Fast is never healthy . . . so there are none that are "fast" and healthy.
A good diet plan is a change in lifestyle. Diets don't work if you're doing it just to lose weight then go back to the old ways of eating. You will gain it back and play yoyo dieting, which is also very, very unhealthy.
The best program, because it is about lifestyle change . . . for the rest of your life is Weight Watchers. It's is NOT a diet, it is learning about your health and being fit and trim. How to get there safely, sustain the loss once you're there and continue a healthy, trim lifestyle through life.
The only way it will work. Weight Watchers is available on-line, too. Should you attend the in-person meeting there's lots of support and encouragement and lots of learning about health, etc. In a fun way! I love it and have been very successful on it.
I have tried Jenny Craig (which I liked), Fit For Life, Anorexia (which almost killed me . . . literally) and others. Weight Watchers is the only one I have lost and kept off the weight and stayed healthy doing.