Crash Diets, Meal Skipping and Starvation: Why They Don't Work

In today’s society there is a lot of pressure to be thin. Thinness is associated with success and beauty, and some people go to extreme lengths to achieve this ‘ideal’ body type. However crash dieting, severe calorie restriction and meal skipping do not contribute to permanent weight control and can be dangerous.

When you starve your body – and this doesn’t just mean not eating altogether, it could be cutting out food groups or skipping meals – it enters crisis mode and does everything it can to survive. When calories drop to below your body’s basic requirements, it perceives danger in the form of starvation and its survival mechanisms kick in. Firstly your metabolism will slow down as your body tries to preserve energy until the famine is over; fat stores will remain and only emergency energy supplies will be used to perform bodily functions. This emergency energy comes in the form of glycogen, a necessary molecule produced as a result of excess glucose (sugar), which is stored primarily in your liver and muscle tissues and then as fat. Glycogen is linked to four times its weight in water, so every time your body uses glycogen for energy you will lose fluid and muscle tissue. If you’ve heard people talking about miracle diets in which they’ve lost 10lb in a week, what they’ve actually done is put their body through stress by severely restricting calories and therefore triggering danger signals within their body, causing it to utilise stored energy and lose weight in fluid and muscle mass – they have not lost much, if any, fat at all.

As your metabolism slows down your body will work below its optimum level in an attempt to save energy. You will find yourself suffering from mood swings, tiredness, insomnia, irritability and sluggish digestion because your body is focusing on keeping your heart beating and your lungs expanding and contracting: its sole aim is to keep you alive. A slow metabolism will result in the calories that you do consume being stored as energy, in fat or as glycogen, meaning you won’t lose weight, you are actually more likely to gain weight. Therefore it is vital that you eat regularly and don’t skip meals in order to keep your metabolic rate steady so that you keep burning the calories as fuel.

If your body perceives a famine because you’re severely restricting calories or skipping meals altogether, you may find yourself becoming preoccupied with thoughts of food. Cravings for sugary, fatty foods will dominate and before long you could find yourself bingeing on biscuits or eating a whole pizza. This does not reflect a lack of willpower but instead it is a signal from your body that it needs fuel. When our ancestors were hunter-gatherers they would regularly face periods without food and so when food became available they would eat lots of it in order for their body to store excess energy as fat. Then when the next famine came, that fat would be used as energy until food was available again. However today that famine never comes so the excess fat many people have stored never gets burnt, but we have not lost that instinctive drive to overeat when our bodies believe we are starving. This leads to a dangerous cycle of yo-yo dieting, bingeing and starving and constantly feeling guilty about ‘falling off the wagon’.

Most crash diets have one thing in common: a severe lack of carbohydrates. The Atkins Diet is probably the most well-known anti-carbohydrate diet but it comes with a string of negative side effects. A massive reduction in carbohydrates will result in rapid weight loss, but as I’ve previously mentioned this is not fat loss but vital fluids and muscle tissue being lost. Carbohydrates are in fact the body’s most basic and efficient source of energy; natural sugars (such as those found in fruits, vegetables and whole grains) are converted into glycogen which is then converted into glucose and used as fuel. However when carbohydrates are restricted or completely cut out from the diet, there are no natural sugars to convert into glycogen, and no glycogen to convert into glucose – so where is your body going to find the glycogen it needs? Initially glycogen will be extracted from fat but before long it will be taken from muscles, meaning you are not losing fat. Therefore the success of low carbohydrate diets (or rather, the reason why so many people lose weight on these diets) is actually down to muscle and fluid loss once again.

Side effects of crash diets, namely low-carbohydrate diets, can be very unpleasant and mimic the symptoms of diabetes. Hypoglycaemia (low blood sugar) and ketosis (excess blood ketone levels) will lead to light headedness, fatigue, nausea and bad breath as well as constipation as a result of a lack of fibre. Remaining on a low carbohydrate diet for a prolonged period of time can have very serious consequences; one recognised cause of bowel and colon cancers is a lack of fibre in the diet.

Complex carbohydrates are so essential that they actually have advantages to being in your diet. Firstly, you are less likely to gain weight in the form of fat if you eat carbohydrates. This is because the process in which carbohydrates are converted into fat consumes a lot of calories itself. Secondly, eating complex carbohydrates can actually increase your metabolism. This is due to two hormones being released as the carbohydrates are being broken down into sugars and insulin is released. These hormones - noradrenaline and thyroxin - increase the metabolic rate, allowing your body to effectively burn calories.

So if you’ve been successful and lost some weight on a crash diet, or as a result of starving your body of calories, is it possible to keep the weight off? The answer is no. When you return to your normal eating habits, your body won’t just ‘snap’ back to into its ability to function efficiently. You will have slowed down your metabolism, meaning your body will want to preserve every bit of energy it can get, resulting in you putting the weight back on. Often you will actually put on more weight than when you started. The constant hunger, bingeing, guilt and starving experienced during crash diets, starvation, calorie and portion restricting and meal skipping do more damage than good and will never result in maintaining a healthy weight or controlling your weight in the long-term. Your body needs a balanced diet which includes proteins, complex carbohydrates and fats at every meal, eaten regularly throughout the day so that the metabolic rate stays constant and your body can function properly whilst losing weight steadily. This is the simplest, easiest and most effective way of controlling your weight in the long-term.