Crash Diets & Why They Don’t Work

You’ve seen the headlines before: “Lose weight FAST!” “New low-calorie miracle diet cuts 10 pounds in 2 weeks!” These promises of dramatic weight loss have given hope to a lot of people who want to shed pounds in as little time as possible. And can you really blame them? 10 pounds in 2 weeks? That’s hard to ignore.

But these promises—these crash diets as they’re called—are just that: promises. Nothing more. Not only do they rarely work as planned, but they’re also not sustainable. They’re hard on your body, and their consequences can be unexpected and devastating.

Here’s a closer look at some of the most popular crash diets, what they do to your body, and why they don’t hold up as long-term weight loss strategies.

What Is a Crash Diet?

Also called a “fad diet,” a crash diet is an umbrella term for weight loss diets that keep calorie or carb intake low to help you lose a lot of weight in a short period of time. Most of them are just known by the foods that you’re supposed to eat while you’re on the diet: cabbage soup diet, egg diet, juice cleanse diet. (There’s also the tapeworm diet. I’ll let you draw your own conclusions about that one.).

What Are the Most Popular Crash Diets?

Rapid weight loss is the name of the game in crash dieting. Although each crash diet has its own small differences, the end goal is fundamentally the same: to lose weight quickly, no matter what.

Tempting? Yes. Dangerous? Also yes. Check out these popular crash diets and why you should pass on their promises of a quick fix.


Keto, or ketogenic, dieting has been all the rage for a few years now. As a high-fat, low-carb diet, it gets your body to switch its energy source from sugar (or glucose) to fat, specifically ketones, which your liver produces from fat. And when this happens, your body goes into ketosis.

Sounds simple enough. But the risks hardly make keto worth it. Along with nutrient deficiencies and the consumed levels of fat’s having been linked to heart disease, you’ll be risking constipation, kidney stones, and low blood sugar.

Carb cycling

Carb cycling involves alternating between high-carb days, low-carb days, and even no-carb days. It’s most popular among athletes, especially long-distance runners who want to keep their weight down while also getting enough carbs in for long runs or other intense workouts.

Unfortunately, many have started using carb cycling as a weight loss program, which it definitely isn’t. Over the long haul, any low-carb, high-fat weight loss strategy will increase your risk of insulin resistance, and carb cycling is no different. Unless you’re a world-class athlete looking to stay at a healthy weight while also wanting to load yourself down with carbs for an ultra-intense workout, then this just isn’t for you.


Also called phentermine, Adipex is a commonly-used pill that suppresses your appetite. It’s also usually prescribed for use up to twelve weeks. And because it’s a stimulant, it can also be addictive. Along with increasing your heart rate and raising your blood pressure, it can make you nervous and agitated.

Not only can you become physically and psychologically dependent on it if you use it long-term, but if you rely on it alone for weight loss even for twelve weeks, you’ll likely experience weight gain when you stop taking it. That’s because Adipex and other medicines like it require a lifestyle change—including a healthy diet and plenty of exercise—while you’re taking it and afterward to keep the pounds off.


The HCG diet combines a very low-calorie diet with daily injections of a pregnancy hormone called human chorionic gonadotropin (HCG). It also requires that you eat 500—yes, 500—calories or fewer per day, which is how you hear of HCG dieters losing five or more pounds per week.

I probably don’t need to tell you this, but losing weight on the HCG diet isn’t exactly a five-star idea. Not only are over-the-counter HCG weight loss medicines illegal1,  but limiting yourself to 500 or fewer calories a day could be fatal. Not to mention the potential side effects of mood changes, an irregular heartbeat, blood clots, and gallstones.

What Happens to Your Body When You Crash Diet?

As you can see, even the most popular crash diets are questionable at best for sustained weight loss. In fact, most of the weight that’s lost while on these diets is water weight and not actual fat. But overall, there’s no shortage of health consequences for crash diets if you’re on them for basically any period of time at all.

From slowing your metabolism and depriving your body of essential nutrients to weakening your immune system and causing heart palpitations, crash diets can do far more harm than good.

Exercise + Balanced Diet = Long-Term Weight Loss

Crash diets offer a temporary fix for losing weight. We know that. But over the long term, they can’t replace the only natural way to make it happen: the combination of exercise and a balanced diet. Here are some dieting tips for shedding those pounds and keeping them off the right way.

1. Focus on your behaviors, not just the numbers.

Weight loss can be intimidating for many reasons. One reason is facing the scale over and over again. To some, it can be like a wall that you keep hitting head-on. The numbers just stick with you, and you become so obsessed with them that it becomes a negative or fearful thing altogether.

But instead of focusing so much on the numbers, try focusing more on the behaviors that lead to good numbers. For example, instead of saying that you want to lose two pounds a week, try saying that you want to walk thirty minutes a day. This shift in perspective gives you small goals to hit and also puts your weight loss in more positive terms.

2. Be smart with your calories.

Not all calories are the same. You have good ones, and you have bad ones. The good ones are lean protein, whole grains, and healthy fats. The bad ones are processed foods, artificial ingredients, and unhealthy fats. And if you eat too much of the bad ones, you’ll only want more of them. Sneaky, I know.

So for long-term weight loss, you just have to be smart with your calories, and limit as much of the bad ones as you can. I’m not saying you have to turn down cake and ice cream at the birthday party. I’m not a monster. I’m just saying try not to go back for seconds or thirds.

3. Pick up those weights.

Lifting weights helps you burn more calories during the day, because it can increase your lean body mass. Yet it also helps you lose belly fat. When you lift weights and add more weight over time, your improved muscle mass will keep your metabolic rate up. In turn, this elevated rate burns more calories.

Sure, you might be sore after increasing the weight a bit. But that’s normal. As you do this, remember to drink a lot of water, and stretch before every workout. Keep it up, and you’ll be down a pants size or two in no time.

The Big Takeaway

Despite what many celebrity Instagram feeds say about losing ten pounds in two weeks, it’s almost certainly not the route you want to go for sustained weight loss. Not only does crash dieting come with its fair share of health risks, but it’s also unlikely to work as well as expected.

If you want to lose weight, you can’t beat regular exercise and healthy eating. You just can’t. There’s no substitute for that. And once you find this to be true for yourself, you’ll never look back.ν

1U.S. FOOD AND DRUG ADMIN., Avoid Dangerous HCG Diet Products, (July 13, 2020).