Rapid Fat Loss crash diet by Lyle MacDonald’s , What is a crash diet and RFL in particular
In two parts we will deal with the famous Rapid Fat Loss (RFL) diet of Lyle MacDonald. Here we will clarify what it is and for whom it is recommended. In the second part we will look at things with a more practical focus and explain how the regime is composed and followed.
What is a “crash diet”? These are diets that aim to achieve maximum weight loss in the shortest possible time. They rely on a huge calorie deficit to cause the loss. Pay particular attention to the word “weight”. The big difference on the scales is in terms of body weight. This includes the loss of fat and water for the most part, but also of muscle and other tissues, as well as glycogen (the form in which carbohydrates are stored in muscle).
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What is a ” Rapid Fat Loss crash diet”?
These are diets that aim to achieve maximum weight loss in the shortest possible time. They rely on a huge calorie deficit to cause the loss. Pay particular attention to the word “weight”. The big difference on the scales is in terms of body weight. This includes the loss of fat and water for the most part, but also of muscle and other tissues, as well as glycogen (the form in which carbohydrates are stored in muscle).
What results can be expected? It depends. As you can guess, the indicators are huge. The results on the one hand will depend on how strictly the regime is followed. The stricter you follow the recommendations, the more significant the result will be. On the other hand, it depends on the body of the dieter. The heavier a person is, the greater the deficit and weight loss will be due to the very nature of calorie counting. The more obese the observer, the more fat will be lost.
An athlete with 10% fat and a weight of 80 kg carries 8 kg of fat. At the same time, an obese inactive person weighing 110 kg and 30% fat has 33 kg. It is obvious that people leaning towards the second group can lose much more weight. For diets that strictly limit carbohydrate intake, weight loss is greatest because the body, among other things, temporarily loses a large amount of water. In general, studies on extreme crash diets show a loss of 1-15 pounds (0.5-7.0 kg) in the first to second week, with average values around 7-10 pounds (3-4.5 kg).
The number also depends a lot on the calories you need to maintain your weight. If you maintain 2700 calories a day, then if you eat 800 calories a day, your deficit for two weeks will be 28,000 calories. That is, about 3.6 kg. On the other hand, an obese individual weighing 110 kg and supporting calories 3750 per day will create a deficit of 42,000, which corresponds to 5.4 kg. You have to take into account that the figures are valid only if there is no metabolic slowdown (increasing the efficiency of energy processes), which inevitably happens, and also if we assume that all the lost weight is fat. The above figures do not include the additional water loss that will occur.
In short, the RFL diet provides for weight loss in the range of 10-20 pounds (4.5-9 kg), of which 4-5 pounds (1.8-3.2 kg) of fat within two weeks.
When and for whom is such an approach appropriate? the Rapid Fat Loss Crash Diet
Before specifying for whom the diet is suitable, I will mention that a normal, not so aggressive and slower approach is always a better choice and largely healthier.
This is my opinion (editor’s note! – also to the editor!), And also to Lyle MacDonald, the author of the book. If you have already decided, here are the groups of people for whom the RFL diet is suitable:
- Competing bodybuilders. In general, competitive bodybuilding is a very extreme approach and extreme measures are never spared. In case the preparation does not go according to plan, less fat is lost than expected, there was something else that slowed down the process or the initial diet was not calculated well enough, then RFL can be useful. This is a way to catch up quickly with time.
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Athletes chasing category. This group includes wrestlers, boxers, powerlifters, Olympic athletes, marathoners and others. Sometimes you just need the weight to go below a certain figure.
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Upcoming special event. We all know what it’s all about – a ball, an anniversary, a surprise reservation by the sea, a ceremony, a wedding … etc.
- Launching a more moderate approach. For many people, the problem is that they start the diet, report slow results and interrupt it. Sometimes it is better to start extreme in order to see immediate quick and obvious results, which will give a serious motivation to follow a certain regime. RFL can be just the start of a moderate weight loss regimen. “Start with an advantage”, so to speak.
There are other cases, but these are the main groups.
Determining the percentage of body fat
In the second part of this material you will get acquainted with the specific details of the program, but in order to be able to determine your caloric intake, you need to know what percentage of your weight is fat. There is no way to know the figure with absolute accuracy, but it is not necessary. Approximate value also works.
People who have been involved in fitness or similar sports for a long time probably still have a good idea of where they end up. Others can find more information here. Caliper measurements are accurate enough for this purpose. The book also offers an easier version, but it can only be used by people who do not exercise, do not have extra muscle mass as a result of training and generally lead a sedentary life.
This is the use of the so-called body mass index BMI (Body Mass Index). To get it, you just need to divide your weight (in kg) by your height (in meters) squared. Approximately 90 kg and a height of 175 cm gives BMI = 90 / 1,752 = 29.4. It can be compared in a table to what percentage corresponds to the number. This is the most inaccurate option, so it is not recommended (3). The author offers it only for completeness.
Basic principles on which the Rapid Fat Loss Crash Diet is based
In the second part of the article you will learn how to create such a regime and how to calculate. Here we will only briefly explain some basic principles.
Protein
RFL is based primarily on protein. This macronutrient is essential for the human body, ie. without it, death occurs. Protein is the food with the most anti-catabolic effects. It will allow maximum preservation of muscle and organ tissue in the extremely low-calorie regime. It also causes the highest degree of satiety, which will help with strict adherence to the recommendations.
Lack of carbs
Carbohydrates are not essential. Our body can exist without them, therefore they are not needed during the regime.
Vegetables
They give great satiety and are a rich source of fiber. They are extremely important for hydration during the regime. The other very important thing is that they are rich in micronutrients – vitamins and minerals. Eating vegetables can protect against certain deficiencies.
Training
Weight training helps maintain muscle mass. There is also evidence that they have the ability to ensure adherence to a diet.
Sources used :
- BodyRecomposition.com
- The Rapid Fat Loss Handbook
- R. S. Ahima, M. A. Lazar. The Health Risk of Obesity–Better Metrics Imperative
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