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The Best and Worst Diets for Weight Loss

It's not always easy to see lasting weight loss results. Here's your guide to the best and worst diets so you know exactly what you're in for.

Weight loss isn't just a fitness goal. It's an entire industry filled with a multitude of products, exercise programs, and diets that all promise the same results. This explains why there's so much confusion about how to actually lose weight. How many calories should you consume? Should you do cardio or strength training? What supplements and powders should you take?

Amidst all the conflicting information, it's well-known that some diets are better than others in terms of long-term, sustainable, and healthy weight loss. But that same diet may not work for everyone, depending on dietary restrictions, food allergies, wellness goals, pre-existing health conditions, and other factors.

Starting a diet for weight loss begins with the decision to actually start. Deciding on which diet is a whole other story.

To help you decide between the best and worst diets for weight loss, here's what actual dietitians and doctors have to say. And for more, check out these 15 Underrated Weight Loss Tips That Actually Work.

The 5 Best Diets for Weight Loss

When it comes to dropping pounds and living your best life, turn to these trusted, expert-approved, best diets for weight loss.

The Mediterranean Diet

Mediterranean diet antipasto appetizer platter

What is the Mediterranean diet?

The Mediterranean diet is the #1 best overall diet ranked by U.S. News. It's known for being high in healthy fats like olive oil and fish. Nothing is off-limits on this diet, though some foods like eggs, poultry, dairy, red meat, and processed foods are eaten in moderation to keep saturated fat low.

Is the Mediterranean diet effective for weight loss?

Because the diet is rich in fruits, vegetables, whole grains, legumes, and nuts, the calorie distribution naturally leans toward healthier foods. This can create the caloric deficit needed for weight loss. The Mediterranean diet is not a fad diet, but rather a shift to a healthy lifestyle. It's named after the Mediterranean population, which tends to have fewer deaths related to heart disease.

Do experts recommend the Mediterranean diet for weight loss?

The American Heart Association recommends the Mediterranean diet as a heart-healthy diet, but it can also aid weight loss. Being non-restrictive, the Mediterranean diet has the psychological benefit of disrupting the vicious starve-binge cycles perpetuated by diet culture, which tends to promote restrictive, unsustainable diets that inevitably lead to failure.

"An 'eat less' mindset can set us up for a cycle of guilt when unfair expectations are not met due to the biological consequences of food restrictions, such as increased cravings," says Rachel Fine, RD, of diets with a long list of non-compliant foods. "A Mediterranean-style diet can help one build sustainable habits using a balanced and inclusive approach to eating, which can further help one achieve the weight goals they are aiming for."

A Plant-Based Diet

green plant based dinner with vegan diet supplements

What is a plant-based diet?

A plant-based diet is much like a vegan diet with one major difference: It emphasizes whole, unprocessed plants, so processed vegan foods aren't encouraged. The foods consumed on a plant-based diet are predominantly fruits, vegetables, nuts, seeds, grains, legumes, and soy protein.

Is a plant-based diet effective for weight loss?

Because a plant-based diet is associated with lower BMI, it's no surprise that it's effective for weight loss. Research has shown that a plant-based diet is an effective treatment for obesity.

One study even found that following two simple rules—eliminating animal products and reducing oils—encourages steady, long-term weight loss without restricting calories or exercising.

Do experts recommend a plant-based diet for weight loss?

Monisha Bhanote, MD, recommends a plant-based diet for weight loss as well as its other benefits: lower blood pressure, blood sugar, cholesterol, and risk of chronic diseases.

"One of the reasons a plant-based diet can help with weight loss is because this diet is packed with fiber. Fiber can help fill you up without adding extra calories," says Dr. Bhanote. "Removing animal products, such as meat, dairy, and eggs, also removes a significant amount of fat from your diet."

The Engine 2 Diet

Veggie burger

What is the Engine 2 diet?

The Engine 2 Diet takes a plant-based lifestyle to the next level. In addition to eliminating animal products, the diet restricts oils, processed foods, added sugars, and added salt. Followers stick to whole foods like grains, legumes, fruits, vegetables, nuts, seeds, tofu, and tempeh.

Is the Engine 2 diet effective for weight loss?

The Engine 2 diet is more restrictive than a traditional vegan diet, but if weight loss is your goal, this diet gets the job done in a healthy way. It's low in fat, yet rich in fiber, vitamins, and minerals, according to U.S. News.

Do experts recommend the Engine 2 diet for weight loss?

One of the main reasons why the Engine 2 diet is effective for weight loss is that it's high in fiber. Increasing your fiber content to at least 30 grams per day can help with weight loss, according to an Annals of Internal Medicine study.

According to Hillary Pride, RD, "The heavy focus on fruits, vegetables, legumes, and whole grains of the plant-based Engine 2 Diet means you will be consuming plenty of fiber, which has been shown to increase satiety and promote weight maintenance."

A Flexitarian Diet

Half plate veggies

What is a flexitarian diet?

