Could you tell me what's the best way, healthy low-cal diet and exercise aside, to lose weight quickly?

No short cuts.: Healthy diet and exercise. Best way to do it. Anything else is a gimmick and a short cut and unlikely to lead to meaningful permanent changes. Your diet does not necessarily need to be low-cal or low-fat. Investigate paleolithic and primal diets for some direction into more beneficial ways to eat than the low-fat high-carb diet pushed by the food pyramid.