The new 'fast diet,' already popular in the UK and currently making its way into the United States, claims you can achieve your ideal weight while eating whatever you want for five days and fasting for two.

Medical journalists Michael Mosley and Mimi Spencer feature the details of this emerging diet trend in their book, The Fast Diet. Mosley suggests that those who employ the weight-loss technique can successfully lower their chance of heart disease by cutting cholesterol levels, improving insulin sensitivity, and losing more body fat, Reuters reported.

"The problem with standard diets is that you feel like you are constantly having to exercise restraint and that means you are thinking about food all the time, which becomes self-defeating. On this regime you are only really on a diet two days a week. It is also extremely flexible and simple," Mosley told Reuters.

Also referred to as the '5:2 diet,' the fast diet allows users to feast for five days and then limit themselves to 600 calories for each of the remaining two days. Calories can also be spread throughout the day to prevent hunger pangs.

"I either save all my calories for one meal at the end of the day, at around 5 p.m., or I have a very low-calorie meal at midday (usually homemade soup or a salad for around 150-200 calories) and the remainder of my calories for my evening meal," stated fast diet user Simeone Baker on the book's website.

"I try to avoid teas and coffees and stick to fruit tea and water. I exercise on Fast Days and actually enjoy my exercise more than on non-Fast Days!"

Since its announcement that the public should rethink the diet's health risks, Britain's National Health Service (NHS) has given no official word on the effectiveness of the 5:2 diet plan. When the diet regime originally gained ground, the NHS condemned it for possible side effects including difficulty sleeping, bad breath, anxiety, and mood swings.

However, a study conducted by the UK's University Hospital of South Manchester that analyzed the health effects of intermittent fasting in terms of cancer preventions forced the NHS to rethink its stance on the 5:2 diet's feasibility.

According to the study's findings, intermittent energy restriction (IER) and continuous energy restriction (CER) are both equally effective in curbing obesity and decreasing an individual's cardiovascular risk.

"In our study both IER and CER led to modest reductions in fasting serum insulin and improvements in insulin sensitivity which appeared greater in the IER group even 5 days after the 2 day VLCD," the research team stated.

"These parameters were predictably improved further during the 2 day VLCD, most likely linked to acute decreased levels of insulin and increased insulin receptor affinity with energy restriction."