If you're hesitant to go full vegan but still want to dip your toes in the trend, consider a flexitarian diet. It's exactly what it sounds like: mostly vegetarian but with the flexibility of consuming animal products when desired. Because the diet is so flexible, there are no set rules, restrictions, or must-eat foods. Much like the Mediterranean diet, a flexitarian diet encourages consuming foods in moderation with nothing being strictly off-limits.

Is a flexitarian diet effective for weight loss?

A fully vegan diet has been shown to aid weight loss, and a flexitarian diet has many of the same properties. In fact, research indicates that a flexitarian diet has health benefits related to body weight, metabolic health, blood pressure, and reduced risk of diabetes.

Do experts recommend a flexitarian diet for weight loss?

Being flexible with your diet prevents the feeling of failure and minimizes the feeling of deprivation from foods you love. "Physical, mental, and emotional satisfaction are key on a weight-loss diet so that the approach can be sustainable and help someone reach their goal in a sane and healthy manner," says Jessica Cording, RD.

According to Cording, a flexitarian diet has the added benefit of encouraging weight loss while also allowing the occasional consumption of foods that would normally be restricted. This can be the difference between success and failure and makes someone more likely to stick to their weight management regimen long-term.

The Ornish Diet

Vegetarian meal prep with italian peppers zucchini mushroom

What is the Ornish diet?

The Ornish diet has been around for a long time, so its popularity has been buried by newer diets. However, modern-day dieters shouldn't sleep on this way of eating because it grants you the power to eat unlimited amounts of compliant food groups. These buffet-style foods include fruits, vegetables, grains, and legumes. It's a low-fat diet, so animal products high in fat, such as meat and dairy, are eaten in moderation.

Is the Ornish diet effective for weight loss?

The Ornish diet has always been categorized as a heart-healthy diet. It not only reduces the risk of heart disease, but it can actually reverse heart disease through diet and lifestyle. This way of eating also lowers blood pressure and cholesterol levels.

In terms of weight loss, the Ornish diet can be just as effective as all its other health benefits. Unlike low-carb diets, the Ornish diet is high in carbs. However, complex carbohydrates are the good kind of carbs, and they don't inherently cause weight gain like processed carbs because they're higher in digestion-slowing fiber.

Do experts recommend the Ornish diet for weight loss?

The Ornish diet is recommended to people for a variety of benefits, including sustainable weight loss. "The Ornish Diet can encourage weight loss since it shuns most processed foods and encourages whole, unprocessed foods, lots of high-quality proteins and fiber, which can leave people feeling full on less energy and ultimately lead to weight reduction," says Monica Auslander Moreno, RD.

"It also encourages exercise and stress management, which can assist with weight loss. Unlike other diets, it doesn't allow for rampant access to full-fat foods. Portions of healthy fats (nuts, avocado, olive oil, etc.) are explicitly detailed to avoid inadvertent high energy intakes even from healthy fats," Moreno explains.

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The 5 Worst Diets for Weight Loss

Experts discourage following one of these worst diets for weight loss because they come with unsafe side effects long-term.

The Keto Diet

Keto meal avocado egg boats with bacon

What is the keto diet?

The keto diet is a strict low-carb diet. In fact, followers consume less than 10% of their calories from carbs. In many cases, carbs are restricted to fewer than 5 percent of daily calories. The majority of calories, between 65-80 percent, come from fat, leaving 15-25 percent for protein. In order to achieve these specific macronutrients, followers tend to pile on high-fat animal products like bacon, butter, ghee, eggs, and cheese.

Is the keto diet effective for weight loss?

Keto isn't just a clever name for a fad diet. It's short for ketogenic, which is based on the body's proven function (aka ketosis) to burn fat when carbs aren't available as an energy source. Using the keto diet for weight loss is complicated because many people tend to lose weight quickly, though the weight is likely to be regained once followers return to their normal eating patterns. There are also health concerns associated with very low-carb diets.

Do experts recommend the keto diet for weight loss?

Despite its popularity among people looking to lose weight, there are many concerns about whether the keto diet is safe. For that reason, keto isn't popular among health professionals for several reasons.

Dr. Bhanote is particularly concerned with the keto side effects: indigestion, constipation, kidney stones, and flu-like symptoms. Dr. Bhanote is also not a fan of diets high in saturated fat, like the keto diet, which can have negative consequences for cardiovascular health.

"The keto diet is not a sustainable diet or a long-term solution, and most people regain the weight once they return to eating carbs," says Dr. Bhanote. "The back-and-forth fluctuations with unsustainable fad diets can cause long-term effects on your gut microbiome and your relationship with food."


herb spice seasoned salmon

What is Whole30?

Like the name suggests, the Whole30 diet is a 30-day program that emphasizes some whole foods while eliminating others, including alcohol, sugar, legumes, grains, dairy, and processed foods. It's a restrictive diet that promises to change your life, but in the process, Whole30 eliminates foods that are known to be good sources of many nutrients.

Is Whole30 effective for weight loss?

