First and foremost I recommend to go with the 500 calorie diet. However, if you are leading an active lifestyle, then you might be having trouble with low-calorie diet since you might be feeling hungry. At such instance, you can go for variations such as 800, 1200, and 1500 at your discretion.
However, bear in mind that it can extend the weight loss process. For instance, 20 lbs in 23 days might get extended to 20 lbs in say 40 or 45 days. I am just citing an example. Actual weight loss results may vary based on your bodily functions, calorie intake etc. Nevertheless, weight loss is guaranteed…!!!