Muscle growth cannot tighten skin after weight loss.
After extreme weight loss, you may find that you have excess skin in areas where there were fat tissue deposits. Your skin's natural elastic properties may tighten these areas automatically; however, the extent to which your skin could naturally tighten depends upon the amount of excess weight and length of time you carried the weight. Muscle growth, as aided by exercise with a focus on weight training, won't tighten loose skin but it can fill in loose skin to make it appear tighter.
Although building muscle can improve your appearance after extreme weight loss, you will likely have a significant amount of loose skin.
Understand Why Sagging Happens
It's a well known fact that skin is actually an organ, your body's largest. To better protect your internal organs and tissues, your skin is composed of multiple layers of cells that contain collagen and elastin, two substances that give skin its flexible, elastic qualities. Underneath your skin are layers of fat deposits, which vary in size for each individual based on total body-fat percentage. The elastic properties in your skin will stretch out to accommodate large fat deposits. Thus, after dramatic weight loss, your skin may still be stretched out and appear wrinkled and saggy from large fat deposits.
Add Bulk with Muscle
Exercise cannot cause muscles to pull skin tighter or shrink it back to size. However, as your muscles grow and develop, they can fill the excess skin left from weight loss, stretching and smoothing the outermost layers of skin for a more even, youthful and healthy look. Think of blowing up a balloon. As it fills with air, its surface becomes more stretched and shiny. So too does your skin as you tone and develop your muscles to replace the empty, sagging skin.
Do Exercises to Improve Muscle Growth
Toning exercises are effective for muscle growth. These include high-repetition weight training, plyometric exercises and resistance exercises, such as leg lifts with resistance bands. Cardiovascular exercise can help as well. While it will not cause large muscle growth that can fill areas of sagging skin, it does promote fresh oxygen flow to every organ, including the skin, which can cause skin regeneration that provides a smoother, less saggy look.
Manage Your Expectations
According to the Cleveland Clinic, it can take up to two years to see results from exercise, and success rates vary. Your results can depend on various factors, including age and amount of weight lost. You can do other things besides exercise to tighten your skin, including drinking plenty of water and eating a healthy, well-rounded diet. Focus on eating plenty of heart-healthy fats, as they contribute to skin elasticity and rejuvenation.