There's nothing worse than working your way through a diet only to end up with skin that hangs like a curtain from a window. Unfortunately, it's a common byproduct of weight loss. Here's what you can to minimise the amount of loose skin during weight loss or even improve the issue after you've lost weight.
Why Loose Skin Happens
First, let's take a look at the anatomy of your skin and the surrounding area. Two layers of tissue reside underneath your skin: adipose (or fat) followed by muscle tissue directly beneath. Both fat and muscle push up against the adjacent layer of skin, keeping it relatively taught before you lose weight.
The issue of loose skin begins long before any weight loss occurs. Instead, it starts when a large amount of weight is gained. When you gain weight, your skin's surface area increases to accommodate the new fat tissue (which is why "stretch marks" sometimes occur).
While your fat cells shrink when that weight is lost, you still retain the same surface area. The new void under the larger surface area creates a layer of skin that may "hang", because there is less tissue underneath taking up space. This is what's known as loose or "sagging" skin.
The amount of loose skin that remains varies by individual. In fact, not everyone's skin sags afterwards, and it depends on several factors: total weight gained and lost, age, total muscle mass and genetics among them.
Some people have a massive amount of loose skin that only surgery can fix. Others have none at all, despite significant weight loss. You can see an example of the latter case in this person's before and after.
Then there are those in the middle, where there's room to prevent loose skin during weight loss as well as improve it afterwards. I have personal experience with this. After going from 230 to 150 pounds, my skin was loose and even (apologies in advance for the visual) "pullable" away from my body. I looked like the ugly bastard child created by a Shar-Pei and a jar of silly putty. My skin is no longer loose -- suggesting that in non-extreme cases, it can be improved to a degree -- but it could have been prevented using the methods below.
Muscle Tissue: The Key To Minimising Loose Skin
Maintaining or increasing muscle tissue is the key to minimising loose skin. Remember, the phenomenon occurs when the underlying layers of tissue shrink under a much large surface area. If muscle mass is lost in addition to fat, it creates an even larger void under your skin's surface. On the other hand, increasing lean tissue fills the area underneath the skin, keeping it taught.
There are a few ways that you can go about retaining or even increasing your muscle tissue during a diet.
Lose Weight At A Reasonable Pace
There's a correlation between how quickly one loses weight and the amount of loose skin they end up with.
In order to lose weight, you must create a calorie deficit. When the deficit is reasonable and you're losing up to a kilo per week, a majority of the weight lost is fat. While a more aggressive deficit will result in faster weight loss, there's a higher risk that this weight loss will come from muscle tissue, especially when done over a prolonged period of time.
Keep a slow and steady pace and a caloric deficit of around 15% below your maintenance calories. You'll retain much more muscle tissue, thus keeping your skin "tight".
Incorporate Strength Training Into Your Regimen
For the reasons discussed above, incorporating strength training will allow you to maintain more muscle mass, or even build muscle if you're relatively new to this type of regimen. In your first year of resistance training, you may actually be able to build up to 10 kilos of muscle. (This will likely be less if you're dieting, given that a caloric deficit is not the optimum conditions for building muscle.)
A hypertrophy (muscle building) regimen may yield better results over one that optimises strength or endurance. Hypertrophy training specialises in increasing the overall size and volume of your muscles, allowing your skin to cling tighter to the underlying tissue.
Lastly, make sure to keep protein intake high. During caloric deficit this will not only prevent the loss of lean mass (or "muscle catabolization"), but also ensure that you have the optimum amount for building muscle. You can use the "Alan Aragon" rule to find your minimum daily protein target.
Get Even Leaner
I've observed that loose skin is less of an issue for those who get down to lower levels of bodyfat -- around 10% bodyfat for men and 20% for women. Of course, this could simply be due to survival bias. For example, perhaps folks without loose skin issues in the first place are more motivated to keep continuing their progress. But Dr Ron Brown, author of "The Body Fat Guide" doesn't think so, and has a compelling explanation: what many perceive as "loose skin" is actually excess fat.
Measuring the thickness of these hanging folds of skin provides evidence that there is still a substantial amount of body fat underneath the skin. The skin is not so much "loose" as it is flabby due to excess body fat. Even if some areas have completely thinned out, excess body fat is likely to be stored in adjacent areas that contribute to the overall flabby condition.
Still, there are certainly cases where nothing short of surgery will help. But there is evidence to suggest that loose skin issues can be improved by losing more fat.
"Just get even leaner" is easier said than done, obviously. Getting to the required level of bodyfat may take years, even decades, but fitness is a never ending journey anyway. Still, there's comfort in knowing that if you have loose skin, some level of improvement is still under your control without the need for surgery.
Lifehacker's Vitals column offers health and fitness advice based on solid research and real-world experience.