Many, many food fads are just that — fads — and should fade out as quickly as possible. Here are some of the worst nutritional trends of the past year:

Eating like a caveman

The hugely popular Paleo Diet is based on the theory that our bodies are optimized for eating the foods our hunter-gatherer ancestors ate: fruits, vegetables and meat. Problem is, our lifestyles aren’t, says Andrea N. Giancoli, R.D., spokesperson with the Academy of Nutrition and Dietetics.

“It’s not like our ancestors were hunting cows or chickens,” she said. “They were hunting super-lean wild game, and most people today can’t go out and consume wild game all of the time.”

Domesticated farm animals aren’t as lean as wild game, so diets heavy in their meats include more saturated fat than is healthy. While the strict fruits-veggies-meat diet will result in weight loss by eliminating refined sugars and preservatives, results are far from sustainable, as the restrictions make the diet difficult to keep up. What’s more, by prohibiting the consumption of fiber-filled legumes and whole grains as well as calcium, it can set dieters up for cravings and nutritional deficiencies.

Bottom line: A diet based in fruits and veggies is great, as is shunning refined sugars and preservatives. But to be sustainable, diet plans need to meet all of the body’s nutritional needs, Giancoli said.

Going raw

A newfangled form of veganism, the Raw Food Diet maintains that nonplant foods are unhealthy and that plants are most nutritious when eaten in their uncooked form. While plant-heavy diets can aid in weight loss and are linked to lower rates of heart disease, diabetes and premature death, by allowing for no meats or animal products, the super-strict diet can lead to nutritional deficiency, Giancoli said. “It’s based on junk science. While cooking can destroy certain health-promoting enzymes in produce, our stomach often kills them anyway. And some of the produce eaten in the diet, while uncooked, can be highly processed,” she said. The Raw Food Diet requires a lot of dicing, slicing, dehydrating and juicing, which can decrease the quantity of nutrients, such as vitamin C and fiber, in plants, she said. Plus, all the prep just isn’t practical.

Bottom line: Fruits and vegetables are great — and best when they aren’t pulverized. Eat them whole, eat them often, but don’t live in fear of lean meats and dairy, Giancoli said.

Commercial cleanses

Juice detoxes claim that by replacing meals with fruit and vegetable juices, you remove toxins from the body and lose weight. First, the body has its own detox system known as the liver, kidneys and gastrointestinal tract, which can cleanse the body better than any juice, said nutritionist Tanya Zuckerbrot, author of the “The Miracle Carb Diet: Make Calories and Fat Disappear — with Fiber!” Second, you’re not meant to live on liquids alone. The result: You drop a few pounds of water weight during the few days of the diet cleanse and then put it all back on after you’ve finished it.

Bottom line: Feed your body all of the nutrients it needs to run optimally and then trust your body to detox itself as designed. While knocking back a bottle of unprocessed fruit and vegetable juices can be a great way to hit your five servings a day, they shouldn’t replace meals.

Running on hormones

Oh, hormones. They make us happy, sad and, according to the disturbingly popular HCG Diet, can be injected or taken in serum drops to speed up our metabolism and spur weight loss. HCG, or human chorionic gonadotropin, is a hormone produced during pregnancy (it’s what pregnancy tests detect) that is not approved by the Food and Drug Administration for over-the-counter use.

HCG supplementation hasn’t been proven to result in weight loss. However, by limiting dieters to between 500 and 800 calories a day, the diet causes extreme weight loss. Your metabolism doesn’t speed up, it slows to a crawl as it tries to preserve energy. Eventually, your body is forced to feed on its muscles which can weaken the muscles of your heart and other organs. And when you go off the diet, all of the fat will come back, but without the muscle tone you originally had, Giancoli said.

Bottom line: If a diet sounds too good to be true, the FDA doesn’t approve it, and “The Jersey Shore” crew is doing it, steer clear. “Remember the golden rule of dieting: The faster the weight comes off, the more likely you are to regain it,” Giancoli said. A balanced and healthy diet should result in no more than one to two pounds of weight loss a week.