The Top 10 Worst Weight-Loss Diets of 2020 may earn compensation through affiliate links in this story.
The worst diets of the year include several popular weight-loss plans.

If you recently decided to try out a new diet, you're in good company. Every year, about 45 million Americans go on a diet, spending roughly $33 billion on weight-loss products, according to Boston Medical Center. But even the most popular diets don't necessarily guarantee success — and some may do more harm than good.

Putting the latest diet fads to the test, U.S. News & World Report evaluated the top diets with the help of a panel of health experts. While the highest-ranked regimens are easy to follow, nutritious and safe for a large variety of people, the diets lowest on the list are much the opposite. For healthy weight-loss, steer clear of these 10 worst diets in 2020.

Read more: How to Find the Best Weight-Loss Diet for You

10. HMR Program

The theory behind the HMR diet is that hormone imbalances can make it difficult to lose weight.

The Health Management Resources (HMR) Program was created more than 30 years ago by a behavioral psychologist. The program sells meal-replacement shakes, bars and pre-packaged entrees and encourages followers to eat a specific combination of those foods each day along with five servings of fruits and vegetables.

The HMR Program also comes with an app to track your daily food intake and health coaches to support you along the way. Followers are also encouraged to do daily physical activity.

While the diet has some benefits, like a focus on fruit and vegetable consumption, it can make eating out with loved ones a big challenge and prioritizes meal-replacement options over whole foods, which doesn't teach followers how to make healthy choices in the long run.

Did you know that keeping a food diary is one of the most effective ways to manage your weight? Download the MyPlate app to easily track calories, stay focused and achieve your goals!

9. Optavia Diet

The Optavia diet involves using food-replacement drinks to help promote weight loss.

Created by the team behind Medifast, Optavia is a brand of pre-packaged food products called "fuelings" that contain 24 vitamins and minerals and help you stay full and nourished, according to the diet's website. And while the food powders are nutritionally sound, according to the U.S. News & World Report rankings, they aren't as beneficial — for health or weight loss — as eating unprocessed, whole foods.

Similar to the HMR Program, the Optavia can be hard to stick with, as it doesn't provide flexibility around your food choices, and the products may be too expensive for some people.

Read more: 6 Reasons You Probably Shouldn't Try the Optavia Diet

8. Alkaline Diet

The goal of the Alkaline diet is to control your body’s pH balance to protect it from disease and improve overall health.

The goal of the Alkaline Diet is to control your body's pH balance by eating more "alkalizing foods," such as fresh produce, and less "acid-forming foods," such as refined carbohydrates and meat, according to U.S. News & World Report.

Because it emphasizes fresh produce and whole foods, this diet is high in fiber, a nutrient that's slow to digest and can help promote satiety, according to the FDA. However, the Alkaline Diet has little research behind it, according to U.S. News & World Report. And due to its restrictive nature, this diet may lead to nutrient deficiencies in the long run.

7. The Fast Diet

The Fast Diet requires you to eat regularly for five days, then cut your calories down to 20 percent of your normal intake for two days.

What if we told you that there's a weight-loss diet out there that lets you eat whatever you want? The Fast Diet allows you to do just that — as long as you significantly cut calories two days a week, according to U.S. News & World Report.

For five days a week, you consume your typical daily calories. Then, for two nonconsecutive "fast" days, you restrict to either 600 calories for men or 500 calories for women.

While this diet does have few rules to follow and only involves two days of dieting, the extreme calorie restriction can be unsafe and will likely leave your stomach grumbling.

Read more: The Beginner's Guide to the 5:2 Fasting Diet for Weight Loss

6. Paleo Diet

If cavemen didn’t eat it, it's not included in the paleo diet.

You've probably heard of the paleo diet, given that it's one of the most popular diets right now. It's based on the idea that you should eat only foods that the cavemen had available. Refined sugars, grains, dairy and legumes are off the table, while meat, fish, fruits and vegetables are all fair game.