Followers of Whole30 can lose weight on the program, but it's a trade-off. The plan encourages lots of veggies, some fruits, and moderate amounts of animal protein from meat, seafood, and eggs. However, it's not backed by science, so eliminating foods like grains and legumes is likely unnecessary for weight loss.

Do experts recommend Whole30 for weight loss?

Though the diet may be recommended for people who would benefit from removing high-glycemic foods from their diet, Whole30 isn't for everyone.

"Legumes and grains are packed with high-quality nutrients like vitamins, minerals, fiber, and protein. There is no evidence that supports eliminating these foods on Whole30," says Dr. Bhanote. "When these foods are reintroduced, it may also introduce a food sensitivity. The only benefit of these restrictions is that you cut sugar, dairy, and alcohol, which have all been linked to diseases."

A Juice Cleanse

bottled juices

What is a juice cleanse?

If you love green juices and green smoothies, a juice cleanse sounds like it would be right up your alley. A juice-only diet is notoriously low in calories yet high in fruits and vegetables. On a juice cleanse, participants eliminate solid foods and even some food groups like meat and dairy. Many juice cleanses are short-term, but some people stick to them for weeks. However, a juice cleanse is not a sustainable way to lose weight because it's low in many nutrients and leaves followers feeling deprived.

Is a juice cleanse effective for weight loss?

The effectiveness of juice cleanses remains controversial. Because they tend to be low in calories, followers may lose a small amount of weight within a couple of days. However, in reducing calories, juice cleanses also reduce vital nutrients and benefits of solid food. Eliminating solid foods for weight loss isn't a compromise that many experts would recommend.

Do experts recommend a juice cleanse for weight loss?

Juice cleanses remain one of the most unsustainable diets for weight loss because it goes against our biological motivation to chew food. The low fiber content in juice can also cause digestive discomfort, which is bad news because an unhappy gut can hinder weight loss.

According to Cording, "Juice cleanses tend to be low in fat and protein, making them unsatisfying, setting you up to be hungry and irritable. All of these things can mess with energy and mood. When someone goes back to eating normally, it's easy to regain the lost weight."

The Paleo Diet

Paleo diet food

What is the paleo diet?

Before there was keto, there was the paleo diet. High in protein and modeled on prehistoric human diets, the paleo diet consists only of foods that were available during the Paleolithic era: lean meats, fish, vegetables, fruits, nuts, and seeds. This means that grains, legumes, dairy, sugar, salt, potatoes, and processed foods are not compliant.

Is the paleo diet effective for weight loss?

At a glance, it's easy to see why people would turn to the paleo diet for weight loss. The paleo diet focuses on fresh foods and cuts back on processed food. However, much like Whole30, there are unnecessary restrictions, such as eliminating grains, legumes, and potatoes, which can all be incorporated on a weight loss plan. As with any diet with many restrictions, the paleo diet may be difficult to stick to long-term, and therefore unsustainable for steady weight loss.

Do experts recommend the paleo diet for weight loss?

Experts have difficulty getting behind diets with a laundry list of food restrictions. When severe food restrictions are in place, followers may experience feelings of guilt or failure when they consume those foods.

"For example, if you're starting a paleo protocol with the goal of shedding weight but you love adding beans, whole grains, and dairy to your currently varied diet, having to avoid these off-limit foods might stall your weight loss efforts by making adherence difficult and unpleasant," says Pride.

"Along the same lines, if a diet has a list of 'good' and 'bad' foods, a mindset that the 'good' foods can be eaten in abundance may lead to overconsumption of high-energy foods, thus hindering weight loss," she adds.

Weight Watchers

Weight watchers

What is Weight Watchers?

Having been around for ages, many people have tried and tested the Weight Watchers system for themselves. If you haven't seen the commercials, Weight Watchers is essentially a points system. Instead of counting calories, you count points. Because foods are given a certain number of points and followers adhere to a certain number of total points, nothing is off-limits. You can even have cake and processed food on Weight Watchers as long as you stay within your allotted amount of points.

Is Weight Watchers effective for weight loss?

The points system is essentially a metaphor for calories, which means that Weight Watchers is a calorie-restricted diet in disguise. When followed to a T, followers may see weight loss results, which are due to the implementation of a caloric deficit. However, following the protocol and keeping track of points is no easy task.

Moreno says that "Weight Watchers can be complicated if math isn't your strong suit with points/calculations. Over the years, it's become less structured, which can also leave people confused and prone to overindulgence at times."

Do experts recommend Weight Watchers for weight loss?

While celebrities are quick to recommend Weight Watchers, health professionals are not. The program encourages a caloric deficit, but doesn't teach its followers how to adhere to a healthy lifestyle.

"Weight Watchers encourages healthy food selections, but it also pushes a lot of its branded products like desserts, which can be highly processed with refined flours and added sugars that can inhibit weight loss," says Moreno. "It's also a bit misleading with unlimited foods that are 'zero points,' which may encourage some to binge or overeat."