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Amy Berger
Jan 4  ·  4 min read
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What is a crash diet and why is it bad? What is a fad diet?

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If you’ve been following a low-carb or keto diet for a while (or if you’ve thought about trying it), chances are a friend or family member has expressed concern about you doing a crash diet or following a crazy fad. Are these concerns valid? Are crash diets bad, and if so, is keto a crash diet or fad diet?

What is a crash diet?

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There isn’t a formal, academic definition of a “crash diet,” but when most of us hear that phrase, we think of something extreme and potentially dangerous that’s meant to get big results very quickly—with “results” typically meaning weight loss. Crash diets often involve severe calorie restriction and may also recommend consuming specific amounts of a very limited selection of food.

They may also call for various concoctions and special supplements intended to help your body “detox,” “cleanse,” or boost the function of your liver, kidneys, and other organs that are already doing this for you 24/7. Crash diets aren’t meant to be followed for the long term, mostly because they’re unrealistic and they’re not safe as a permanent way of eating. 

Why are crash diets bad?

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It’s easy to understand why people are drawn to crash diets. Why wouldn’t we be enticed by attention-grabbing headlines and impressive before & after pics promising that we can drop pounds seemingly overnight

The problem is, even if these strategies work, they work only for as long as you can stick to them—which isn’t long! Typically what happens is the weight comes back on just as quickly as it came off. If you’re desperate to drop a few pounds of water weight and feel less bloated before a class reunion, family wedding, or some other special event, a crash diet might help you do that but it won’t solve any weight problems for the long term.

Doing things this way doesn’t teach you how to eat in a way that you can maintain and enjoy long term.

What is a fad? Is keto a fad diet?

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Compared to a “crash diet,” it’s easier to find definitions for what a fad is. An online dictionary defines a fad as “an intense but short-lived fashion; craze.”

By these definitions, keto diets aren’t a fad at all. Quite the opposite, in fact. Medical doctors as far back as the 1790s recognized that diets consisting almost entirely of fatty animal foods with little to no vegetables could improve diabetes.

A few decades later, in 1825, the famous gastronomic writer J.A. Brillat-Savarin wrote The Physiology of Taste, now a classic text in the culinary world. It was known even then that overconsumption of carbohydrates was a major driver of excess body weight.

Brillat-Savarin wrote, “…the principal cause of any fatty corpulence is always a diet overloaded with starchy and farinaceous elements,” and, “A more or less rigid abstinence from everything that is starchy or floury will lead to the lessening of weight.”

So with keto being around for more than two hundred years, it can hardly be called a fad. A bit more recently, the Journal of the American Medical Association published an article in 1957 recommending a nearly zero-carbohydrate diet to treat obesity: “The simplest to prepare and most easily obtainable high-protein, high-fat, low-carbohydrate diet, and the one that will produce the most rapid loss of weight without hunger, weakness, lethargy, or constipation, is made up of meat, fat, and water.”

The following year, Dr. Richard Mackarness published a book called Eat Fat and Grow Slim, which called for a very low-carb diet consisting mainly of proteins, fat, and non-starchy vegetables.

Then in 1960, Dr. John Yudkin published articles in the prestigious medical journal The Lancet on diets made up primarily of protein and fat for the purpose of weight loss.

Then in 1972 came arguably the most influential low-carb/keto book of the modern era—probably of all time: Dr. Atkins’ Diet Revolution. (1972 was a big year in low-carb publishing, as the same year saw the release of Pure, White, and Deadly, a book in which Dr. Yudkin warned people about the dangers of a diet high in sugar and refined carbs.) 

So, if low-carb and keto diets are a “fad,” they’re a fad that’s been around for over two centuries. (Take that, mood rings and bellbottoms!) 

Is keto a crash diet? 

woman sitting at table

Keto doesn’t fit the description of a crash diet. Most approaches to keto encourage consumption of protein and fat to satiety. Unlike crash diets, that means you’re allowed to eat until you’re satisfied or comfortably full. You don’t need to deliberately restrict calories or force yourself to go hungry. You can eat—just keep the carbs low!

This makes keto different from crash diets that put strict limits on how much you can eat. (If you’re struggling with weight loss, though, you might need to be careful with added fats and oils. Keto isn’t a license to stuff yourself at every meal, and you don’t need to deliberately load up on extra fats in order to reach any particular fat macro.) 

Another thing that sets keto apart from fads and crash diets is that it’s scientifically sound. It’s based in human physiology and biochemistry, not snake oil and empty promises. By centering the diet on protein and fat, you’ll get the full complement of amino acids and essential fatty acids, plus the critical vitamins and minerals that come along with them. You can eat a wide array of food from both plants and animals.

The only things you need to avoid are foods high in sugar or starch. 

It’s hard to see how anyone could think eating liberal amounts of beef, poultry, pork, lamb, seafood, game meats, dairy foods, non-starchy vegetables, nuts, seeds, and small amounts of fruit, is a crash diet or a fad. 

Another definition of fad is, “A temporary fashion, notion, manner of conduct, etc., especially one followed enthusiastically by a group.”

We’ve already established that keto isn’t temporary, but it’s true that this way of eating is followed enthusiastically by a group—a group that wants to lose weight and keep it off for good! (Not to mention reverse type 2 diabetes, metabolic syndrome, PCOS, acid reflux (GERD)non-alcoholic fatty liver disease, and more.) Knowing you could get results like that, why wouldn’t people be enthusiastic?  

Summing up

group eating at table

Keto isn’t a fad or a crash diet. It’s a way of eating that supports healthy blood sugar and insulin levels, and that can help improve or reverse a long list of issues that result when glucose and insulin are chronically high. You don’t have to suffer through intense hunger or extreme deprivation.

Keto diets let you choose from a wide array of different foods and nourish yourself well for long term health.