Treat the surface without understanding what loosened it and the result rarely holds. That is why the first job at your consultation is to work out what is driving your skin laxity. As such, a handful of factors account for almost all of it.
Ageing sits at the top. Then, from the mid-twenties onward the skin makes a little less collagen each year, and elastin frays with it. So, firmness fades slowly and steadily whatever else you do. Sun exposure speeds the whole process up. This is because ultraviolet light breaks down collagen and elastin far faster than time alone. As a result, sun-exposed skin on the face, neck and hands tends to slacken first.
Weight change is the next big driver. Skin that was stretched over a larger frame does not always shrink back once the volume behind it goes. In turn, this can follow weight gain, weight loss or pregnancy. As a result, it can be left loose across the tummy, arms and knees. Smoking starves the skin of oxygen and strips collagen. Genetics, meanwhile, set the baseline. That is why firmness runs in some families and slackness in others. Because ultraviolet accelerates nearly every one of these, a daily broad-spectrum SPF is not an optional extra. It is the one habit that protects both your skin and your results.