It seems like every month, there’s a new “AMAZING” diet plan. Whole30, The 21 Day Fix, Teatox—the list goes on and on. But are these diets all they’re cracked up to be?

Fad and crash diets promise significant weight loss, often in a short period of time, explains the American Academy of Family Physicians (AAFP). These diets might drastically change the way you eat, restricting certain food groups or only allowing you to eat the same foods repeatedly.

They might also involve cleanses like the Lemonade Diet, where you can only drink “lemonade” made from lemon juice, maple syrup, and cayenne pepper for 10 days.

But do these diets actually work, and are they even safe? Lori Noble, MD, a physician at Penn Medicine, offers insights about why you shouldn’t fall into the cleanse or fad diet trap.

Why You Shouldn’t Fall into the Cleanse or Fad Diet Trap

They just don’t work

Cleanses and fad diets are very temporary,” Dr. Noble said. “They’re not going to help you burn calories or fat in the long run. You may see a decrease in the number on the scale, but it won’t improve your overall health outcomes.”

Weight lost during a crash diet is likely from lean muscle and water, not body fat, according to the AAFP.

When you do a crash diet, that low number on the scale doesn’t stay there for long. In fact, it’s very common to gain weight after a crash diet. “You’ve lost some weight but then go back to eating how you were before,” Dr. Noble said.

Some don’t encourage exercise

Have you seen the cleanses or diets that advertise, “And you don’t even have to exercise!” This claim should come with a big red flag.

According to the American Diabetes Association, exercise doesn’t just help you lose weight—it helps prevent regaining weight. When you exercise, the amount of fatty acid utilized by your skeletal muscles increases, which makes it easier for your body to maintain your new, lower weight.

You’re gambling with your health

Cleanses can cause some serious health risks. They can deplete your body of vitamins and dehydrate you. They can even lead to heart problems like arrhythmia—an irregular heartbeat.

If you do cleanses frequently, you can become dependent on them for bowel movements or weight loss. “If you can’t lose weight without them, it can lead to eating disorders,” Dr. Noble added.

Doing “just one cleanse” still puts you at risk for health problems. If you lose weight quickly, you can lose electrolytes, which can also cause arrhythmias, dehydration, kidney damage, and lightheadedness. This can happen in just a couple of days.

For example, if you take something to induce diarrhea and it’s not monitored by a physician, you can get dehydrated and sick immediately,” Dr. Noble said.

One size does not fit all

Remember the Paleo diet, a diet that restricts dairy, grains, sugar, salt, and legumes (peas or beans)? It might sound healthy on the surface, but the Paleo diet excludes foods that are rich in nutrients and contain important vitamins, such as vitamin D and calcium.

That can be particularly risky for people who are already at risk for bone diseases like osteoporosis, since vitamin D and calcium are vital for bone health, says the NIH Osteoporosis and Related Bone Diseases National Resource Center.

Frankly, they’re not fun

Some of these cleanses and diet plans involve “colonoscopy treatment,” where you completely clean yourself out or drink only juice for a week. This can make your blood sugar crash, among other serious problems.

I have patients come in saying they did that and were miserable,” Dr. Noble said. “I tell them, ‘I’d be miserable, too, if all I had all week was juice.’”

There are healthier alternatives

I don’t like to tell patients to ‘diet,’” Dr. Noble said. “To me, that’s just a four-letter word. I’d rather replace it with a different four-letter word: plan. There is no quick fix to lose weight quickly, so planning is so important.”

The alternatives are worth the effort

Yes, making long-term change can take a lot of effort. You have to be dedicated to changing your lifestyle.

But remember—it’s not about turning yourself into a bikini model. It’s about decreasing your risk of heart disease, protecting your kidneys, and preserving your health.

It’s about creating a lifestyle that you can live with and won’t make you miserable,” said Dr. Noble. “And most importantly, it’s about feeling good about yourself.”