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Every year, ratings groups such as Consumer Reports and U.S. News poll health experts and actual dieters to find out which diets are most effective. And year after year certain diets always rise to the top: Weight Watchers, the Dash Diet, the Mediterranean Diet, the Mayo Clinic Diet, and eating clean are among those that tend to score high for their effectiveness, ease, and safety. What common features set these and other winning diets apart from the rest? Here are five good rules the top diets all follow:

1. They Push Produce

The usual recommendation to eat five servings of produce each day doesn't cut it. We actually need seven to nine portions of fruit and vegetables a day, especially when dieting. Vegetables and fruit are fat-free and ultra low in calories. When you focus on adding produce (instead of cutting out anything), your calorie intake drops naturally and your health quotient rises, all without feelings of deprivation setting in. The Dash Diet and Mediterranean Diets are full of vegetables, fruits, and other plant-based foods.

2. They Prescribe Portion Control

Portion control is the companion of moderation. Eating until you're satiated but not stuffed is associated with feeling more energy and less distress after meals. Plus, by eating smaller portions, the body becomes conditioned to feel "full" with smaller amounts of food. The easiest way to control portions at home is by using small plates, bowls, cups, and glasses. At restaurants, order appetizers and sides instead of an entree or to share an entree with a friend. By resetting how much you think of as a serving of food, you'll automatically eat less over time.

3. They Allow Room for Treats

Research shows that rigid diets with lots rules about what not to eat are associated with eating disorders, mood disturbances, and, ultimately, failure to maintain lost weight. The good diets are flexible enough to offer opportunities to practice decision-making in the real world. Some diets call it healthy cheating, other call it a reward, others say it's everything in moderation. But no matter how a diet details this rule-bending, fitting in the occasional indulgence actually makes sticking to your diet easier the rest of the time.

By Mary Hartley, R.D., for

4. They Build in Social Support

"Monkey see, monkey do." Humans have a basic desire to mimic, and we subconsciously copy the behaviors of our friends. That's why you should expect to be as fat-or as slim-as your companions. Research shows that dieters achieve greater weight loss when they are supported by fellow dieters and healthy pals. And it doesn't matter whether supportive friends lived nearby or far away. That's why both online and in-person support groups work. Having support during failures and successes makes you feel like you're not in it alone, which can help you stick with a plan even when the going gets tough.

5. They Add More Movement

When it comes to losing weight, eating fewer calories is more important than moving more. But for keeping weight off, regular physical activity is the key. The best diet plans all promote moderate physical activity. According to the American College of Sports Medicine, around 30 minutes of exercise each day is a great place to start. Walking to work and then back home fits the bill. All of the top diets encourage this sort of exercise in their plans, and many add even more.