You may or may not be able to heal all the skin depending on how much weight you lost and how saggy your skin is now.
During any weight loss the important thing is to treat the skin every chance you get ; so, you don't end up with saggy skin that has no elasticity.
The techniques to employ (preferably as you are losing the weight) are these:
1. Every shower take a loofah or soft brush into the shower with you and give every inch of your skin a good brushing...a really good brushing. Don't rush, with this brushing you are removing dead skin and encouraging blood to enter the skin and nourish it. When you leave the shower, give yourself a good, rough drying with a non-softened towel. Then apply good healing oil such as Vitame E oil and massage into your skin. This will help your skin regain some elasticity.
2. If you are not showering or bathing that day, give yourself a dry brushing. Use your loofah to brush your skin (always towards the heart). Brush from your feet up to your waist and brush down from your head to the waist. Massage your oil in.
3. Change your diet to include 8 glasses of water in addition to everything else you drink. Eat as much raw food as you can (salad, veggie sticks, fruits, etc.) to provide good nutrition to the skin during these changes.
4. Add some raw honey to your diet. It is a powerhouse of good things.
5. Don't forget to exercise.
6. If it does end up that you require surgery to remove some of the extra skin, don't forget they accept skin donations to use for burn victims and many others.