Best weight loss diets in 2021 … and the ones to avoid

By Marisa Cohen

Turning the calendar page to a new year is often a signal that it’s time for a fresh start—and that has never felt more weicome than in 2021. After nearly a year spent staying home, stressing out, and comfort-bingeing baked goods and Netflix, many of us are looking forward to getting active, getting healthy, and taking off all those quarantine pounds in the next 12 months. “Eating a nutrient-rich diet can make us feel better and more energized, and it lets us know we are taking steps towards a healthier life,” says dietitian Amanda Beaver, RDN, of Houston Methodist Wellness Services. “It is something we can actually take action on after a year that has been totally out of our control,” she adds.

But when you start researching the best ways to lose weight, your head can start spinning with all the different “miracle” diets out there — keto! paleo! 5-2 fasting! And of course each of these has an army of true believers, who post all over Instagram about how awesome they feel giving up carbs/sugar/meat/dinner. It can be impossible to know which one to try. “The most important thing to do when adopting a new diet is to ask yourself these questions: Is it sustainable? Does it forbid certain foods including your favorites? Can you stay on this diet while socializing with your family and going to restaurants?” says Beaver.

We asked a panel of experts to sort through some of the most buzzed-about diets, and discuss the good, the bad, and the hungry. Here are their recommendations of the top 8 to try — and 4 to forget about.

#1 Mediterranean Diet

Based on the heart-healthy lifestyle of Greece, Italy, Spain, and Portugal, Mediterranean-style diets include healthy fats such as avocados, olive oil, nuts, and fish at least twice a week, plenty of beans, fruit, leafy greens, and whole grains, and even a daily glass of red wine. You can eat cheese in moderation, but limit the red meat to once or twice a week.

How it works for weight loss: Though this diet’s primary appeal is in its numerous health benefits—it can lower your risk of both chronic disease and cognitive decline — it can also lead to weight loss if you limit your calorie intake to 1,500 a day or less. Studies have found that following either a traditional Mediterranean diet or a low-carb version of it can result in weight loss of about 5-10% of body weight over 12 months. And that weight stays off — a recent British study found that for people who had lost large amounts of weight, those who consumed a Mediterranean-style diet were twice as likely to keep it off. “This diet is easy to maintain, because the food is delicious!” says Beaver.

#2 DASH Diet

The low-sodium Dietary Approaches to Stop Hypertension (DASH) Diet was designed as a way to help people control their blood pressure without using drugs, though a few books have used it as a basis for a weight-loss diet. DASH emphasizes fruits, vegetables, whole grains, and low-fat or nonfat dairy and limits saturated fat and dietary cholesterol.

How it works for weight loss: You will certainly improve your health with this diet, and if you restrict calories while following DASH’s heart-healthy rules, you can lose weight and lower your blood pressure. A recent study found of obese older adults found that those who followed the DASH diet lost weight and decreased body fat, along with many other health benefits. “DASH is one of my favorite diets,” says Meridan Zerner, R.D., a dietitian at the Cooper Clinic in Dallas. “You’re getting the anti-inflammatory, high fiber, heart-healthy benefits, and if you use a personalized, calorie-limited plan, you can absolutely lose weight.”

#3 WW (formerly Weight Watchers)

Formerly known as Weight Watchers, this diet company has been around so long, your Grandma probably tried it when she was trying to take off the baby weight. With the newest version, myWW+, you get sorted into a color-coded program that assigns you a certain number of points per day (foods are given points based on calories, saturated fat, sugar, and protein) — you can eat whatever you want within that range. You can also eat an unlimited amount of 0-point foods (most fruits and veggies and lean proteins such as fish, tofu, beans, eggs, and chicken breast fall into this category). Memberships start at $3.22 a week for a point-tracking app and digital support; $12.69 a week gets you unlimited access to meetings and a personal coach.

How it works for weight loss: Research has consistently found that WW is effective at safely taking off the pounds. A 2013 study found that dieters assigned to WW were more than eight times more likely to lose 10% of their body weight over 6 months than those trying to diet on their own. “There is a lot of evidence that using a tracking app can help you lose weight,” says Zerner. She adds that even if you stop tracking every meal, it is easy to maintain weight loss once you internalize which healthy foods are low or 0 points.

#4 Vegan Diet

Going a step further than the traditional vegetarian diet, vegans shun all animal products, including dairy, eggs, and honey. While many choose this lifestyle for ethical or environmental reasons, some people look to the vegan diet for weight loss as well. And with the new era of plant-based meats, going vegan is easier than ever.

How it works for weight loss: Just going vegan won’t necessary help you drop the weight. After all, candy, pasta, and potato chips can all fall under the vegan label without being particularly healthy or low-cal. “If you eat high-quality vegan food, like leafy greens and plant-based proteins, you can lose more weight than either vegetarians or omnivores,” says Beaver; studies confirm that those on a plant-based diet have a lower average BMI than those who eat animal products. A 2020 Australian study came to the interesting conclusion that vegans and vegetarians are more likely to stick with the diet over the long run than those on plans such as paleo, because they were motivated by ethical and moral beliefs rather than just weight-loss.

