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How to Spot a Fad Diet: The Potential Danger to Your Health

Jennifer Hanes MS, RDN, LD

Warning: This post includes discussions of weight loss, dieting, food policing, and food faddism.  Discussing the content, intent, and restriction of fad diets is an important topic, but can trigger eating disorder thoughts and/or behavior. Skip this post if needed!

In today’s society, weight loss and dieting are often top priorities for many people. Unfortunately, we live in a society that sometimes values thinness over health, often assigning desirable traits to people that are thin and negative traits to those in larger bodies, even without ever speaking to that person.

This emphasis on weight and shape as a value judgment often leaves people desperate to lose weight.

With the abundance of information available on the internet and social media, it can be difficult to distinguish between evidence-based nutrition advice and fad diets.

Fad diets, which promise quick and dramatic weight loss results through strict rules and restrictions, can be appealing in the short term but often do more harm than good in the long run.

Some fad diets can be downright dangerous or just plain ineffective. That’s why it’s important to know how to spot a fad diet from a mile away.

In this blog post, we will discuss how to spot a fad diet and the potential dangers they pose to your health. We will also provide tips for identifying and avoiding fad diets and encourage you to prioritize your health and well-being over the latest diet trend.

The Characteristics of a Fad Diet

Fad diets tend to be easy to spot once you know what you’re looking for. There are a few claims, red flags, and other identifiers that you can see in any number of fad, dangerous, and/or expensive diets you may come across.

Common phrases you’ll hear from someone peddling a fad or dangerous diet include:

  • “Your doctor doesn’t want you to know” 
  • “This new discovery” or “new breakthrough”
  • Claims that they are the only one that knows something. 
  • Claims that they are the only one that understands something.
  • “You’ve been told the wrong thing your whole life!”
  • Claims or implications that they know everything about their topic

Let’s take a look at the most common red flags and patterns of a fad diet.

Quick and Dramatic Weight Loss Promises

This is always the biggest, loudest, and boldest claim.  Sure, they may later claim you can have more energy or that some other aspect of your life may improve.

But first, they have to convince you that your biggest problem is your weight, that nothing will improve until your weight come down, and that only they can get your weight down by a lot very quickly.

One of the problems is that when you lose weight very quickly, you very rarely lose any fat stores. Instead, you are losing water, carbohydrate (read: energy) stores, and then muscle mass.

Another problem is that after watching their ad or reading their book, you now feel like your weight is unilaterally tied to your worth AND that any failure to achieve or sustain weight loss is your fault, not the fault of their shitty diet.

Restriction of Entire Food Groups or Macronutrients

This can be very blatant or very subtle.

In the 80s, we had super low-fat diets, and since the 90s, carbohydrates have been persona non grata. These are examples of blatant demonization and restriction of a major nutrient.

More subtly, certain foods are restricted under the guise of healthy eating, almost the opposite of a health halo. You see this in Tom Brady’s demonization of nightshades or Steven Gundry’s fear-mongering around lectins.

The harm in this is that while they aren’t specifically stating that certain nutrients are a problem, they are eliminating nutrients all the same. Tom Brady’s diet reduces diversity in our diet, eliminating some of the vegetables most people are willing to eat, including some foods that are very culturally important. 

Along with the loss of variety in our food, those eliminating nightshades could potentially be reducing their fiber, potassium, vitamin C, and lycopene intake.

Avoiding lectins can lead to a reduction in fiber and protein intake. So not only do you have no positive effect of eliminating beans and some other vegetables, but you cut out a major source of food for your gut microbiome and a nutrient that many vegetarians need to pay attention to.

Advocates for Specific Products or Supplements

When the entire explanation or education of the diet culminates in a sales pitch, you should be aware. 

Do you have to buy their book, their “specially formulated” supplements, or some other product to be a success with their plan? That’s a good indicator that your bank account is more important than your health. 

Products that claim to boost your metabolism, block or burn carbs, or melt the fat away are always bogus. And sometimes dangerous. Does anyone remember Ephedra

Limited scientific evidence or research

If someone is making a bold claim, they should be able to back it up with evidence. And I don’t mean their YouTube channel. 

They should be able to cite peer-reviewed scientific articles. And when they do, they should be taking in the entirety of that article and the rest of the scientific literature. And those studies should include humans.

