Seven 2016 diet trends: What's smart, what's myth?

For your New Year's resolution, maybe you have vowed to go gluten-free. After all, your neighbor said it's her secret for shedding pounds and having that healthy, happy glow.

Or maybe you need a quick reboot after all that holiday eating and drinking. Wouldn't a "cleanse," of the sort touted by celebrities, do the trick? Similarly, perhaps you've been reading about how fasting a day a week helps set people on the path to a longer life.

But do these strategies and others making headlines really work? Are they actually good for you, and are they worth the attention, time and money that major life-style changes usually involve?

We checked in with health experts on the top diet trends they regularly encounter through working with clients or poring through studies. And here are their takes:

GLUTEN-FREE

Some publications proclaim the gluten-free frenzy is passe. But that's not what experts are seeing, and these same publications note that an estimated third of American adults are anxious enough about gluten that they are looking for ways to reduce or eliminate it from their diets.

"Gluten-free foods are still selling strong," says Sonya Angelone, a Marin County, Calif.-based dietitian and spokeswoman with the Academy of Nutrition and Dietetics.

But she and other experts say there is little evidence that most people need to say no to gluten - a protein humans have been consuming in wheat, barley and rye for thousands of years.

Going gluten-free is only medically necessary for the 1 percent of Americans who have been diagnosed with celiac disease, an autoimmune disorder where ingestion of gluten causes damage to the small intestines and can be life-threatening. Another small number of people have been told by their doctors they have gluten sensitivity, in which case splurging on birthday cake could trigger problems with digestion, immune and even cognitive function, adds Angelone.

Kevin Lomangino, managing editor of Health News Review, doesn't doubt people's claims that they feel better after giving up gluten, which is often associated with foods that are rich in refined carbohydrates. But it's most likely a placebo effect, he says. "It's not because there is anything bad about gluten. You feel better because you made a change."

Mary Ellen DiPaola, an outpatient senior dietitian at UC San Francisco, says going gluten-free can be challenging but there's no harm in it, if it leads people to cut back on high-calorie breads, pastas and snack foods - and as long as they replace those energy sources with healthy options like whole grains, legumes and vegetables. The problem comes when people believe that often pricey gluten-free sweets and snacks are more nutritious.

"If you're eating rice cakes all day, instead of potato chips," says Angelone, "that's not a healthy choice."

INTERMITTENT FASTING

Fasting is nothing new, with saints, ascetics and regular people choosing periods of self-denial as a path to enlightenment, spiritually and otherwise. Modern-day advocates say intermittent fasting can help reduce obesity and diabetes, improve cardiovascular health and extend life.

Popular strategies have people going food-free for 24 hours once or twice a week, skipping breakfast or eating like a "warrior" - fasting daily for 20 hours, then eating one large meal, usually in the evening.

Experts say, sure, a day of fasting each week could reduce someone's weekly calorie intake, which theoretically could help with weight loss, but overall, they discourage the practice. Its benefits haven't been proven, and it's not a long-term way to lose or maintain weight, says DiPaola.

Adds Lisa Cimperman, a registered dietitian at Cleveland's University Hospitals Case Medical Center and spokeswoman for the Academy of Nutrition and Dietetics: "From a metabolic standpoint, we know that in periods of starvation, the metabolism slows down." She adds that people are prone to overeat when they break their fast. "It just seems to set up a bad psychological game."

CLEANSES

Apparently, we can't help ourselves: We still look to celebrities for nutrition advice. Consider the popularity of "cleanse" diets, which, similar to fasting, promise quick weight loss as well as other short- and long-term health benefits.

Gwyneth Paltrow's seven-day "Master Cleanse," for example, involves a sharp reduction in food intake, supplanted by smoothies and occasional servings of "detox" fish or chicken.

Experts are generally skeptical of cleanse programs, because like fasting diets, they aren't sustainable. They also may deprive people of sufficient nutrients as well as fiber for digestion. As for the idea that we need a cleanse program to remove unhealthy toxins from our bodies, Jessica Shipley, a dietitian at Stanford's Nutrition Clinic, says: "We have organs in our body that are designed to remove toxins."

ANTI-INFLAMMATORY

Experts describe "anti-inflammatory" as a loose term that, along with "clean eating" or "plant-based" diets, is simply another way of getting at a well-established idea: Weight management and improved chances of staving off chronic illnesses - heart disease, diabetes and cancer - come with diets that stress whole, unprocessed foods, plenty of fresh fruits and vegetables, little added sugar and a balance of fish and other lean proteins, carbohydrates and "healthy" unsaturated fats.

The idea comes from Andrew Weil, the Harvard-educated pioneer in integrative medicine, who says chronic inflammation in our bodies causes the majority of chronic illnesses, such as heart disease, cancer, diabetes, depression and even Alzheimer's. The anti-inflammatory diet he created incorporates Mediterranean diet practices.

Shipley says other diet plans, which also stress portion control, serve this anti-inflammatory purpose, including the DASH, or the Dietary Approaches to Stop Hypertension, which is endorsed by the federal Department of Health and Human Services.

"There's no one size fits all that works," she says.

DiPaola cautions against making direct connections between diet and disease prevention, because diseases can be caused by a complex interplay of many factors - including genetics, environment and stress levels. Still, a healthy diet is part of a healthy lifestyle, "which can only help stave off or manage the effects of inflammatory illness or conditions," she says.

LOW-CARB VS. LOW-FAT

Over the past few years, studies have tried to settle the question of which diet is best for weight loss: one that's low in carbohydrates or low in fat? Studies seem to be swinging in favor of a low-carb approach.

But does it matter? Shipley says all diets involving restricting food in various ways can lead to weight loss. The question is whether you're comfortable saying no to bread, rice, pasta or potatoes.

"The question is, what's sustainable?" says Shipley.

"Do you like your lifestyle diet enough to feel confident you could live with it forever?" asks Yoni Freedhoff, a University of Ottawa assistant professor, blogger on weight management and author of "The Fix: Why Diets Fail and How to Make Yours Work." "If the answer's no, try something else."

PROBIOTICS AND OTHER SUPPLEMENTS

Health food stores, pharmacies and online retailers are stocked with a vast array of often high-priced pills, powders and multivitamins that promise to build muscle, help fat loss and boost your mood and immune system.

Increasingly popular are probiotic supplements, which tout their "gut" health benefits, claiming to help boost the level of bacteria in the gastrointestinal system that are necessary for good digestion and overall health.

But experts say there is no need for most people to stock up on supplements - and contribute to what the National Institutes of Health estimate is a $37 billion a year industry. Supplements are only necessary for people who have a vitamin deficiency or a health condition that makes it difficult for them to absorb nutrients.

The rest of us? We can get our nutrients from a healthy, balanced diet, Shipley says.

AN AVOCADO A DAY?

Every year it seems there are headlines heralding the amazing and surprising health benefits promised by adding one particular food to your diet.

Last year, avocados were in the spotlight, following a Journal of the American Heart Association study that said daily consumption of the creamy fruit may lower "bad" LDL cholesterol and reduce risk of heart disease.

Lomangino with Health News Review says single-food stories, like those involving avocados, often originate from studies financed by related industries. While those studies may offer valid information, they may also be limited in scope, and their results can't lead to broader conclusions about reduced health risks.

There is certainly no harm in making avocados or any other food a part of a balanced diet, Lomangino says. But there's no evidence that kale will protect you from cancer or that a daily avocado will prevent a heart attack. "The idea that there are any magic properties to any food," he says, "is pretty dubious."