The innermost layer of your skin consists of proteins, including collagen and elastin. Collagen, which makes up 80% of your skin's structure, provides firmness and strength. According to research, Collagen and Elastin provide elasticity and helps your skin stay tight. Skin stretched during pregnancy often loses its ability to retract after weight loss due to damage to collagen, elastin and other components responsible for elasticity, so naturally improving Collagen intake helps to tighten loose skin.