies, fruits, and nuts. Meanwhile, sugar, grains, dairy, legumes, and anything artificial are off-limits.

Because you essentially avoid most processed foods, you do see weight loss. But again, a diet like this might not be sustainable long term.

Moreover, it can be very expensive to not eat prepackaged foods, which are perfectly fine as part of a healthy, diverse, balanced lifestyle.

And although diets like paleo and Whole30 focus on making sure you cook more and eat more fruits and veggies — never a bad thing — this type of restriction can lead to negative thinking and obsession over whether foods are “good or bad.” And this is never healthy.

As my intern Maria jokingly points out, just because our ancestors couldn’t make cheese doesn’t mean you shouldn’t enjoy it — especially since it’s a good source of protein and calcium.

Eating processed foods, carbs, and dairy isn’t an end all to your health. These foods can be part of a healthy, balanced diet that allows you to reach your health goals without restriction and deprivation.

Having to restrict for small bursts of times doesn’t necessarily teach us anything about being healthy. Instead, fad diets can cause us to yo-yo diet, and this can be detrimental to our physical and mental health. It also doesn’t allow us to enjoy our everyday life with family and friends.

In short: Restrictions aren’t the way to go. Instead, follow a healthy, sustainable plan for your individual self that includes a variety of foods that satisfy your soul and make you happy as well as nourished.

Dalina Soto, MA, RD, LDN, is founder and bilingual registered dietitian atNutritiously Yours, based in Philadelphia. Dalina received her bachelor’s in nutritional sciences from Penn State University and completed her master’s and dietetic internship at Immaculata University. Throughout her career, Dalina has worked in the community of Philadelphia helping clients ditch diets and eat healthy. Follow her onInstagram.