Depends on timing. If 6-8weeks or more away, strict diet and daily exercise can do this. Best diet for rapid weight loss is a low-carb diet. Exercise should alternate between aerobic and weight training. Keep up the diet and exercise afterwards to keep from re-gaining the weight, as yo-yo'ing is worse for health than steady high weight. If less than 6 weeks away, there really is no healthy way to do this.
At a moderate pace. Eat healthfully. Try to eat at least 5 servings of vegetables & 4 of fruit per day. Increase nutritional fiber. Avoid refined sugar & junk carbohydrates. Avoid alcohol, sweetened juices, soda & caffeinated beverages. Aim for 7.5 to 8 hrs of sleep / night. Hydrate w at least 64 oz of water / day. Calories burned must > calories consumed. Do both cardio & weight training.
Adrenals + detox. Reset your adrenals with adhs (vasopressin) will be able to loose 6-8 pounds per month combine that with detox of colon, liver and lymphatics you can achieve your 15 pound goal. Learn how to do ionithermie this targets the specific areas like belly, underarm, and inner thigh areas.