Strategies To Lose Weight Fast

I need to lose weight but afraid that I will have the saggy skin that many people who lose a lot of weight have. Don’t want to have surgery so I need to know the most effective possible way of avoiding skin sagging.

I am not a runner or an avid exerciser, and I have a desk job.
I never had a problem with my weight, but ever since I got into a relationship 1 year ago, I find myself about 20 pounds bigger than I used to be.
Easy workouts, little tips, simple things that will make it easier for me to lose the extra weight fast. I need to get this relationship weight off IMMEDIATELY! Please Help!