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Medically reviewed by Mary Ahern MS, RDN, RYT February 24, 2025| Written by Zenda Nel

What Are FAD diets and Do they Actually Work?

A fad diet is something that many people have tried at least once. A fad diet is a trendy eating plan that appears out of the blue and attracts many followers for a short time. They seem to have ‘solid scientific backing’ and often make unrealistic claims about quick weight loss or health benefits. But in reality, there is no objective scientific proof. 

In essence, fad diets are like attempting to assemble furniture without instructions—promising at first, but often leading to frustration and mixed results. 

Yet, they remain popular. In a world where obesity has taken on epidemic proportions, fad diets are garnering hordes of fans. From eating 16 jars of baby food a day, or just ice all day long, to wearing blue-tinted glasses at every meal, fad diets are either extreme or severely restrictive. 

What is their allure? They all promise a quick fix to those extra pounds. And after all, some or other celebrity swears by it, so it must work.  

The fact is, these diets might work for some people but typically not long term. If one of them were successful, there would be no need for a new diet every few weeks. Stands to reason, doesn't it?

When is a Diet Healthy and When is it a Fad Diet? 

Scientists make the distinction based on the followingcharacteristics of fad diets:

  • Promise rapid weight loss
  • No attention is given to the necessity to be physically active
  • Focus on short-term gains rather than lifelong sustainable lifestyle goals
  • Give preference to one type of food or exclude an entire food group
  • Is unsustainable in the long term
  • Provides doubtful nutritional value 
  • Doesn't warn those with chronic diseases of possible health consequences
  • Lacks a scientific basis for the diet and its claims

10 FAD Diets: Their Quirks, Claim to Fame, and Why They Don't Work!

1. Keto Diet – You Are Seriously Missing Out!

Many people think of the keto diet as a high-protein diet but it's actually a high-fat diet. In fact, the diet is 75% fat, 20% protein, and 5% carbs. Yes, you read that right: only 5% carbs per day. So, no or very little bread, pasta, rice, or pizza. Who can stick to that? 

That means other carbs (and important sources of the incredibly beneficial nutrient, fiber) like legumes, grains, most fruit, some vegetables, fruit juice, honey, and soda drinks are also forbidden. 

As far as weight loss is concerned, you may achieve your goal in the short term, but the chances that you would be able to stick to such a restrictive diet are slim.

Health-wise, it's not a good diet according to research. Scientific evidence shows that the keto diet leads tomicronutrient deficiencies and provides too little fiber, which has a detrimental effect on the intestinal microbiome.

2. Blood Type Diet – What Are You Thinking? 

From what I have observed, many people are fascinated by the idea of eating according to one's blood type. The topic frequently comes up in conversation and I am always told, you can't be a vegetarian with an O blood type, you should eat meat! No, thanks.

Briefly, the diet works like this.

  • O Blood Type Diet – on this high-protein diet, the best foods are meat, poultry, fish, fruits, and vegetables, but not so much grains, beans, and dairy.

  • A Blood Type Diet – this is mainly a vegetarian diet with vegetables, fruit, whole grains, legumes, tofu, nuts, and seeds. This diet minimizes meat and dairy.

  • B Blood Type Diet – this diet allows a variety of foods, including meat, seafood, fruit, vegetables, grains, and dairy, and excludes random food items like lentils, corn, chicken, and soy.

  • AB Blood Type Diet – this diet includes foods from the type A and type B diets, including meat, dairy, tofu, fruits, and green vegetables.

All four dietsexclude certain food types. 

Since the blood type diet promotes lean meats, fiber, fruits, and vegetables, and eliminates added sugar, it helps with weight loss, but that's because these are mostly healthy diets, and research evidence shows it hasnothing to do with blood type.

3. Detox Diets – Don't Insult Your Liver!

Detox diets, also known as cleanses, can be as strict as fasting for days, only allowing some liquids, using enemas and laxatives to clean out the colon, or only eating certain foods. The regimen lasts for a short time and is usually followed by a strict diet of raw vegetables, fruit, fruit juices, and other liquids.

The premise is that this"cleanses" the body of toxins. 

This premise holds no water. Why? Because our bodies are great at getting rid of toxins:

  • The lungs exhale carbon dioxide.
  • The large intestine gets rid of what our bodies don't use.
  • The liver processes help the body to eliminate harmful substances.
  • The kidneys filter blood and produce urine to help flush byproducts of digestion and other processes from the body.

Because of the severely restricted calorie intake, you'll lose weight but it's unlikely you'd be able to keep it off since these diets are not sustainable. Once you start eating normally again, the weight rushes back on. 

In addition, cleanses such as colonic irrigation or colonic hydrotherapy canharm the large intestine.

4. Raw Food Diet – Resign yourself to missing out on heartening stews and soups in winter

Proponents of this diet, who only eat uncooked plant-based foods, believe that raw foods are more nutritious than cooked food. According to their thinking, cooked food is less nutritious because of nutrient loss during heating. 

There is no denying the diet has some distinct benefits. A raw food diet includes uncooked fruits, vegetables, and nuts and can include milk, all of which are highly nutritious. Being low in calories and high in fiber, this diet tends to lead to weight loss.

Besides, heating makes some foods like milk safer and can release the beta-carotene from raw vegetables like carrots, making them more nutritious when cooked. In fact, heating food is what makes most meat proteins available to humans and easy to digest, which is important.

