Four lessons to learn from the best weight loss diets

At the start of every year, the US News and World Report assembles a panel of experts to rate the best diets, based on scientific evidence, nutrition recommendations and good old common sense.

The lists of best overall and best weight loss diets is exhaustively thorough and well worth reading. But even if you don't sign up to a particular eating plan, there's nevertheless plenty to learn from factors shared by the top five weight-loss diets:

1. Weight Watchers diet: Follow this classic diet and you'll be limited to a certain number of "points" you can eat every day. High nutrient foods generally have less points, while low-nutrient foods have more.

2. Volumetrics diet: Pioneered by Penn State University nutrition professor Barbara Rolls, this diet favours foods that less energy dense — that is, those lower in calories.

3. Jenny Craig diet: Another classic diet that limits calories by putting members on tight meal plans, then gradually teaching them how to make smarter and more nutritious food choices.

4. Vegan diet: Sayonara, foods that come from animals — regardless of whether or not the animal survives.

5. Flexitarian diet: A less extreme version of veganism and vegetarianism, flexitarianism (aka semi- or weekday vegetarianism, reducetarianism or lessetarianism) is rooted in plant-based foods with allowances for animal products.

They're varied and balanced, not punishingly restrictive

Any weight-loss diet has to be a little restrictive: to lose weight, the number of calories you burn as energy has to be higher than the calories you eat, which means eating less food.

But not drastically less food, because an eating plan that cuts calories too much isn't sustainable. You need to eat enough food to keep off hunger, and take a flexible approach that factors in occasional splurges and restaurant visits.

Weight Watchers is focused on sensible portions of sometimes foods, while Volumetrics encourages smart swaps rather than cutting favourite treats: for example, homemade pancakes made with whole-wheat flour, raspberry sauce and fresh fruit.

Even Jenny Craig, which restricts newcomers to prepackaged meals and snacks, makes allowances for small portions of desserts to manage cravings. All top five diets permit alcohol in moderation.

The takeaway: don't stop eating your favourite foods. Instead, try to eat them less often, in smaller portions, or made from more nutritious ingredients.

They're focused on the long term

Fad diets usually promise fast weight loss, and there's a reason those promises sound too good to be true.

Rather than guaranteeing you'll drop 10kg in a week, the top rated weight-loss diets are focused on slow-and-steady progress: they typically suggest you'll lose up to 1kg per week, a rate considered safe by most health experts.

They focus on whole foods, not cutting out entire food groups

Obviously veganism and (to a lesser degree) flexitarianism are exceptions, but in general the top weight-loss diets don't forbid entire food groups.

Instead of cutting things out, the diets mostly embrace whole foods — that is, those that have been minimally processed, with a particular focus on vegetables and fruit, as well as whole grains, non-fat dairy, and lean meat. (And the diets don't rely on exotic or expensive superfoods — their ingredients are things you can source at a regular supermarket.)

That focus on whole foods and the nutrients they deliver mean that, for the most part, the diets conform to government diet recommendations. The exception is veganism, which can meet nutrition targets but demands a little extra planning to do so. (Click here for some advice on how to do that.)

They demand a bit of hard work

Starting one of the best weight loss diets doesn't mean you'll lose weight. They're not miracle cures, and while they all share a simple premise — reduce calories, fat and portion sizes — that can be difficult to put into practice.

Weight Watchers adherents must count points. Volumetrics requires "lengthy meal preparation" and mental gymnastics to understand its energy density concepts. Vegans might find it tough find a decent meal when they eat out with friends.

Ultimately, the best diet is whichever  one you find easy to follow, delivers you results, and you can stick to over the long term.

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