This is a complicated matter, and scientific studies can be hard to read. I can’t tell you how many times I read an article about a study that describes the findings, only to read the study and the findings were misinterpreted, overstated, or certain aspects were cherry-picked to make their point while ignoring other factors.

On the other hand, if their only “evidence” is themselves or a couple of people willing to provide “testimonials,” you need to consider the possibility that they are not as credible as they want you to believe.

Claims to be a “miracle cure” for various health conditions

There is no food or supplement on the planet that will change your health single-handedly or miraculously. Food, lifestyle, environment, and genetics all work together to create our health outcomes.

Adding some unfamiliar berry or some super bitter and expensive vegetable won’t change a whole lot, even if you ate nothing but that food. 

Variety is an important part of a healthy diet, and eating one or two “superfoods” won’t harm you, but if you dwindle your diet to include only those “miracle” foods, you’ll be missing out on nutrients from a lot of other “ordinary” foods. 

Implies that food can change your body chemistry

This can come in the form of their diet pattern “boosting” your metabolism or increasing carb or fat “burn.” 

Sure, a true ketogenic diet can make you burn fat for energy. But so does fasting overnight.  It’s a natural process, and keto didn’t change anything, even if the claims state otherwise. (Also, your co-worker’s keto diet likely doesn’t put them in ketosis).

In addition, when on a ketogenic diet, you’re “burning” fat for energy because that’s what you’re eating, not because it’s accelerating fat loss.

Claims that their supplement, dietary additions, or dietary restrictions “turn on” a different metabolic process are bogus and should be regarded as the crap it is.

Suggests that your body needs a “detox” or “cleanse”

This is what your kidneys and liver are for.  And they’re remarkably good at their jobs. 

If your kidneys or your liver aren’t able to adequately remove waste or other undesirable byproducts of living, you have a medical condition needing a doctor. What you don’t need is a snake oil salesman on social media or another diet book.

The Potential Dangers of Fad Diets

So why do we care if something is a fad? This fad might be the one that works for you, right?

Unfortunately, it won’t. In addition to not working, these fad diets can be quite dangerous, leading to nutritional deficiencies, eating disorders, worsening physical and mental health, and more.

Nutritional Deficiencies

Nutritional deficiencies can happen for a variety of reasons.  If you are eating so much of a specific food, you tend to exclude other foods, leading to an imbalance of nutrients, even if you aren’t intentionally restricting otherwise. Take the negative calorie myth, for example.

There’s nothing inherently wrong with the foods that supposedly have negative calories. However, overeating these foods will lead to protein and fat deficits that can have serious effects. And that in addition to potential GI distress from a big jump in fiber intake.

Diets that severely restrict fat have the potential to lead to low protein intake as well.

Low-carb diets tend to lack fiber as well as many important vitamins, minerals, and phytochemicals.

Very low-calorie diets could lead to all the deficiencies. The more restrictive the diet, the more potential nutrient deficiencies there are.

Increased Risk of Disordered Eating Behaviors

Dieting is one of the biggest risk factors for developing an eating disorder.  Not a signal of vanity, eating disorders are serious mental health conditions, with anorexia nervosa considered the most lethal of all mental illnesses. And the effects are not limited to young girls.

The thing is, no one goes into a diet knowing that they will or even considering they might develop an eating disorder. They may start by thinking they are being healthy. Then they start to internalize the “ideal body” as a measure of their worth in society. 

Then someone says this is the thing that will help them achieve that. Then someone else says, “No, this is it.” And they keep on racking up dietary restrictions until food is something to be feared rather than a source of enjoyment and nourishment.

Adverse Effects on Metabolism

Even if your fad diet doesn’t devolve into an eating disorder, you will likely experience negative changes to your metabolic rate. While you can’t boost your metabolism necessarily, you can reduce it. 

Excessive calorie or nutrient restriction causes your body to conserve energy.  Adaptive thermogenesis is an effect that makes your body slow down its energy expenditure, reducing your metabolic rate and making you feel sluggish, fatigued, and full of brain fog. 

This is reparable, but it takes a concerted effort and help from a dietitian. 

Negative Impact on Mental Health

This is a huge topic, so we’ll just touch the very tip of it here. 

