Sustainability is defined as the endurance of systems and processes. Meaning making changes that will last and endure time.
What does that mean in terms of getting fit and fitness goals? You need to find what works for you and what you enjoy because that’s what will last. Taking pills and get fit quick diets do not work because they are not sustainable.
If you use a diet and lose 40 pounds a month but then you have too take time off of said diet, pills, or whatever you are using. You will gain all of that weight back faster than you lost it in the first place.
Thats really why sustainability is key in reality fitness has little to do with how you look and how healthy your body is. Although there are tons of different fitness levels and types of fitness the under lying key is find exercise that you enjoy to do, so you are more willing to do it. Then eat an all around healthy diet that fit your goals, it’s that simple. Just stick with that and you will make progress in no time and sustain that progress for the rest of your life.