The kekwick diet works by forcing the body into a state of lipolysis, which occurs when there is a lack of glucose in the body causing the stored fat to be used and burnt. If there is a high enough amount of glucose in the body, then lipolysis cannot occur. Most carbohydrates and protein use glucose as there way of converting to energy so by eliminating these other food groups, leaving only fat in the diet forces the body into lipolysis. By consuming only 1000 calories a day, speeds up the process, as the body has to resort to converting stored fat to energy more urgently. 

This fat fast does require careful calorie counting as its important not to eat more than 1000 calories a day and to make sure that 75-90% come from fat. Many people find that eating smaller meals frequently helps to stop them from getting hungry. Instead of 3 meals a day, try eating 5 times a day, approximately 4 hours apart. Each meal should consist of 200 calories. Eating throughout a day and thanks to the high fat content you should not experience too much hunger. It may be strange eating at unusual times in the beginning but if you can stick with it for a few days you should get used to it. 

People whose metabolism is not extremely resilient should not try to do the fat fast, as it is not thought to se safe. People who are able to lose weight using other methods will lose weight to rapidly to be considered safe. For anyone who has struggled to lose weight using other methods, the fat fast carries very few health risks.