You need adequate protein, carbs, and vitamins to produce serotonin, melatonin, and dopamine. These are all affect your mood and behavior. 

When you don’t get enough of these nutrients, your body shunts what it does get to the most important functions, and a good mood just isn’t important compared to your heartbeat or your breath.

Additionally, various vitamins, minerals, and other compounds profoundly affect mental health when deficient in the diet, particularly magnesium, zinc, and the B vitamins. 

When you are restricting food, the diversity of your food tends to go down. Unfortunately, the diversity of our gut microbiome follows suit, and this can also lead to worsening mental health.

In fact, many people can link the onset of their anxiety or depression to an episode of food poisoning or antibiotic use, another way that microbiome diversity can shift drastically.

Low blood sugar, often a symptom of overeating and overexercising, can actually mimic panic or anxiety attacks in some people, creating a problem where there wouldn’t be otherwise.

They can be expensive

Even if the fad diet that’s currently being pitched doesn’t require the use of a bunch of supplements or other products (books, shakes, special kitchen equipment, or a membership), it can still place an unnecessary financial strain on an individual and their family. 

Because food is often demonized, many dieters throw away perfectly fine food that they’ve already spent money on. This can cause the person to double-buy groceries. Buying groceries once was likely expensive enough! 

Secondly, many diets encourage more elitist-type foods that may be more difficult than normal to find. This requires the dieter to not only buy more expensive foods than they may have otherwise but potentially drive to several grocery stores in order to find everything they “need.”

Examples of Fad Diets

There are so many predatory, fad, and dangerous diets out there, it would be virtually impossible to list them all. Fad diets can range from a few modifications to an unhealthy level of food and nutrient restriction. 

I’ve listed out some of the fad diets that I hear about the most or are some of the most dangerous. However, this is by no means anywhere near an exhaustive list. Unfortunately, if I attempted to list them all, it’d be out of date by the next day!

Look for patterns so you learn how to spot a fad diet.


The Atkin’s is probably my first real memory of a fad diet. I vaguely remember the low-fat craze of the 80s and some of the extremes in that realm (Olestra, anyone?), but Atkin’s was the first structured fad diet that I remember friends and/or family members trying.

Dr. Atkins wrote his book in the 70s, but for whatever reason, it came back into diet culture in the 90s.  This diet is a low-carbohydrate, high-protein diet. 

One of the biggest memories I have of people trying this diet was how grouchy they all were.  Turns out, there’s a reason for this, at it wasn’t because they missed dessert. 

As stated above, we use carbs to help produce our happy hormones, and all of a sudden, no one had any!

Atkins’ plan had an induction phase and a maintenance phase, though everyone seemed to stick with the strict first phase. This led people to create a diet pattern that was high in saturated fat and low in fiber, leading to worsening cholesterol and increased risk of colon cancer.

A modified version of Atkin’s is thought to help adults with epilepsy that doesn’t respond to medications.

The Cabbage Soup Diet

The Cabbage Soup Diet is almost exactly what it sounds like.  Cabbage soup, all day every day.  This is supposed to be a quick fix or a “jump start” plan that only lasts 7 days.  But my goodness, those 7 days are soul-sucking.

Essentially, you make a big batch of broth-based cabbage soup, essentially boiled cabbage +/- seasonings. No protein, no carbs.  You can have as much of this as you want. Then there’s a complicated list of “allowed foods” that are different every day for each of the 7 days.

And the allowed foods are weird, y’all. On day one, you are allowed all fruits except for bananas. But then on day 4, in addition to your soup, all you’re allowed is 4 bananas and a glass of skim milk…

Any weight loss on this diet is likely water and muscle mass loss due to the very low protein intake on this diet.  The number on your scale will return to normal, or be even higher, once the plan is finished and you can finally eat again!

Meanwhile, you’re likely feeling fatigued (but with difficulty sleeping), confused, and irritable, and have likely used up a lot of your stores of various vitamins and minerals. 


The keto craze over the last few years has been a nightmare.  I have never seen so many immediate and severe health complications from a popular diet.   

For what it’s worth, the ketogenic diet was originally created because some super-smart person learned that they can feed people with a specific ratio of fat to protein to mimic starvation while still allowing the patient to eat.

