4 Reasons Fad Diets Aren’t Good for Your Health

Have you ever had a friend tell you they can’t join you for lunch because they’re in the detox phase of a new eating plan? Or seen a celebrity say that they’ve found the key to weight loss after years of struggling—and they can still eat most of what they want, with a few exceptions? Are you intrigued by a book that promises you’ll drop pounds quickly with a set of secret foods?

Fad diets are all around us, and they can be hard to resist when you’re not happy with the number on the scale.

“These diets promise rapid weight loss with a magic bullet,” says UNC Health dietitian Shelly Wegman. “If there really was a magic bullet, I wouldn’t have a job.”

Still, Wegman understands the allure of fad diets beyond weight loss.

“People are busy and overwhelmed, so it’s nice to be told what to do,” she says of diets that provide sample meals and rules to follow. “If a fad diet is appealing because of convenience, you can work with a dietitian on ideas for making healthy meals easier for you.”

Fad diets just don’t work, unfortunately, and some are harmful to your health. Wegman explains why.

1. Fad diets are restrictive and nutritionally inadequate.

Fad diets often rely on cutting out entire food groups or exclusively eating certain “good” foods. They may rely on periods when you eat very few calories. Wegman says that approach simply isn’t sustainable.

“Your body can tolerate eating few calories only for so long before it will increase your hunger hormones to get you to eat,” she says. “Psychologically, you’ll crave foods more when you can’t have them, so restriction makes it more likely that you’ll binge on something. These diets can lead to a lot of disordered behaviors and rules about food.”

What’s more, restricting food groups can lead to nutritional deficiencies. Your body needs a mix of macronutrients (carbohydrates, fats and proteins) as well as micronutrients (vitamins and minerals) to function at its best. Eliminating food groups makes it harder for you to meet those requirements.

Wegman says to be wary if a diet claims that you can make up nutritional deficiencies by taking a supplement or buying a certain kind of food from a company.

“There is minimal supervision of supplements and dietary aids, and what’s on the label may not always be what’s in the product,” she says. “Some of these power bars or snacks that are part of these diets are highly processed.”

2. Fad diets rely on short-term changes over long-term habits.

Let’s say you’re attending a big event in a few weeks and want to lose weight beforehand. You may think that attempting a diet trend that promises rapid weight loss is at least worth a shot. However, you may be setting yourself up for a dangerous cycle.

“The problem with diets is that while people may lose weight, they will regain the weight they lost and more when they go off the diet,” Wegman says. “With rapid weight loss, you’re usually losing muscle mass, which affects your metabolism and makes it easier to continue to gain weight.”

Wegman says the belly area is usually the first place you gain weight and the last place you lose it, so if you’ve been cycling through diets and seeing growth in your midsection, that may be why.

Instead of looking for short-term fixes, Wegman recommends taking sustainable steps to a long-term lifestyle by learning how to put together balanced, nutritious meals.

“Food fuels your body so you can live the life you want,” she says. “You should be able to enjoy food and benefit from what it can do for you. The best way to do that is being mindful about what you eat and honoring when you’re hungry and when you’re full.”

3. Fad diets don’t account for your specific situation.

We all process foods differently, and your body has specific nutritional needs. How can one diet plan possibly work for everyone? Spoiler: It can’t.

“Genetics controls a lot of your shape and size,” Wegman says. “You do have control over the foods you consume and the exercise you do, but some things can’t be changed. You need to have realistic expectations for what your body can do.”

A dietitian or doctor can help you understand your diet in the context of other lifestyle factors, which a fad diet may not consider. Fad diets tend to focus mostly on dietary changes and not on healthy habits such as exercising and drinking more water.

“Weight is more than what you’re eating,” Wegman says. “Sleep plays a huge role. Stress can throw off your gut and your immune system. Maybe you need to get your thyroid checked or you have a vitamin deficiency. All of these play a role in how your body metabolizes food and modulates your weight.”

Age and sex are also factors.

“At 40, you start losing muscle at a faster rate, and that can make it easier to gain weight,” Wegman says. “Menopause will have effects for women related to weight gain.”

It’s important to build a healthy lifestyle that takes all of these aspects into account, rather than expecting results from only changing your diet.

4. Fad diets are not well studied and may have long-term effects.

You might see a fad diet that was developed by a medical professional or that claims to be based on science, but Wegman says these diets usually are not rigorously tested and tend to rely on inconsistent evidence.

Even if someone has lost weight with a dietary trend, there could be long-term consequences that may or may not be known now.

“With high-protein diets like Atkins, there is an increased risk for kidney stones,” Wegman says. “A high-fat diet like keto has been linked with dementia and bad cholesterol. Unless you have a specific health issue, like a food allergy or diabetes, you really don’t need these modifications; you need balanced nutrition from a variety of foods.”

For that reason, Wegman recommends forgoing fad diets for the simplest solution: learning how to build meals with a mix of lean proteins, such as beans, lentils, fish and chicken; carbohydrates from grains and fruits; and nonstarchy vegetables, such as leafy greens, peppers, broccoli and cucumbers.

“It’s really not about eating this or that or following specific rules,” she says. “You’ll spend a lot of time thinking about food that you could spend on living your life. Learn what the body needs, and you’ll be good to go.”

Have questions about what you should eat for good health? Talk to your doctor. If you need a doctor, find one near you.