Is the “Fast Diet” Safe?

Small Diet MealSummer is coming – but how far would you go to slim down? It comes as no surprise that people are starving themselves to accomplish those goals – as evidenced by the growing popularity of the “Fast Diet” (also known as the 5:2 diet). This new fad diet has made its way here from the UK and is joining the ranks of other extreme diets.

The basis of the diet is intermittent fasting. You dedicate two fasting days during the week; on those two days, you are allotted only 500 calories if you’re a woman or 600 calories if you’re a man. You’re then allowed to eat what you’d like the other five days. Hence, the 5:2 diet. This diet would not be safe for those who are pregnant, breastfeeding, diabetic or have a history of eating disorders.

This concept was developed by a British physician, Michael Mosley, who tried the diet himself after reviewing studies about fasting and longevity. Many studies have shown the benefits of eating fewer calories – from reducing the risk of developing Alzheimer’s disease to having a longer lifespan.

However, there’s little research that specifically shows how effective or safe the Fast Diet actually is. After reviewing the research myself, I’m conflicted. Here’s why.

First of all, dieting by starving or extreme calorie restriction is never a good way to lose weight. You not only risk pushing your body in starvation mode, but your stressed body tends to crave sweets and starchy foods. This is also why I always recommend having a full breakfast every morning. Starving yourself just makes you hungrier for junk food later.

There are many other healthier diets that can help you lose weight in a safer way. You can also make simple lifestyle modifications that don’t have a “diet” label, which include not eating past 7 or 8 p.m., drinking more water, or sticking to a clean diet (choosing foods that have no preservatives, additives, or chemicals in the ingredient list).

With that said, I’m always interested in new ways of thinking about dieting, weight loss and wellness, especially in the face of our obesity epidemic. One Brazilian study published last month suggested that intermittent fasting has caused positive changes in blood sugar, fat loss and “an increased resistance to stress.”

More research is necessary to prove whether this diet is effective. It’s important to note that fasting for two days, and overeating, indulging, and making poor food choices the other five days of the week will not get you to your goals. You’ve got to be smart about what you’re eating all the time if you want to achieve results the right way.

In the meantime, read an excerpt from my book, YOU: On a Diet, which discusses simple, practical methods of dieting and how to avoid the most common dieting pitfalls from both a physiological and psychological perspective.