Fad diets and trendy workouts: what works?

Everywhere you turn, someone’s doing something she swears will change her body. Maybe the co-worker whose green-juice bottles clutter the office fridge claims she lost 3 pounds in three days. Perhaps your pal says her clothes are looser after hot yoga.

In an iEverything world, where instant gratification rules, it’s easy to think there’s a magical way to drop pounds fast. Before you guzzle, sweat yourself silly or do anything extreme, know what the experts have to say.

Juice cleanses

How they work: You order vegetable and fruit beverages from one of the ubiquitous juice-cleanse companies like BluePrintCleanse or Organic Avenue. Then, as you’ve likely heard from the friend who won’t shut up about it on Facebook, for three to five days you drink only these beverages. (If you must eat, some companies say certain foods, mostly raw veggies, are OK.)

So do they work (and are they safe)? You might shed, but it’ll be mostly water weight. “Nobody should do a juice fast for more than three days,” cautions Dr. Pamela Peeke, assistant professor at the University of Maryland and author of the book “The Hunger Fix.” No matter how many vitamins the juices have, the lack of fat means some of them won’t be properly absorbed.

If you do repeated cleanses, continues Peeke, the periods of calorie deprivation could cause a temporary metabolism slowdown. Steer clear if you’re pregnant or have diabetes. And know that you could even gain weight if you overdo it with fruit juices, adds Dr. Frank Lipman, an integrative medicine specialist in New York City. Even the healthiest fruit juice packs sugar. Case in point: Organic Avenue’s Gracious grapefruit juice has 37 grams.

If you want to try one: A three-day juice fast before a big event should be fine, allows Dr. Peeke, but check in with your doctor first. And be aware that these diets can clean you out in more ways than one: They cost up to $75 a day.

Health.com: A guide to popular juice cleanses

Hot yoga

How it works: The original is Bikram yoga, a 90-minute series of 26 poses done twice in a 105-degree studio. You’ll find other hot yoga classes – either Vinyasa or Ashtanga yoga, given in 90-degree-plus rooms. Proponents claim the high temps help boost metabolism.

So does it work (and is it safe)? “You’re going to sweat a ton, then you’re going to drink like mad and put back on all the water weight you lost,” says Peeke. As for claims you’ll burn fat faster? “Your metabolism improves, at least temporarily, with pretty much any exercise.”

And the heat may make you move less vigorously, notes B. Don Franks, a fellow of the American College of Sports Medicine: “The more work you do, the more calories you burn.” Avoid hot yoga if you have hypertension or heart disease since it can spike blood pressure.

If you want to try it: Stick with power yoga or aerobics for more effective fat-burning. But if you test out hot yoga, drink up: Bikram masters recommend an extra 64 to 80 ounces of water per day.

Health.com: Which type of yoga is best for you?

Acupuncture

How it works: This ancient practice has found new life as part of some slimming strategies. A practitioner inserts fine needles along the ear to target “hunger points” that, when stimulated, may impact hormones related to appetite.

So does it work (and is it safe)? “Only in combination with diet and exercise, and the magnitude of added benefit is not clear,” says Dr. Tieraona Low Dog, fellowship director at the University of Arizona Center for Integrative Medicine.

She suggests potential payoffs may be more likely a result of weekly interaction with the acupuncturist: “When someone is accountable, they generally have better success.” Of course, checking in with a friend could serve that purpose.

If you want to try it: Go to a reputable provider. Find a list of practitioners at the National Certification Commission for Acupuncture and Oriental Medicine’s site. Sessions cost between $50 and $120; most people go once a week.

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Alkaline diet

How it works: According to the alkaline theory, if you get your protein mostly from certain nuts, seeds and forms of soy, and eat lots of produce while avoiding “acid-promoting” high-fat animal products, sugar, caffeine and alcohol, you will promote a neutral blood pH that can help keep your body trim and healthy.

So does it work (and is it safe?) “The alkaline diet is a marketing ploy, and most of the recommendations are ones I’d give my clients anyway,” says Marjorie Nolan Cohn, a spokeswoman for the Academy of Nutrition and Dietetics. One problem with the diet: overdoing nuts, seeds and avocados, which are healthy but calorie-dense. In any case, blood is naturally pH-balanced, unless you have kidney problems.

If you want to try it: Check in first with your doctor, who can steer you toward a simpler eating plan to help you lose weight. Even if you still go for the alkaline diet, (which reportedly has many star fans, including Victoria Beckham) resist the urge to buy special alkaline water, which should come with a warning label: total BS.

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Slimming body wraps

How they work: A spa staffer applies a paste of chocolate, coffee or green tea, then mummifies you in plastic and a heated blanket for an hour.

So do they work (and are they safe)? This technique is similar to hot yoga: “You’ll put back on any weight you lose once you start drinking,” says Peeke. “But it’s perfectly safe unless you have hypertension.” Your skin might appear tighter for a couple of days afterward, as the caffeine in many of these wraps temporarily constricts skin, notes Dr. Elizabeth Tanzi, a dermatologist in Washington.

If you want to try one: Do a trial run before big events in case your skin is sensitive. Prices start at $60 (and go way up); for deals, check spafinder.com.

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Meditation

How it works: It has been practiced for centuries, but some newer versions are focused on mindful eating. You may be taught 10-minute meditations you can do anywhere.

So does it work (and is it safe)? Meditation can help with weight control, suggests initial research – when done hand in hand with mindful eating. In one small 2011 study conducted at the University of California at San Francisco, overweight women who received training in both practices maintained their weight, while the control group gained.

Meditation is believed to enhance the function of your brain’s prefrontal cortex, known as command central, boosting vigilance and determination (maybe even Zen-like calm!), while mindfulness makes you aware of every morsel you put in your mouth. Says Low Dog, “Most of us eat in a hurry, wolfing down our food without much thought to what it tastes like or if we are satiated.”

If you want to try it: Just do it! Eat slowly, savoring each bite and noting the sensations that arise.

If you overeat when you’re anxious, Lipman recommends downloading the free meditation app Headspace (on-the-go) – available for iPhone or Android – and carving out daily time to listen in.

Says Peeke, who tried meditation recently after years of doubting she could sit still (she can), “You teach yourself to look at jelly beans the way you would a puce micro mini with lamé: Maybe for somebody else, but not for me.”