And why did we want to mimic starvation? Because some smart people before this guy found out that epileptic patients that were starving no longer had seizures. When this started to become a therapeutic tool for children with epilepsy, these young patients were put in the hospital under constant supervision with very strict menus.

Nowadays, most people on a keto diet don’t even achieve ketosis.  The fat burned during this diet isn’t because they are losing fat stores but because they are burning the fuel they are eating, fat. 

The keto diet has been extensively shown to lead to heart disease, colon cancer, worsening mental health, and fatty liver that can become liver cirrhosis if not addressed. Skip it.


Paleo’s an interesting one to me. The premise is terribly wrong. The claim that our ancestors didn’t eat certain foods so we shouldn’t either, has a few problems. 

For one, our Paleolithic ancestors only lived for about 35 years.

Second, archeological evidence proves that they ate many of the things paleo proponents say we should avoid. 

However, the diet itself isn’t horrible.  I’ve told people in the past if you HAVE to follow a fad diet, choose Paleo.  There is an emphasis on fruits, veggies, eggs, nuts, seeds, and lean meat.   All of this is good.  It limits excessive intake of sugar and salt. Also good.

However, there is no scientific basis for the elimination of legumes (beans, lentils, peanuts), whole grains, or starchy vegetables (corn, peas, jicama, potatoes). 

This diet is lower in carbs that I would feel good eating, but not insanely low, and there’s plenty of protein and healthy fats. Overall, not a terrible plan for you, healthwise, but it is expensive to maintain. Many of the foods that are eliminated on this plan are budget-friendly and healthy options.

Additionally, all of the rules can wreck your relationship with food and your ability to listen to what your body needs from you. 

Gluten Free

Gluten-free as a fad diet doesn’t have a ton of rules. Once you find “hidden” gluten, you’re pretty much ready to go. However, claims that gluten cause health problems are not founded in any research, and I’ve searched for it.   

There are some people that have a genuine need for a gluten-free diet.

Individuals with Celiac disease, a severe autoimmune condition, must avoid gluten-containing products for their entire life. There are also some other intolerances, where maybe someone can’t eat wheat products but aren’t quite so worried about cross-contact.

But for the vast majority of us, going gluten-free for our health or for weight loss doesn’t make sense. For starters, gluten-free alternatives tend to have more fat and salt than their traditional counterparts. They also tend to taste quite terrible. And they are insanely expensive, comparatively.

All of that, and you haven’t improved your health one bit.  Instead of eliminating gluten, try choosing whole grain options instead, and eat them as part of an overall meal rather than the star of the show.


  • The Military Diet – a 3-day diet that you repeat as many times as you want, with 4 days in between each cycle. This diet is essentially toast, tuna, hot dogs, a few specific fruits and vegetables, and vanilla ice cream. It is insanely low-calorie. Also, this is not actually associated with, or recommended by, the military.
  • Tapeworm Diet – Take a pill with a tapeworm egg in it. When it hatches, it eats all the calories for you. Seriously. This has been around in various iterations since at least the Victorian age.  And it can kill you.
  • Vegetarian/Vegan – I know, I know, but hear me out.  A well-balanced veg*n diet can be very health-promoting and doesn’t have to eliminate any nutrients. However, there is a subset of faddism to this diet, with some predatory people over-inflating health claims and making up claims of foods from animal sources. I once had someone try to convince me that milk is white because it’s full of pus! Not true, btw.
  • South Beach, Whole30, Dukan, Zone, Carb Cycling – all various iterations of low carb.
  • Raw Food Diet – No use of heat over 118 degrees.  This diet is low in protein, fat, and flavor. And horrendously hard on your gut.
  • Nutrisystem, Slim Fast, Optavia -buy our products and occasionally eat real food!
  • Cleanses – fruit juice cleanses, the Master Cleanse, and skinny (or diet, or detox) teas – just avoid all of them.
  • Carnivore Diet – all meat all the time; some proponents even advocate for raw meat.  Another hard pass.

Tips for Identifying and Avoiding Fad Diets

Stay vigilant; read and interact with a critical eye. If something makes you experience a visceral, emotional, or knee-jerk reaction, take some time to reflect. Put some space between you and the diet claims and come back when you’re feeling more rational. Then proceed as below. 

