Best Diets 2014: What's New

This year, we profiled the Acid Alkaline Diet, The Fast Diet and more. Here's why.

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We've added five new plans for our list of the Best Diets of 2014.

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The 32 diets U.S. News evaluates and ranks are as unique as the people who follow them. From the low-carb Atkins diet to raw foodism, each plan caters to a different type of dieter – to the person who likes structure, to the one who treasures home-cooked meals, to the working mom on-the-go.

This year, we zeroed in on five plans and approaches that either are or are becoming household names – some geared toward weight loss, and two designed to treat specific health conditions.

Here's a look at the five new additions to U.S. News' Best Diets 2014:

Acid Alkaline Diet. By helping your body control your pH through diet, you'll become healthier and live longer. So say advocates of the Acid Alkaline Diet, who argue that eating acid-forming foods – like red meat – tips your pH balance out of whack and sets the stage for poor health. In order to balance your pH, you need to make alkaline-forming choices front and center on your plate, the thinking goes. These include vegetables, fruits (as long as they're natural, not sweetened or dried), sprouted grains, almonds and lentils, and tofu and soy products. Overall, the Acid Alkaline Diet failed to impress U.S. News' panel of diet and nutrition experts. "There's no scientific research to back up any of the claims," one panelist said. "No data. No follow up. No sale." The plan ranked No. 27 out of 32 diets overall, and outscored only one other – Paleo – in the weight-loss category.

[Read: What Makes a Healthy Diet?]

Spark Solution Diet. Two weeks on this structured diet and exercise plan, and you'll be on the fast track to successful weight loss, say the folks behind the online healthy living community sparkpeople.com. You'll get 1,500 calories a day, which translates to a well-balanced breakfast, lunch, dinner and snacks – like a dozen almonds. "The Spark Solution" book provides specific recipes, food swap suggestions and other nutrition tips. If you opt for this diet, you'll complement the healthy eating with daily workouts; exercise is a key component. Expert reviews were mixed: One panelist called the Spark Solution a "comprehensive program that can lead to healthier eating behaviors," but another pointed out that there's nothing particularly novel about it. Overall, the plan tied for No. 13 out of 32 total diets, and it was judged the sixth best diet for weight-loss.

The Fast Diet. This pattern of eating is often referred to as the 5:2 diet – you eat normally for five days of the week and cut your calories to about 25 percent of normal intake on two nonconsecutive days of the week. Men consume just 600 calories on their two weekly fast days, while women are limited to 500 calories. Advocates claim that you'll lose weight – specifically fat – and reduce your risk of a host of chronic diseases. But our expert panelists expressed concern, particularly that the Fast Diet's lack of guidance could result in poor food choices and overeating on nonfasting days. One expert called it "just a gimmick" with "little science to support" it, though another acknowledged it could provide a jump-start for those who feel "stuck" in their weight-loss plans. The Fast Diet ranked No. 28 out of 32 total diets and tied for the 20th best weight-loss diet.

[Read: Plant-Based Diets: A Primer.]

Low FODMAP Diet. This approach is designed to provide relief for irritable bowel syndrome and, in some cases, inflammatory bowel disease. The theory is that if you lower your FODMAPs – fermentable oligosaccharides, disaccharides, monosaccharides and polyols, or types of carbohydrates that are difficult to digest – you'll lower your digestive troubles. The diet was developed in 2005 by researchers at Monash University in Australia, and it calls for people to remove potential triggers to digestive distress and then re-introduce them. With the help of a trained dietitian, you'll pinpoint your food intolerances and adjust your diet accordingly. Because the Low FODMAP Diet is a medical necessity for some people, and is not designed for weight loss, U.S. News profiled the diet but did not rank it.