Though this diet does emphasize a whole foods-based eating regimen, it can quickly become pricey and restricts grain consumption. Whole grains, especially, are part of a healthy diet and may help reduce the risk of heart disease, stroke and diabetes, according to the American Heart Association.

5. Raw Food Diet

According to proponents of this diet, raw food contains beneficial enzymes and nutrients that promote optimal health.

The Raw Food Diet has seemingly been around for ages and can even be traced back to the 1800s, according to U.S. News & World Report. It's pretty self-explanatory: The Raw Food Diet involves eating only foods that are uncooked, unprocessed and free of pesticides. However, while whole fruits and vegetables are the spotlight of this regimen, it's nearly impossible to follow and requires extensive planning and preparation in advance.

This diet can also result in an extreme calorie deficit, as most Raw Food Diet practitioners tend to consume only about half the calories they would on a normal diet. Cutting your calories too low can cause nutrient deficiencies and slow your metabolism, according to Harvard Health Publishing. And since the diet limits meat and dairy, it can prove especially challenging to meet your daily recommended protein intake.

Read more: 4 Types of Diets to Avoid if Long-Term Weight-Loss Is Your Goal

4. Atkins Diet

The Atkins diet promises that you’ll lose 15 pounds in two weeks by limiting your carb intake to 40 grams a day.

The Atkins diet is the grandfather of low-carb dieting. By strictly limiting carbohydrates, Atkins promises steady blood sugar levels and less body fat storage, according to the diet's website. By prioritizing high-fat foods instead of carbs, your body resorts to burning fat for energy, rather than the sugars you eat, which ultimately leads to weight loss.

This diet can help you lose weight but may also come with an array of side effects, including headache, dizziness and fatigue, according to the Mayo Clinic. Often, low-carb diets can lead to nutritional deficiencies, as they tend to be low in fiber. This can cause digestive unrest, constipation and/or nausea. In the long run, lack of fiber can also up your risk for heart disease, stroke and diabetes, per the AHA.

3. Whole30 Diet

The founders of the Whole30 diet believe that many mental and physical health issues are caused by our diets.

The Whole30 diet claims to help eliminate cravings, improve energy and sleep and promote weight-loss, according to the Whole30 website. This diet involves eliminating added sugar, alcohol, grains, legumes, dairy, sulfites and baked goods for 30 days. Then, after the 30 days are up, participants can reintroduce certain food groups slowly, helping them identify which foods make them feel better or worse.

Although the Whole30 diet isn't particularly unsafe, it is restrictive and requires high levels of commitment to actually "work," according to U.S. News & World Report. Closely following Whole30 requires daily planning and meal preparation in order to successfully identify which foods do and don't work for your body.

2. Keto Diet

“Eat fat to burn fat” seems to be the mantra of this popular diet.

"Eat fat to burn fat" is the mantra behind the keto diet, which promises to help you lose weight and boost your mood, energy and mental performance. Similar to the Atkins diet, keto involves slashing carbs — encouraging followers to eat just 20 grams a day — in order to put your body into a state of ketosis, according to the Mayo Clinic. Once in ketosis, you begin to burn fat rather than carbohydrates for energy.

While it can help you lose weight initially, there's little evidence to prove that this diet is effective in the longer term, and it can cause side effects like headache and/or constipation.

Read more: 5 Possible Risks of a Keto Diet

1. Dukan Diet

This diet promises that you’ll lose up to 10 pounds in the first week.

The Dukan diet focuses on protein intake, rather than counting calories, as the key to weight loss, according to U.S. News & World Report. Like Atkins and keto, this diet is based on the idea that cutting carbs forces your body to burn fat instead. However, unlike other low-carb regimens, Dukan focuses more on increasing protein consumption.

The Dukan diet can lead to short-term weight loss, but it's an extremely restrictive regimen. While you can eat an unrestricted amount of protein and veggies, all other food groups are either curtailed or cut completely. Panelists for U.S. News & World Report warn that the diet can lead to nutritional deficiencies.

Read more: 6 Surprising Symptoms of Vitamin Deficiencies

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