8 Diets Nutritionists Say You Should Never Try

The concept of dieting is a tricky one. It's often the first thing we turn to when looking to shed extra pounds, but most of the nation’s top nutritionists don’t believe in diets as a necessary means of weight loss. While improved health, especially when certain conditions like high blood pressure, high cholesterol, and diabetes are concerned, can be achieved through improving one’s diet, committing to a certain regimen that eliminates certain food groups altogether is still considered a no-no.

In fact, Paul Salter RD, MS, a weight loss expert and sports nutritionist, believes that the term “diet” is often entirely misused and misunderstood. “In its simplest form, ‘diet’ is a habitual way of eating yet we've made it solely associated with weight loss or being in a calorie deficit,” he says. “These so-called diets are often unsustainable due to some harsh restriction or crazy, borderline ‘strategy’ to desire weight loss.” Instead, he and many other registered dietitians advocate for developing a strong foundation of consistency based on healthy choices in moderation.

Some of the worst “diet” offenders circling around society are becoming increasingly popular, often to the dismay of clinicians who specialize in health and wellness. Here are the diets that top nutritionists recommend avoiding if your goal is optimal health.


This 30-day approach to clean eating sounds wholesome and harmless enough–after all, it’s based around a commitment to eating whole foods. “The purported benefits include improving skin conditions, allergies, gut disturbances, and whole-body inflammation that are thought to be related to eating processed foods and those marked as ‘off-limits,’” explains Salter. “But the obvious downfall of this approach is that it doesn’t necessarily set you up for long-term success.” In other words, what are you supposed to do on day 31? “The creators of Whole30 suggest that you eat a ‘Whole30-ish’ diet after completing your first 30 days, and tell you to expect sugars, grains, dairy, and more to creep back into your diet,” he goes on to explain. “But without proper education about how to develop sustainable eating habits, this approach doesn’t separate itself from any other 30-day challenges, despite its good intentions and popularity.” In fact, statistics show that over 80 percent of people who lose weight regain it within 12 months with this approach.

Blood Type Diet

Popularized after Dr. Peter D’Adamo published his book, Eat Right For Your Type, back in 1996, this diet claims that your unique blood type has a strong influence on all aspects of your health. “The four different blood types, A, B, AB, and O, are so named for your body’s ability to control a specific set of antibodies, which work to identify foreign bacteria and viruses, or antigens, within the body,” explains Salter. “Someone who is born with blood type A is able to recognize that specific protein A is not a foreign invader, but that protein B is an invader; thus, the body views B as a threat and mounts an attack against it.” But research is lacking when it comes to analyzing the effectiveness of the Blood Type Diet. While, on paper, this seems like it might make sense, Salter warns that nutrition isn’t that black and white. “Most of Dr. D’Adamo’s claims are based on hundreds of anecdotes and his interpretation of the current research regarding good biochemistry and blood types,” he says. “More research is warranted, especially before you consider paying the hefty price tag to get your blood type tested, to purchase his book, and to purchase all recommended and unsupported supplements.”

Keto Diet

Also known as the ketogenic diet, keto consists of eating food that is very low in carbohydrates and high in fat, with the goal of putting your body into a metabolic state called ketosis. This is a normal metabolic process that occurs when the body does not have enough glucose to use for energy—instead, turning to burning fat stores as an energy source. While Abbey Sharp, RD, founder of Abbey's Kitchen, does believe there are a lot of potential therapeutic uses for the keto diet, she is not convinced that it is a healthy long-term weight loss strategy due to its restrictiveness. “Consuming so few carb-based foods, even fruit, pulses and whole grains, carries risks of nutrient deficiencies—not to mention constipation—if not done very carefully,” she says. “We also know that the keto diet is not great for athletic or fitness populations, so if you’re sweating it out in the gym, cutting out carbs may not be helping your regime.”

Watermelon Diet

Just as its name suggests, this diet consists of eating immense amounts of watermelon—at least 90 percent—throughout the day. “Given the high water content in watermelon, it has the ability to make you urinate a lot, thus giving you the opportunity to flush out any build up of toxins,” explains Tracy Lockwood Beckerman, celebrity registered dietitian in New York City and founder of Tracy Lockwood Nutrition. “However, if you are only eating watermelon, it can be dangerous, because in excess, it may disrupt your electrolyte balance, causing you to become overly hydrated, dizzy, and even confused.” The only take-away she can find from this diet is that replacing sugary fruit juices, sodas, and excessive desserts with cubes of watermelon is a healthier way to satisfy your sweet tooth.

Raw Foods Diet

If you’re a fan of fish and vegetables eaten as-is, this diet might sound appealing. The idea is that you eat uncooked, unprocessed, and mostly organic foods—fruits, vegetables, grains, meat, eggs, fish, unpasteurized dairy…the list goes on. But Carolyn Dean, MD, ND, a health, diet, and nutrition expert, says this diet is no good, as these foods are too “damp” for the body, can cause yeast overgrowth, and allow too much sweet fruits that can cause elevation of triglycerides. “Acetaldehyde is a powerful toxic byproduct of yeast, and magnesium is required to break it down, so, in other words, if there isn’t enough magnesium, there can be a lot of acetaldehyde side effects,” she says. “Acetaldehyde is toxic to the brain, liver, and kidneys and can cause vitamin B depletion and magnesium depletion. It also can block hormone receptors affecting the thyroid, adrenals, and pituitary.” Bottom line, cooked foods are not the enemy.

Alkaline Diet

This diet promotes foods that are said to influence acid-base homeostasis in the body (whole, raw, organic, fruits, and vegetables), explains Lockwood Beckerman. “Supporters say that the Alkaline environment within the body helps weight loss efforts, increases energy, and can boost the immune system.” While people with hypertension, diabetes, arthritis or vitamin D deficiency may benefit from this diet, the data is not there yet to support this diet for the rest of us. “It is difficult to prove that the Alkaline Diet has any real effect in pH balance,” she says. “Our body has mechanisms to keep pH levels in check, despite your diet. Plus, It can be confusing to follow, as there is no specific plan.” Additionally, the Alkaline diet restricts a bevy of healthy foods and proteins.

The Cookie Diet

Yes, this is an actual diet that involves eating a bunch of cookies specially made for weight loss, since they’re high in fiber and low in calories (but apparently taste like garbage). You get to have one “normal” meal containing vegetables and high protein for either lunch or dinner. “The thinking is that it curbs sugar cravings for those who love sweets and just want to eat cookies all day, but this does nothing to help the root cause, which is sugar addiction,” says Monica Auslander, MS, RDN, of Essence Nutrition. “Many chronic dieters need psychological therapy to tease out deeper issues here, which is why they return to dieting!”

Juice “Cleanses”

Unfortunately, “juicing” has become more than just a fad. However, fitness experts sat that the approach of losing so much weight so fast and on relatively little fuel is unsustainable. “They're marketed as quick-fix, extreme weight loss approaches and often marketed to vulnerable populations to earn a quick buck,” warns Salter. “They often create many nutrient deficiencies and further escalate poor relationships with food.” Additionally, Sharp notes that most cleanses are incredibly restrictive, low in protein and fats, and generally consist of only carbs. So, even if you just do a cleanse for a few days, you run the risk of slowing down your metabolism. “They’re also not satiating at all, so the moment you come off the diet, you’re likely to binge. With a sluggish metabolism, that’s a recipe for weight regain,” Sharp says. “They completely separate you from the pleasure of eating food and suggest that real food is ‘dirty’ and needs to be cleansed.”