#5 Flexitarian Diet

Whereas the vegan diet goes one step beyond vegetarianism, the Flexitarian diet takes it one step back, explains Dawn Jackson Blatner, R.D., nutritionist and author of The Flexitarian Diet. “This is a very pro-plant diet, but it gives you the flexibility to have a hot dog at a ballpark, or to eat some turkey at Thanksgiving,” she says. There are no strict calorie limitations, though Blatner’s book provides a 5-week plan that provides around 1,500 calories a day.

How it works for weight loss: By filling your plate with more vegetables, fruits, whole grains, and plant proteins, and sticking with the low-cal plan, you can lose weight and improve your health. A recent review found that people who followed a flexitarian diet had lower BMIs and lower rates of metabolic syndrome than people who regularly ate meat.

#6 Intermittent Fasting

There are a few different ways to do the intermittent fasting plan: Some people eat whatever they want 5 days a week, then consume a very low calorie diet (usually around 500 calories) on the other 2 days; others restrict their eating to an 8-hour window every day. Say, eating unlimited food between 8 a.m. and 4 p.m., and fasting for the other 16 hours.

How it works for weight loss: By limiting your overall calories consumption, you’ll take off the pounds, says Zerner, who points out that there is some evidence that this diet can also increase your metabolism rate and have other positive health effects. A 2015 meta-study found that people who did intermittent fasting lost about the same amount of weight as those who did a regular calorie-restricted diet.

#7 Volumetrics DIet

Consistently rated as one of the best diets by U.S. News & World Report, Volumetrics was created by Barbara Rolls, Ph.D., a professor of nutrition at Penn State University. The strategy here is simple: Fill up on foods that provide the most nutrition for the least amount of calories. Foods are divided into four categories, from least energy-dense (fruits, non-starchy vegetables, broth-based soups) to most energy-dense (crackers, cookies, chocolate, nuts, and butter); dieters plan their meals to include as many of the lower-density foods as possible.

How it works for weight loss: The math here is simple — the fewer calories consumed, the more weight you’ll drop. A 2016 study found a significant association between low-energy-density diets and weight loss.

#8 Plant-Based Diet

Similar to a Flexitarian diet, a plant-based diet doesn’t have any super-strict rules: You just focus on eating whole foods derived from plants most of the time, with wiggle room for the occasional piece of chicken or scrambled egg. You’re basically taking the standard American diet — which features a big hunk of meat in the center of the plate, with a few vegetables scattered on the side — and flipping that around, so vegetables, fruits, beans, nuts, and whole grains, are the star of the show, and beef, poultry, fish, eggs, and dairy only make small, cameo appearances when you have a true craving.

How it works for weight loss: Plant-based foods tend to be higher in fiber and lower in fat than animal products, keeping you filled up for fewer calories. According to one large study, overweight and obese adults who followed a plant-based diet for six months lost an average of 26 pounds.

Skip these diets

Paleo Diet

The Paleo diet is still getting a lot of buzz, even though it’s nearly impossible for modern-day humans to stick with this diet over the long-term. Based on the eating patterns of our Paleolithic ancestors, this diet requires a strict adherence to foods that would have been hunted and gathered, including lean meat, nuts and seeds, fruits and vegetables. While it cuts out processed foods, it also eliminates dairy, grains, beans and legumes. “Any diet that has a glaring list of what’s not allowed is going to be very hard to maintain,” says Bonnie Taub-Dix, R.D.N., creator of BetterThanDieting.com, author of Read It Before You Eat It. “You want a diet that makes you feel balanced both emotionally and physically.” While the elimination of processed food is a good thing, the complete elimination of healthy whole grains can leave you with a shortage of important vitamins and minerals, according to the Academy of Nutrition and Dietetics.

Keto Diet

Sure, you can lose weight initially on this high-fat, low-carb diet, which puts your body into a state of ketosis — with no carbs to burn off for energy, your cells start burning off stored fat. But keeping your body in what is basically a crisis state is not a viable long-term plan, says Kristine Clark, Ph.D., a sports nutritionist at Penn State University, who also points out that the diet can lead to side effects such as headaches, muscle soreness, constipation, and fatigue.

Sirtfood Diet

Kale smoothies are suddenly hot, thanks to Adele’s recent weight loss, which newspapers have linked to the strict Sirtfood diet. The diet focuses on the powers of foods that contain a group of proteins called sirtuins, including kale, red wine, strawberries, onions, soy, parsley, matcha tea, and oily fish such as salmon and mackerel. The first phase of the diet involves a lot of green juices and restricted calories, before you move into the maintenance phase. Restricting calories will always result in short-term weight loss, but there have been no independent studies backing up this diet.
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Marisa Cohen is Contributing Editor in the Hearst Health Newsroom and a registered dietician.

Credit: Prevention Magazine