Best and Worst Health Trends of 2013

Worst: Open-bar gyms

Increasingly more gyms are serving their cool-down with a side of spirits: Finish a class and you get an all-you-can-drink pass. "Alcohol during or following an exercise class is a definite no in my book," says diLeonardo, who emphasizes the need to drink water, not alcohol. Why? According to one study in the Journal of Applied Physiology, alcohol drains your muscles' levels of glycogen, their primary source of fuel. The effect: Your muscles don't have the energy they need to repair, grow stronger, and increase your metabolism. Basically, post-exercise sips negate your workout.

Worst: The Whole30 Diet

As if the Paleo Diet wasn't strict or unsustainable enough, this year people turned to the Whole30 Diet, which is basically an extremist "caveman" plan. The month-long program prohibits the consumption of fiber-filled legumes and whole grains, calcium- and vitamin D-rich dairy, and even some Paleo-approved foods like coffee, alcohol, and honey, all of which have been linked to improved health and longevity, Caspero says. While the strict plants-and-meat diet will surely spur weight loss by eliminating unhealthy refined sugars, the diet is far from sustainable—and isn't designed to be that way. So what happens after the month ends? You yo-yo. And while weight lost from extremely restricted diets is typically from a combination of fat and lean tissues, weight regained is typically 100% fat, she says.

Worst: Hot classes

This year, hot Pilates, hot barre, and even hot weightlifting classes have joined Bikram yoga in cranking up the heat. But for what? "You don't need the heat to get a good workout," says diLeonardo. One 2013 American Council on Exercise study found that increasing the temperature does not make you work any harder or burn any more calories. All of the sweat just makes you think you do, all while putting you at risk of dehydration, she says. Also, while the ACE study found that temperatures of up to 95 degrees are safe for a person with zero health issues, researchers warn that many classes turn up the temps as high as 115 degrees.

Worst: Going gluten-free for no reason

About one in three Americans are cutting down on or completely eliminating gluten, per a 2013 survey from The NPD Group. If you're one of them, read your nutrition labels. "Gluten-free foods aren't automatically better for you, and plenty of them can make you gain pounds," says Seattle-based certified nutritionist Deborah Enos. "Gluten helps to hold food together. When food manufacturers remove gluten, they add in fat and sugar to help the food maintain its shape." Plus, a 2012 review in the Journal of the Academy of Nutrition and Dietetics shows that a gluten-free diet has no benefit—and can even harm gut health—in people without celiac disease or a gluten intolerance.

Worst: Vibration machines

Remember watching your mom jiggle her fat away with vibrating belts? Well, the vibration fad is back, but this time you stand on a pulsating platform to tone muscles, boost your metabolism, and reduce cellulite…or not. In one International Journal of Sports Medicine study, women who completed 24 weeks of whole-body vibration training did not lose fat.

Worst: Too-intense workouts

Pushing yourself is great. But pushing yourself beyond your ability is counterproductive and dangerous. Unfortunately a slew of workout classes and DVDs tout exhaustion as the ultimate goal, sacrificing form for intensity and increasing your risk of injury, says performance enhancement specialist Martin Rooney. What's more, when working out at home to DVDs, it's challenging to know if you are keeping form even before fatigue sets in. Before signing up for any high-intensity interval classes (which we love!) or popping in a DVD, develop proper form with a personal or small-group trainer.

Worst: The Bulletproof Diet

An example of why you should read into who's behind your eating plan, The Bulletproof Diet wasn't drafted by an MD or nutritionist. It was designed by a Silicon Valley investor and computer security professional who lost more than 100 pounds, according to the diet's website. While his personal weight-loss is certainly inspiring, it doesn't provide rock-solid scientific evidence to support recommendations to eat 4,000-plus calories a day, not exercise, and scoop butter into their morning coffee. If it sounds too good to be true, it probably is.