Here, experts share the diets with science-backed evidence that they work in the long-term.
Vegan! Paleo! 5-2 Fasting! The sheer number of trendy diets out there can make your head spin, and each one has its army of true believers, who post all over Instagram about how awesome they feel after giving up carbs/sugar/meat/dinner. But which one of these diets can really help you lose the weight and, more importantly, keep it off long-term? Experts talk about the good, the bad, and the hungry.
1 . Mediterranean Diet
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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. “This diet is easy to maintain, because the food is delicious!” says Amanda Beaver, RD. a dietitian at Houston Methodist.
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. “DASH is one of my favorite diets,” says Meridan Zerner, RD, 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 Freestyle (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. The newest version, WW Freestyle, assigns you a certain number of points per week (foods are given points based on calories, saturated fat, sugar, and protein)—you can eat whatever you want within that range. Most fruits and veggies and lean proteins such as fish, tofu, beans, eggs, and chicken breast are 0 points. Memberships start at $3 a week for a point-tracking app and digital support; $8.65 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.
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5 . Flexitarian Diet
Whereas the vegan diet goes one step beyond vegetarianism, the Flexitarian diet takes it one step back, explains Dawn Jackson Blatner, RD, 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, PhD, 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 . Jenny Craig
Like WW, Jenny Craig is a business—you pay to join. And like WW, it provides online and in-person support and focuses on balanced, low-calorie meals. However, with Jenny Craig you are required to purchase portion-controlled, prepackaged meals and snacks (OptaVia and Nutrisystem work on a similar model). The program, which is also available in low-carb, low-sugar, and meat-free versions, costs about $163 per week.
How it works for weight loss: A 2015 article in the Annals of Internal Medicine found that WW and Jenny Craig were the most efficient commercially available diets for weight loss. However, since you are relying on prepackaged foods, it can be difficult to sustain the weight loss once you go back to preparing your own food, says Zerner. “The good thing about meal-replacement plans is that the math is done for you, theres no guessing,” she says.”But it’s important to have a transition plan when you go off, so you don’t gain all the weight back when you’re cooking for yourself.”
9 . 2 Diets You Can Skip
Though you may have heard friends rave about how much weight they’ve lost going Paleo or Keto, diets that eliminate entire categories of healthy food (dairy, legumes, and grains on Paleo; whole grains and fruits in Keto) are impossible to sustain over the long-term, says Bonnie Taub-Dix, RDN, creator of BetterThanDieting.com, author of Read It Before You Eat It.”Any diet that has a glaring list of what’s not allowed is going to be very hard to maintain,” she says. “You want a diet that makes you feel balanced both emotionally and physically.”