(side note: this doesn’t have to apply to fad diets or nutrition advice. Use the same tactic when evaluating political, policy, healthcare, or any other issue

Consult a Registered Dietitian or Healthcare Professional

I’m partial to dietitians, obviously, but for a reason. No other healthcare professional has the training we do. Just like I don’t have the training they do.

Dietitians get asked about fad diets all the time. So there’s a good chance that the RD you ask has already researched it. And if she hasn’t, she’ll have the resources to do so quickly. Preferably, speak to a professional that knows you and your medical history.

Look for Evidence-Based Recommendations and Research

If you have doubts about the nutrition plan you’re looking at, and don’t have a friendly dietitian to guide you personally, I would take some time to research credible sites for information. 

Look for sites that end in .edu or .gov.  You can also look for sites run by dietitians.  Healthline and US News tend to have good articles about nutrition and diets with a pretty good review process and cited sources.

Or, if you’d rather go straight to the source, PubMed is an excellent source for peer-reviewed, published research.

Avoid Diets with Extreme or Unsustainable Restrictions

If the nutrition plan you’re considering has you cutting out foods that are important to you or that you enjoy, it is not sustainable.

Likewise, if entire nutrient groups are drastically restricted, your body will do what it needs to in order to get the nutrients it needs. This means that you will be HANGRY. You will think about food constantly.

It’s not a willpower problem, it’s a fad diet problem

Use Common Sense and Critical Thinking when Evaluating Diet Claims

If there was ever a “perfect” nutrition plan that worked for everyone, was sustainable, and did everything a diet plan claims to do, everyone would do it. But instead, we see new claims, new pain points exploited, and new ways to make you feel like crap.

If something sounds to good to be true, examine it closer.


Fad diets are often characterized by unsustainable and extreme restrictions, rapid weight loss promises, and a lack of scientific evidence.

While they may seem tempting, following fad diets can lead to nutritional deficiencies, disordered eating behaviors, long-term weight gain, negative impact on mental health, and adverse effects on metabolism.

It’s important to prioritize your health and seek out evidence-based nutrition advice from registered dietitians and healthcare professionals.

Focus on making gradual lifestyle changes and following a balanced diet that includes all food groups in moderation. By doing so, you’ll not only achieve your health goals but also maintain them for life.

When using common sense and critical thinking to evaluate diet claims, you know how to spot a fad diet and make sustainable changes to your eating habits instead.

Remember, a healthy and balanced approach to eating is key to achieving long-term health and well-being.

What are 5 examples of a fad diet?

There are so many! The 5 most common I hear about currently are:
1. Keto Diet
2. Carnivore Diet
3. Juice Cleanses
4. Optavia
5. Paleo

What are two tips for identifying fad diets?

1. Think critically. Evaluate claims of miracles, knowledge no one else has, or assertations that go against the scientific consensus when you’re in a non-emotional state.
2. Look for a one size fits all approach. Protein, energy, and other needs all vary based on a ton of different factors. Anyone that spouts off the same number or uses the same calculation for everyone doesn’t know what they’re talking about.

What are some reasons to avoid fad diets?

*They aren’t sustainable, but when you can’t sustain them, you (or the creator) blame you.
* They can be very damaging to your metabolic health, generally causing muscle wasting.
* They can be very harmful to your mental health.
* Dieting is one of the major predictors of developing an eating disorder.
* They tend to cause deficiencies in various nutrients.

Why do people believe in fad diets?

Our society values thinness over a lot of other factors. Look in the media. If people in larger bodies are represented, they are the funny friend, are stupid, or are lazy, etc. People internalize that shit, judging both themselves and others based on the ridiculous stigma that thinness is associated with ALL THE GOOD.
So when someone comes along sounding authoritative and promising to make you thinner, it’s really hard not to get wrapped up in it. You believe this one will work because it HAS to work.
And they’re structured in a way that if you fail their fad diet, the problem is you, not the shitty diet, perpetuating the absurd idea that larger people have no self-control or are too stupid to stick to a plan.

Are fad diets successful?

What are you measuring here?

They’re successful at earning money for those peddling them. They’re successful in making you feel bad about yourself so you’re susceptible to their sales tactics. So for people in the diet industry, they are inexplicably successful.

For those that try the diets, they are not successful at weight management or at making you healthier or happier.

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