As we age, our bodies naturally make less collagen. And the collagen in the deep skin layers deteriorates, changing from a structured network of fibers to a disorganized jumble.
But lifestyle and dietary factors can cause collagen production to drop more quickly as well. Too much sun exposure, smoking, excess alcohol, and lack of sleep and exercise can all damage collagen fibers reducing their thickness and strength, leading to sagging skin and wrinkles.
Collagen is also broken down by eating a high sugar diet, so you need to keep an eye on that too.