Does the 5:2 Diet Really Work?

The person behind popularizing the 5:2 diet plan, Dr. Michael Mosley, is a medical journalist and an ardent follower of this diet. He claims to have lost nearly 20 pounds in a week after starting off with this diet.

The diet gained immense popularity after the documentary Eat, Fast & Live Longer featured on the BBC 2 television program Horizon. Along with writer Mimi Spencer, Mosley has provided a detailed overview of the diet plan and the science behind it in the book The Fast Diet: Lose Weight, Stay Healthy and Live Longer. In his book he explains how the diet works, the science behind it and the foods for the diet. He has drawn a lot of his theories from research on fasting by Dr Krista Varady in the United States and Dr Michelle Harvie in Britain. Before understanding whether the 5:2 works or not, it is important to take into account the science behind the diet.

Understanding the science behind intermittent fasting is the key to understanding how this diet really works. When we fast, the body derives energy from the glucose in the blood. Once the glucose in the blood is used up, the body takes it from the stored glucose also known as glycogen.

Once the glycogen reserves are used up by the body, the energy and glucose needed for everyday functioning is taken from the fat reserves. While this may make fasting look very attractive, but when done everyday it can push the body into starvation mode where instead of losing weight, the decreased calorie intake impacts the metabolism and results in muscle loss.

Therefore the 5:2 diet does not encourage starvation or severe calorie restriction, where the calorie intake is too less to lead a normal-healthy life. Instead the diet encourages eating "fewer calories" only on certain days. Although 500 to 600 calories is not much, you can get it from fiber-rich fruits, vegetables, grains. While proteins can be obtained from sources like eggs and lean meat. Oats porridge with cinnamon and nutmeg or a quinoa salad are some tasty yet healthy food options for this diet.

The following diet plan as suggested in the book for a woman (500 calories) includes:

Breakfast: 142 calories Half a tub cottage cheese 100 gOne sliced pear 100 gOne fresh fig 55 gDinner: 341 calories
Sashimi made with 3-5 pieces salmon 100 g and tuna 100 g served with soy sauce, wasabi and ginger.1 tangerine (mandarin)Total for the day: 483 calories
? Growth of New Brain Cells
The science behind the 5:2 diet is based on the feast and famine diet of early humans where there were days when these people would go without food. Mosley believed that this fasting led to the growth of new brain cells in the hippocampus due to the increased levels of protein called brain-derived neurotrophic factor, or BDNF. The hippocampus is the region of the brain that is responsible for memory. The new cell growth in the brain is further associated with memory improvement.

? Better Insulin Utilization
Apart from memory improvement, fasting and the excess of BDNF helps in mood improvement. It also helps the body utilize insulin better, by increasing insulin's effectiveness in storing glucose. This increased insulin sensitivity in turn reduces the risk of obesity, blood pressure, heart diseases and diabetes.

? Protection Against Cancer Cells
Fasting has also shown promise when it comes to fighting cancer. When the body has less food, normal cells go into a survival mode. Unlike cancer cells which keep multiplying rapidly, these healthy cells are forced into hibernation. This protects the cells from the cancer-causing cells, thus restricting the spread of cancer.

? Hard to Follow
Not everyone can follow this diet, and one of the many criticisms is that it is very hard-to-follow. 600 or 500 calories is not much and it can leave you very hungry and grumpy for the two days that you need to fast.

? Limited Evidence of Effectiveness
Hunger pangs are often accompanied by irritability, sleep problems, anxiety and dehydration. Moreover, there is insufficient scientific research on human subjects that can attest the actual weight loss with this diet. Critics of the diet say that intermittent fasting may give the digestive system a rest but there is no significant weight loss.

? Slows Metabolism
Nutrition experts believe that when the calorie intake is reduced on fasting days the internal body alarm is set off and it slows down the metabolism. Moreover, most people tend to overeat on the days that one is allowed to eat. Instead of cutting down the calories for two days, it is therefore advisable to reduce the daily calorie consumption to match the basal metabolic rate.

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