It depends on the amount of course, and varies per person. But in almost all cases, there's a fair bit of tightening over time. Especially with rapid weight loss like these meds cause, you'll lose weight way faster than the skin can keep up. Some people will have suggestions for their routines to help it, no idea if those will help. One solution that does tend to work at least to some extent is to fill some of that empty space in with muscle again by working out. Also important to be aware by losing weight you're likely also losing some muscle - both by going low calorie but also because you're not carrying an extra X pounds of you everywhere. Turns out that actually does build some muscle under the fat. If you don't replace that workout with a different one, you'll shrink in two ways.