You can absolutely do the master cleanse for 10 days. You should keep exercise to a minimum during the fast. Stop if illness occurs or you feel exhausted of course. Although weight-loss occurs during fasting it is not a long term solution to weight loss. Most cleanses achieve the 1 lb a day weight loss depending on water weight lost. Juice fasting is another route to go. You should consider a dietary program such as a low fat high raw vegan diet for sustainable fat loss. Hope this answers your question!