Losing 15 pounds in 45 days is ambitious but not unreasonable. A sustainable rate of weight loss is 1 to 2 pounds a week and, although losing 15 pounds in 45 days is a rate slightly higher than that, it is not so dramatic as to be unsustainable. One pound is equal to 3,500 calories, so to lose 1 pound you need to take in 3,500 fewer calories than you use. You can do this by eating less, working out more or a combination of the two.
Change your eating habits to reduce calories. Rather than eating less food, eat different food; have a cup of coffee with skim milk, for example, rather than a large specialty coffee with whipped cream on top. This lets you cut calories without feeling deprived.
Reduce your portion sizes. By eating just a little less at each meal, you can reduce your daily intake of calories.
Replace simple carbohydrates such as white bread with complex carbohydrates such as whole-grain bread and vegetables. Complex carbohydrates are less calorie-dense, so you can still fill yourself up but consume fewer calories.
Have a lean protein source with every meal. Examples include skinless chicken breasts, tuna and beans. These help you feel more full and therefore eat less.
Perform regular interval training, which is cardiovascular work that mixes high-intensity with low-intensity activity. For example, you can sprint on the long, straight sections of a track, then jog on the short curves. This burns more calories than exercising at a static rate and also boosts your metabolism, which means that your everyday activities burn more calories.
Speak with a personal trainer about a strength training program that uses compound lifts. These build your muscles and, like the interval training, make your metabolism more efficient.