Be aware: this is only the goal of this diet, not necessarily its outcome. Results vary from person to person. Consult your doctor or dietician before starting this (or any other) diet.
A crash diet is a diet in which you consume very few calories a day. Its goal is to lose a lot of weight in a short period of time.
On the homepage you can compare this diet to other diets.
An official definition of the crash diet doesn’t really exist. However, we can give a good description. It’s a diet that focusses on eating much less calories than your daily caloric need.
On average men need about 2500 kcal, and women about 2000 kcal a day. You can read more on this on the calorie counting page.
This number represents the average caloric need per day. It is also possible to look at the basic caloric need: the Basal Metabolic Rate (BMR). This is the number of calories you need per day if you would nothing but lying down all day.
Usually, a crash diet has a lower caloric intake than the BMR.
You can use this site to calculate your BMR. It is important to note however, that your body can differ from the standards used in this calculation.
It is not clear what makes a diet a crash diet. Sometimes a diet that has a maximum of 800 kcal a day is considered a crash diet, whereas other sites/sources state that a crash diet is any diet that has a maximum of 1400 kcal or lower a day, like the 1200 kcal diet of the 1000 kcal diet.
An important factor here is that people differ in their daily needs, because their bodies aren’t the same. A 1400 kcal diet can therefore be a crash diet for a bigger person, whereas 1400 kcal can be enough for a small person.
A crash diet focusses on short term weight loss. It is important to be aware that, when on a crash diet, most ‘fast’ weight loss isn’t body fat, but water and glycogen.
Glycogen is a form of sugar that is stored in your muscles and in your liver. It provides a ‘fast’ energy source that is used first if your calorie intake is too low. According to the Dutch Diabetic fund, your muscles can store 300-400 grams of glycogen. If you burn part, or all, of your glycogen, your body will restore this as fast as possible.
Same goes for water. If your calorie intake is too low, the amount of water you retain can be reduced, indicating weight loss. This can, on average, be 1 to 4 kilograms of water.
More on these and other factors in weight loss that should be accounted for can be read on this page.
Besides breaking down glycogen and losing water a crash diet can also lead to nutrient shortages. It is therefore very important to discuss following the diet with your (house) doctor or a dietician.
Additionally, a crash diet can initiate muscle breakdown. Muscles require much energy. When you lower your daily calorie intake for a longer period, the body can start to break down muscles to reduce the energy needed to maintain these muscles. The body adapts to the new caloric intake.
This also has consequences when you stop following the crash diet and start increasing the number of calories you consume per day. Since your body requires less calories (because it has adapted to the crash diet), you will gain weight easier when returning to the eating habits you had before starting the crash diet.
Finally, it is good to realise that your body wants to compensate for all the calories it has missed out on while you were on the crash diet. You will feel the need to eat more after finishing the diet.
As you might know, there are many different crash diets available. And because doing a crash diet is hard, there are also many strategies to lower the amount of calories you consume.
Below, we describe 6 different strategies with some examples of crash diets that use the mentioned strategy.
This first strategy is the simplest strategy. You count the calories of all the products you use and as soon as you hit the maximum number of calories allowed, you stop consuming products that contain calories. Examples of such diets are the 1000 calorie diet, the Dr. Nowzaradan diet and the 1200 calorie diet.
Within this strategy, an alternative to counting calories is provided by the points diet. Instead of counting the number of calories the products contain, you count the number of points given to different products. This comes down to the same thing, but can be easier to count.
Some crash diets focus on just one product. This is the main (or only) product you can use throughout the diet. These diets are called mono diets.
Limiting the diet to just one product makes calorie counting a lot easier. There is also no need to think about what you can and cannot eat. It might be a lot harder to stick with this strategy however.
An example of the diet that focusses on two products is the potato and yoghurt diet.
There are crash diets that are sold under a certain brand. These products have a set number of calories to make it easier to track them.
This strategy is much like strategy 3. The difference is that you do no use products of just one brand. You can follow pre-set menus that already have a known amount of calories. This makes it easier to count.
Another strategy to lower the number of calories you consume is to skip entire meals. For instance, you skip breakfast and by doing so you fast between diner and lunch. Read more on intermitted fasting on this page.
The Fast 800 is an example of a crash diet that uses such a strategy. This diet has a number of days in the week on which you fast and strongly reduce the number of calories. This strategy is also used by the 5:2 diet.
The final strategy here is the exclusion of product categories. This category can be carbs, for instance and an example of a crash diet that excludes these is the 17 day diet. In this diet you limit the amount of calories to max. 1200 kcal and focus on consuming products that contain fats and proteins, but no (or very little) carbs.
Diets and crash diets are widely discussed topics, including in various podcasts. An example of such a podcast is Crash Diets, After-life or Aftermath? with Anthony Bainbridge (ad link), an episode of Stronger U, which can be listened to below:
Do not just start following a crash diet (or any other diet). Consult your dietician or doctor first. Additionally, if you are overweight, please contact your dietician or doctor.
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