The 3 week diet is basically a combination of different diets which are chained together into different phases. The diet starts with a detox phase, then an optional fasting phase followed by two different low carb phases. br br As you might imagine with a diet promising such quick weight loss, the diet does seem quite extreme – and to carry out each phase to the maximum is not easy. As Karen found, it can make you feel pretty drained to start with. But as it’s only for 3 weeks and the final phase is the least daunting, it is achievable. It is possible to do the diet in a slightly less extreme form, simply knowing that you’re not maximizing your weight loss.