What is the best exercise to loose weight?

Probably Running: An aerobic exercise program that works on cardiovascular conditioning [ key to metabolic changes from exercise] and expends a great deal of calories will be effective with weight loss. Swimming / biking will also work well. Maintaining muscle mass is also helpful.

Consistently: The best exercise, is the one you will do consistently over time. Its the one you enjoy doing and wont find as a chore. It can be as simple as walking with a friend on a regular basis. It has to be one that you are able to perform on a regularly, consistently, and with enjoyment so that you want to keep doing it.

Water weight, wait.: Scuba diving is one of highest calorie burning exercises you can do. It has to do with maintaining body temperature while being bathed in lower ambient water temperature.