Fasting diets have been around in some from for a long time now. The idea of a fasting diet is that you deprive your body of food for a certain amount of time. During this time your body will start to use the supplies of fat reserves up helping you lose weight. Often people refer to the 5:2 diet which allows for a reduced calories intake for 2 days and then eating regularly for five days. Over the last year or so, many people have found that this does not seem to be very effective for them as they need to either reduce their calories on the other 5 days too or swap and have reduced calories for 5 days and eat normally for two.
There are very mixed reviews on whether these sorts of diets are good for you or not, but they are proven to help with weight lost. If you are overweight and this is putting you at increased risk of other health issues then this form of dieting may actually help your overall health. If however you have other underlying medical issues or should not reduce your calories intake significantly for other reasons then this may not be suitable.