5. Paleo Diet – Retreating to the Dark Ages

The Paleo diet, also known as the"caveman diet", focuses on foods presumed to have been available to early humans. It is presumed that early men were hunter-gatherers, so they ate foods they could find or hunt such as meat, fish, plants, fruits, nuts, and seeds. The diet excludes grains, legumes, dairy, refined sugars, and processed foods.

You can lose weight on the Paleo diet since it's high in protein and low in carbohydrates. Presumably, the foods were high in fiber and protein, which contributes to a full feeling and prevents overeating. 

However, results may vary depending on how a person interprets the diet, as there are no clear guidelines. Also, the diet restricts entire food groups like whole grains and dairy, which could lead to nutrient deficiency. Depending on how the diet is interpreted, it can be high in animal fats, leading tohigher cholesterol levels

Besides, do we really know what people ate tens of thousands of years ago?

6. Atkins Diet – Don't Start It; It's Too Hard to Stick To!

The Atkins diet is one of the original fad diets. People have been following it since the 1970s. The diet is famous for severely restricting carbs. 

It certainly works if you want to lose weight, I can attest to that. I can also attest to not being able to stick to it, which is a common problem with fad diets.

The Atkins diet restricts carbs and encourages eating protein and fats. Carbs are, in fact, our main energy source and a macronutrient that our bodies need. 

Research shows that low-carb, high-protein (LCHP) diets put people at risk ofmetabolic imbalances and chronic kidney disease. The scientists also note that people struggle to stay on the diet.

7. Grapefruit Diet – No, Grapefruit is Tasty, Not Magic!

The Grapefruit Diet has been around since the 1930s. It involves eating grapefruit or drinking grapefruit juice with every meal. The diet limits daily caloric intake to around 800–1,200 calories and allows high-protein foods like eggs, meat, and fish but restricts carbs and sugar. The diet has several variations.

The grapefruit diet is based on the idea that grapefruit contains fat-burning enzymes and the promise is that you can lose 10 pounds in 12 days.

The different versions of the grapefruit diet are low in carbohydrates and calories but high in protein. So, these types of diets can result in weight loss with or without the inclusion of grapefruit. The weight loss is more likely to be the result of the low calorie and low carb content of the diet and not the fat-burning enzymes. There is currentlyno scientific research that supports the claim that grapefruit has fat-burning enzymes that increase fat-burning metabolism. 

The grapefruit diet has one specific health risk. It interferes with certain drugs, so if you want to try it, speak to your doctor first.

The grapefruit diet may lead to short-term weight loss, but it's not a sustainable option for long-term weight loss and may lead to fatigue due to the limited calories, especially if you do the diet for almost two weeks.

8. Cabbage Soup Diet – Think About the Potential for Unpleasant Odors!

The cabbage soup diet revolves around copious amounts of cabbage soup with every meal. Other low-calorie foods, such as fruit, vegetables, and a little protein are gradually added on different days there are alternate versions of these additions.

The diet typically lasts for seven days and promises rapid weight loss.

There areno scientific studies about the ability of cabbage soup to aid weight loss. The diet may result in quick weight loss due to its very low-calorie intake, however, most of the weight loss is water weight, not fat, and the results are rarely sustainable.

Such a restrictive eating pattern is bound to be poor in essential nutrients, such as healthy fats, protein, and a variety of vitamins and minerals, so it should be followed for a short period only. 

Besides, cabbage is notorious for causing digestive discomfort like bloating, gas, etc. Maybe a normal, calorie-restrictive diet would be more agreeable for everyone.  

9. Whole30 – a 30-Day Promise is Too Good to be True!

This is an elimination diet that excludes sugar, processed foods, alcohol, grains, legumes, and dairy. After 30 days, foods are gradually reintroduced to identify sensitivities. The diet's claim to fame is that it resets eating habits, helps with weight loss, identifies food sensitivities, and eliminates food cravings. 

It could have been a healthy diet because it eliminates foods that should be limited like added sugar, processed foods, and alcohol. But also eliminates healthy foods like grains, legumes, and dairy.

The very promise that this diet will reset your relationship with food and that after 30 days you won't miss any of the prohibited foods you used to love is a clear indication that this is a fad diet with short-term promises and no long-lasting benefits as confirmed by its ranking as the worst diet by the U.S. News & World Report in 2017 as reported bythe Independent.

10. Low-Fat Diet – Surprise, Surprise!

For decades, our TV screens, websites, magazines, textbooks, doctors, and even food labels were promoting low- or no-fat everything. Full-fat anything was public enemy number one. And what do we sit with today? More people who are overweight. And now we are told that's because low-fat foods are made more palatable through additives. In fact, the low-fat or fat-free versions of foods havejust as many or more calories as the full-fat versions of the same foods.

The low-fat craze is now recognized asa failed experiment that was not based on sound science, with health experts saying that it failed because itexcluded all fats, including healthy fats. In ascientific review, low-fat diets are discussed alongside other fad diets. 

Despite the public recognition by the scientific society that the thinking behind the low-fat diet was flawed and that all fats are not public enemy number one, the idea persists in the public consciousness, with people continuing to opt for low-fat options. 

Conclusion

Fad diets are short-lived wonders with no real lasting health benefits. They are usually hard to stick to and don't deliver on their promises which are not based on sound principles.

It's more rewarding to follow ahealthy eating plan you can stick to and that provides all the nutrients you need, including fiber.