Of course, just eating plants doesn't necessarily confer health.
"A plant-based diet could include consuming large amounts of sugar, refined starch, hydrogenated oils, and soda, which would be about the worst diet possible," Willett says.
Or, take the example of palm oil, which comes from a plant but can cause inflammation in the body, which can lead to disease, says Michael Roizen, director of the Cleveland Clinic's Wellness Institute and co-author of the YOU series of books, which include YOU: On A Diet. On the other hand, eating "seven baked sweet potatoes and broccoli every night" won't get you enough nutritional variety, he says.
Roizen agrees with Pollan's aforementioned dietary prescription, but he would add to it. "Don't eat those parts of plants that have saturated fat or that are refined or changed into simple sugars," Roizen says. Also: "You can have fun with salmon, trout, and skinless poultry," he says, noting health benefits associated with these foods.
For the purposes of this package, U.S. News defines a plant-based diet as an eating approach that emphasizes minimally processed foods from plants and is built around healthy protein like nuts, seeds, beans, and tofu. It allows for modest amounts of fish, lean meat, and low-fat dairy; you might eat these on a weekly basis, for example. Red meat can have a place in a plant-based diet but should only be eaten sparingly, such as once per month.
In keeping with this definition, we selected 11 diets that fit the profile of a plant-based diet without significant tweaking. A review by our esteemed panel of academics, physicians, and nutritionists weighed safety, healthfulness, and ease of compliance, among other issues, to score the diets.
Their top-pick? The Mediterranean diet, an approach to eating that emphasizes heaps of fresh produce along with seafood, olive oil, and red wine and whose followers historically boast longer life spans and lower rates of cancer and heart disease. Dawn Jackson Blatner's Flexitarian Diet took second place with its flexible approach to plant-based eating that minimizes meat and encourages more plants. The Ornish diet, a holistic approach to health that focuses on disease reversal and includes stress-management techniques, exercise, and social support, came in third place.
However, so many of the diets profiled in Best Diets 2013 may be easily adapted to focus more predominantly on plants. "It's hard to change ingrained habits, but I think you can often slowly move in a certain direction," says Fraser, suggesting that one might consider "several meatless meals each week or maybe each day."
According to Roizen, eating right is a matter of empowerment, starting with your food shopping. "The key change you have to make is when you go to the grocery store," he says. "You're the CEO of your body ... if you buy it, you will eat it."
With the release of Best Diets 2013, U.S. News hopes to empower you with the latest advice and insight about healthy eating to help you flourish in 2013 and beyond.