What You Should Know Before You Try That Trendy Diet

It can be enticing to jump on the latest diet fad that promises weight loss and better health. But it can be difficult to discern if it's the real deal or a passing trend that may do more harm than good. That's why knowing why fad diets don't work can help you settle on a safer eating plan instead.

"It can be challenging to spot the difference between a fad diet and a legit one, especially at the height of its popularity," Maggie Moon, RD, a Los Angeles-based dietitian and author, tells LIVESTRONG.com.

Whether it's low-carb, low-fat, all bananas or no grains, a fad diet is often restrictive and makes promises it can't keep.

Here, learn what to look for when it comes to trendy weight-loss plans — and which to avoid altogether.

If it promises quick weight loss in a seemingly gimmicky way, chances are you're looking at a fad diet. These trendy eating plans usually develop a significant following quickly, which often retreats just as suddenly in search of the next latest and greatest weight-loss method.

There are a few telltale signs that a diet is nothing more than an empty promise, Moon says. These red flags include:

One example of a popular fad diet is the Atkins diet, named after cardiologist Robert Atkins.

It takes the concept of a high-protein, low-carb eating approach to another level, with a complicated four-phase plan that starts off with very few total carbohydrates (including those from fruits and vegetables), but no cap on saturated fat. (It does, however, limit added sugars and refined grains, which is in line with the 2020-2025 Dietary Guidelines for Americans.)

The severe restrictions on carbs, though, "furthers the misconception that carbohydrates promote weight gain and advocates a prolonged state of ketosis, which can be both unsustainable and harmful for long-term health," Denine Marie, RDN, Barcelona, Spain-based founder of Health Out of Habit, tells LIVESTRONG.com.

Although short-term weight loss is likely on the Atkins diet, your heart health, general nutrition and sanity are better served by a less restrictive diet plan, Marie says.

The Master Cleanse is a fad diet example in this category, Moon says. The diet of hot water mixed with lemon juice, maple syrup and cayenne pepper claims to help you lose weight and cleanse your body of toxins, restoring you to optimum health.

And this one has some star power behind it: It's the diet that Beyonce reportedly used to drop weight for her role in ​Dreamgirls​. But according to Marie, juice cleanses like this aren't all they're cracked up to be, and are one of those fad diets that don't work.

"They are not necessary to 'detox' your body or promote health," Marie says. "Your kidneys and liver naturally detoxify your body, so focus on eating nourishing foods regularly rather than using juice cleanses to compensate for inconsistent or poor eating habits."

There are no magic pills when it comes to weight loss, Moon says. Period.

Diet pills promising lightning-fast weight loss became popular in the 1980s. But many of these appetite-suppressants contained phenylpropanolamine (PPA), which was later linked to stroke in young people assigned female at birth, according to the U.S. Food & Drug Administration (FDA).

The FDA removed PPA from all drug products in 2000, thankfully. But keep this in mind: The FDA does not ensure the safety of dietary supplements before they go to market, so there's no guarantee that any weight-loss pill you take is safe, contains the ingredients it says it does or produces the effects it claims.

"My recommendation is to focus on making healthy choices a part of daily habits," Moon says. "It's not as sexy as a magic pill, sure, but it's much more effective (and sane) in the long run."

According to the Mayo Clinic, a safe rate of weight loss is 1 to 2 pounds per week, which means cutting out a max of 1,000 calories per day.

Very-low-calorie diets, like the cabbage soup diet — which encouraged followers to eat only cabbage soup for seven to 10 days and was popular with brides-to-be in the 1960s — are not realistic for long-term weight management, says Mandy Enright, RDN, a New Jersey-based registered dietitian nutritionist.

"While the weight may come off quickly, it won't stay off," she says.

Not only that, but the general lack of protein and calories in these diets can lead to fatigue, light-headedness and gastrointestinal symptoms, Enright says. And severely restrictive diets can be particularly dangerous for people who have an underlying medical condition or take prescription medications.

Fad diets can also pose risks to your long-term health and wellbeing. Here's why fad diets typically don't work:

Fad diets may help you lose weight quickly, but that weight is just as quick to return once you go back to your old eating habits. In fact, according to the Centers for Disease Control and Prevention, research shows that people who lose weight gradually and steadily (about 1 to 2 pounds per week) are the most successful at keeping it off.

Why? These diets generally fail to teach you sustainable eating habits for the long-term. That's why one-third of all weight lost with a diet is regained within one year, and most is regained within three to five years, according to the American Council on Exercise.

Fad diets are often nutritionally lacking, especially those that cut out an entire food group or groups, which is another reason why fad diets don't work in the long-term when it comes to overall health and weight loss, according to the Cleveland Clinic.

Instead of following a balanced diet, you follow a highly restrictive one that can be hard to adhere to for any length of time, per the Cleveland Clinic. If you fall off the wagon — which is almost inevitable when you're so restricted — you may feel like weight loss is not within your reach.

And the kicker: Many fad diets don't encourage exercise, which is an essential element of any healthy lifestyle, says Mark Hyman, MD, family physician, author and director of the Cleveland Clinic Center for Functional Medicine.

Dieting statistics show that losing weight requires developing beneficial habits and sticking to them consistently. Any diet that tells you otherwise will be gone tomorrow, replaced with the next best thing.

Per the American Heart Association (AHA), the best way to lose weight is with a portion-controlled diet that emphasizes the following foods along with regular physical activity:

• Fresh vegetables and fruits
• Whole grains like whole-wheat bread, brown rice and oatmeal
• Nuts
• Legumes like lentils, beans and peas
• Skinless poultry like chicken and turkey
• Fish
• Low-fat dairy products like yogurt, milk and cottage cheese

The Mediterranean diet, for example, is an eating style that prioritizes these ingredients and can help with weight loss. It can also promote heart and brain health, according to the AHA. The same goes for the Nordic diet, which includes lots of fruits, vegetables and fish, and can contribute to weight loss, per the Cleveland Clinic.

Dr. Hyman agrees that avoiding processed foods, particularly those containing added refined sugars and flours (think: packaged snack foods and desserts), and emphasizing quality, whole foods instead can help you find your "happy" weight.