In an age when diets are as trendy and transient as the latest Swedish buzzword, it can be hard to discern between sustainable plans and short-lived fads. According to Lauren Kelly, MS, RD, CDN, founder of Kelly Wellness, making this distinction is crucial. "A fad diet is something that doesn't have real concrete evidence of success," she says. "A sustainable healthy eating plan is something with research backing it showing there have been long-term benefits to following."
While a slew of new diets emerges each year, Kelly cautions against experimenting with unsubstantiated plans. "One of the most common repercussions is the depletion of important nutrients that we need to function at our best," she explains. "Also, if we make large dietary changes, we can alter our gut flora, [which] is crucial for our digestive system and immune health."
So how do you know which diets are credible and which to avoid? "Overhauling your lifestyle to fit a diet is likely not going to result in as much success as finding a diet that fits into your current lifestyle best," she advises. Here, Kelly gives an honest, informed review of the most talked-about diets so you can find the best option for your lifestyle.
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The Mediterranean diet replicates the traditional eating plan followed by people who live in countries along the coast of the Mediterranean Sea, like Greece and Italy. It embraces foods that are naturally abundant and has few restrictions.
"The Mediterranean diet emphasizes a plant-based diet, rich in vegetables, fruits, legumes, nuts and seeds, as well as extra-virgin olive oil and a few weekly servings of fatty fish and eggs," Kelly explains. Few foods are off-limits, but the diet is free of processed products and "is limited in dairy (particularly cheese such as parmesan and mozzarella), red meat, and sweets."
This is one of the best diets you can follow, says Kelly. "There's a great deal of research to support the Mediterranean diet," she says. Research shows it can be "effective in improving heart health and reduce the risk for stroke, heart attack, and dying from heart disease. It's also shown promise in reducing the risk of developing type 2 diabetes, and aiding in weight loss."
The takeaway: "There really are no major downfalls in regards to this diet, as long as we keep the portions in the recommended servings," says Kelly. Limit your nut intake to two cups per day, and indulge in wine in moderation.
This diet is modeled after our prehistoric ancestors and takes a "back to basics" approach to healthy eating. The purpose is to return to a diet that's similar to what early humans ate before modern farming and mass-produced foods.
If you're unsure what you can eat on this diet, ask yourself whether the food was available to cavemen. Anything that's been processed or refined is generally off-limits.
"The Paleo diet promotes non-starchy vegetables, fruits, nuts, seeds, and high-quality protein that include wild-caught fish, organic poultry and eggs, as well as grass-fed red meat," says Kelly. "Sugar, processed foods, dairy grains, and legumes are prohibited."
"The Paleo diet can be helpful for people with type 2 diabetes, those with or at risk for heart disease, and people trying to lose weight," says Kelly. "I would only say to add in some legumes, which are a great source of fiber to help promote gut and, therefore, immune health."
The 5:2 Diet
The 5:2 diet recommends eating normally for five days of the week, then restricting your calorie intake for two consecutive days. We hear you: Fasting hardly sounds like a healthy suggestion, but a growing body of research suggests it could improve your heart health and metabolism.
This diet focuses on when you should eat, rather that what should eat. Those who follow the diet eat normally for five days (adhering to the recommendation of 2000 calories per day) then curb their eating for two days, consuming only 500 calories.
Don't scoff at this eating plan—Kelly says there's a decent body of evidence to support it. "Research shows that it can be helpful for weight loss, as well as improving markers of heart disease and diabetes," she says, giving it a rating of six out of 10.
"It's crucial that followers of this diet do not binge during periods of eating," she warns. "We also don't want to promote starving yourself, as this can actually slow down the metabolism, making it more difficult to lose weight now and in the future."
The purpose of this diet is to "reset" your body by eliminating different food groups for a month. Kelly explains, "The concept is that you remove sugar and some other inflammatory foods, to help calm the inflammation in your body and reduce cravings. After 30 days, you would reintroduce the removed foods one at a time and note if you experience any negative symptoms."
This diet is surprisingly restrictive. You're encouraged to completely cut out sugar, alcohol, grains, legumes, and dairy from your diet.
So what can you eat? "It promotes whole foods like vegetables, fruit, nuts and seeds, [and] eating red meat, which has been linked to both heart disease and cancer," says Kelly.
"Not much scientific research has been done on the Whole30 diet," says Kelly, who is dubious about its long-term benefits and overly restrictive rules that prohibit legumes, which is "one of the healthiest groups of foods out there!"
"It may be helpful for people trying to lose weight and make other positive health changes, particularly if they are currently eating a diet high in added sugar and processed foods," she says. "However, I would recommend it only under the supervision of an MD or RD so the reintroduction phase is clear, and long-term changes can be made."
The bottom line: Don't try this at home without expert advice.
The Dukan diet focuses on weight loss and suggests that eating a protein-rich diet is the key. You're encouraged to eat as much protein-packed food on the approved list and follow a four-phase process.
Anything with protein. Foods like lean beef, pork, chicken, eggs, spices, and non-fat dairy are all fair game.
"I cannot think of a reason why I would recommend the Dukan diet over other options such as Mediterranean diet," says Kelly. "The '100 Foods Allowed' list doesn't seem to have concrete scientific basis and doesn't include some truly healthy foods like blueberries."
Next up: 15 metabolism-boosting foods to jump-start a healthy diet.
This story was originally published on March 15, 2017, and has since been updated.