Calorie value question.

You'll lose generally the same amount of fat either way, but you will be less healthy if you eat sweets instead of good foods, because you won't have vitamins and nutrition nourishing your body that it needs. Eating healthier (leaner, more protein, more veggies, etc.) will help your immune system, help your digestive system, help you retain muscle (or gain it if you are starting lifting), and your body will overall feel better and more energetic. On a diet of sweets, you might have trouble sleeping, recurring aches and pains, lethargy, depression, you'll be hungry more often because sugar makes you hungry, clammy skin, on and on. Imagine a tired, sickly looking person who weighs 160 lbs at 15% bodyfat, and then a healthy, glowing fit person who weighs 160 lbs at 15% bodyfat, and both eat the same amount of calories every day. It's because of their diet (and exercise), even though they lost (and now have) the same amount of fat due to calorie restriction.

To add on to what the others have said, you'll also be very unlikely to eat 1300 calories of only sweets and not be so hungry that you break your calorie goal. 1300 calories isn't a lot of food to begin with and to consume only sweets for any given period of time is going to be next to impossible. Most people will ultimately succumb to hunger in that example and overeat. When that happens you will begin to lose weight slower. If you somehow can maintain a diet of eating 1300 calories of only sweets you will as the others pointed out, lose weight at basically the same rate as eating a more variable diet of nutritious foods.