You should follow the diet for a maximum of 12 weeks.  A break of 1-2 weeks is usually advised, during which you should increase your calorie intake and eat healthy or follow our maintenance plan. This follows the NICE (National Institute for Health and Care Excellence) guidelines for very low calorie diets. Don't worry though as this break can help you loose weight still if you follow the guidelines correctly and eat healthy. Short term increases in calories have been shown to improve weight lose through something described informally as the "whoosh effect"