While DASH diet may be the best overall choice for changing your eating habits, Weight Watchers won U.S. News' best diet for weight loss. The diet works by calculating a SmartPoints number based on your gender, weight, height, and age. Every food item -- and I do mean every item you can think of, including restaurant dishes -- is assigned a point value based on nutrition. Fruits and most vegetables are zero points, which helps curb the "I'm starving" feeling that sometimes starts the moment you decide to diet. Weight Watchers is also a very convenient diet, with an app and website to check point values and local meetings for in-person support. Evidence suggests Weight Watchers users are more likely to lose weight the more they use the brand's tools (and even more so if they attend meetings), and dieters lose an average of six pounds after four weeks.

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HMR is one highly regarded fad diet for those times when you're hoping to hit a goal weight quickly. You'll buy the program's prepackaged meal replacements, which include shakes, entrees and nutrition bars, and eat five servings of fruits and vegetables daily. Once you hit your weight-loss goal, you'll transition out some of the HMR food and replace with lean proteins. The popular diet also emphasizes the importance of daily physical activity, starting with a simple 10-20 minutes of walking and working up to a goal of burning 2,000 calories per week. Dieters lose an average of 23 pounds over 12 weeks, or 1-2 pounds per week. As for convenience, it doesn't get easier than food delivered right to your door, although if cost is a concern, the prepackaged meals are pricey at $265 for a starter kit and $180 to re-up every two weeks.

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Mediterranean-area countries like Greece, Italy, and Spain are already known for their delicious food, but studies suggest that similarities amongst the local diets may also lead to heart health, weight loss, and diabetes and cancer prevention. A food pyramid crafted by the Harvard School of Public Health suggests adherents eat seafood weekly, skip red wine and red meat, and limit poultry and dairy. Suggested foods include fruits and veggies, beans, whole grains and, of course, olive oil. As U.S. News points out, the Mediterranean diet is "an eating pattern, and not a structured diet," so if you're focused on weight loss, speak with your doctor about a calorie target and fitness plan. But the popular diet has been proven to help with weight loss; a study following 259 overweight diabetics on the diet found that they lost an average of about 16 pounds over a year. There are plenty of recipe options that will please the dieter and the dieter's friend who loves Italian food.

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The flexitarian diet does away with what is often the most difficult part of dieting -- restriction. Coined by registered dietitian Dawn Jackson Blatner, the term combines "flexible" and "vegetarian" for a mostly vegetarian diet with room to grab a burger when you crave meat. You'll add five food groups -- fruits and veggies, whole grains, dairy, sugar and spice, and new "meats" like tofu and lentils -- to your diet, and snack twice daily. As a vegetarian, you'll likely eat fewer calories and still feel full. Add physical activity to your regimen, and the fad diet typically leads to weight loss. Data shows that vegetarians typically weight about 15 percent less than carnivores, with a lower Body Mass Index. Let Dr. Blatner's book be your guide for recipes, advice, and shopping lists.

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The Mayo Clinic Diet will walk you through two phases, intended to jumpstart weight loss then set up a new healthy lifestyle for long-term success. In the "Lose It" phase, which lasts only two weeks, you'll work out for 30 minutes daily, cut all sugar besides fruit, and stop eating in front of the TV. You'll eat lots of healthy fats and whole grains and start your day with a healthy breakfast. "Bonus habits" include cutting out processed food. The goal is to lose 6 to 10 pounds in this diet phase. After two weeks, the "Live It" phase is more lax on the rules, and gives you a calorie count to follow to either lose more weight or maintain what you lost during phase one. This popular diet ranks higher than some others on the "challenging" scale: You'll have difficulty eating out and largely won't be encouraged to drink alcohol. But while you're reaching for the carrot sticks for the tenth time in a day, take a small comfort in the fact that the Mayo Clinic medical center is highly qualified to develop a healthy diet that works.

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