Lost Weight = Loose Skin

If our jeans hang loose when we lose weight, it would make sense that our skin would as well. In cases of moderate weight loss, our skin shrinks back to fit the body's new size, thanks to its elasticity. A protein called collagen in the skin gives it this special property, which helps explain how we don't outgrow our skin as we get older. As we age, these collagen fibers in the skin weaken, leading to wrinkles.

Collagen does have its limits. Rapid growth or weight gain can outpace collagen production in the skin, causing areas to overstretch. This can lead to striations called stretch marks. These are particularly common with pregnancy and adolescents going through puberty. Although a number of lotions and creams on the market claim to get rid of stretch marks, most naturally go away on their own.
excess skin
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Massive weight loss can leave you with extra skin because it has lost elasticity.

Sometimes in cases of massive weight loss, people have folds of extra skin left over from their heavier days. Their skin had become so outstretched that it hangs limply from the thinner body, like worn out elastic.

As the number of obese people undergoing gastric bypass surgery increases, so do corrective surgeries for the unwanted and often uncomfortable loose skin. Although it may seem purely cosmetic, extra skin can actually cause infections, rashes and back problems. Since it's a highly invasive procedure, plastic surgeons may space out skin tucks and removals over months or a year, costing up to $100,000.

Even after the work is done, patients wear lifelong scars from the surgeries. Also, this type of body recontouring comes with risks. Since it's a relatively new procedure, doctors only know anecdotal evidence of complications, including dead skin, infection and open wounds [source: Singer]. But as beltlines continue to bulge, the numbers of patients will likely increase as it has the past decade.

Surgery Stats
In 2007, at least 62,964 men and women in the U.S. received tummy tucks to the tune of more than $781 million. Liposuction was the second most common type of plastic surgery performed, with 302,000 people getting fat sucked out of their bodies for more than $900 million combined. [source: American Society of Plastic Surgery].