The Fast Diet was published in January and has quickly become the go-to diet for all of Britain’s weight-loss hungry. According to authors Michael Mosley, M.D. and Mimi Spencer, you can eat whatever you want five days a week and lose 20 pounds. Who wouldn’t bite? For the other two days a week, you are limited to 500 calories a day. But still, sounds like the dream diet!
Only, nobody seems to acknowledge that during those 500-calorie days, you probably won’t be doing much of anything except sleeping. You’ll be light-headed, anxious, shaky, dizzy and super tired—imagine what you are like when you eat lunch late and multiply that by 100. You definitely shouldn’t drive, operate machinery, take care of young children, perform surgery or basically anything else that might put yourself and others at risk. You might pass out! And even if you don’t, your body doesn’t have enough energy (calories) to let your body function properly.
When you deprive yourself of calories or nutrients, you throw a wrench into the turning wheels of your cell processes and metabolism functions.
“The Fast Diet's premise of eating and drinking whatever you want for five days and then followed by two days of fasting may sound euphoric but it probably is not healthy for anyone; especially from an emotional and behavioral standpoint,” said Rose Green, R.D.
Further, these "fasters" are ignoring what it means to live a healthy lifestyle, which is being at peace with your activity level and creating a synergy between the way you think, feel and react to their food choices—on a daily basis; always; not just twice a week.
Green adds, “It is crucial for anyone serious about shedding excess pounds to develop a sensible eating lifestyle and to change one's self destructive eating habits. Fad diets like this one never will help you achieve permanent weight loss, since you really have not learned to create new healthy eating patterns.”
What’s worse: If you don’t consume enough calories over the five “eat whatever you want” days, the body may go into ketosis from lack of carbs (causing bad breath) or starvation mode, which is when the human body begins to slow metabolism and hoard fat. So while the British are kissing their water-weight goodbye with smelly breath, they run the risk of storing the fat they are so desperately trying to lose.
That’s not even counting all the unhealthy fats, carbs and calories the fasters must consume on their eat-whatever days. Let’s be honest here. Who chooses the salad with dressing on the side when they are at a buffet? Dr. Mosley was eating a cookie during his New York Times interview. What diet condones cookie eating?
Britain’s National Health Service isn’t buying into the trend so quickly either. They listed their warnings of negative side effects the same week the book came out.
Watch out America. Before you buy into the hype, believe the risks. If it’s too good to be true, it probably is.
A version of this story originally appeared on iVillage.