"I am disgusted with the way you responded to my question...Not only did it not make any sense, but what you were saying was ridiculous, absurd, and physically impossible."

"...after giving birth to a baby eight months ago, and with having to let my body try and recover from gaining 87 lbs during the pregnancy...you would think that my body would have had some changes made to it. After a tiny 108 pound body stretches to almost double its size, you better bet that you're going to have some major stretched skin."

"The skin cannot go back in with just dieting alone because it doesn't have any more 'fat' underneath it to get rid of, and it doesn't have the extra layers of fat on the body to cover anymore, so it just hangs there, left as a reminder of how fat you once were, and how much your body was forced to stretch out to accommodate the large amount of weight that was gained. By exercising, the skin does pull in some-with the muscle, but there will still be excess skin left on the body that can't be 'starved off.'"

Many people would agree that this woman's argument appears to make sense. In such cases, plastic surgery is usually offered as the best solution to eliminate hanging remnants of excess, lax, or redundant skin, especially if the condition is associated with skin disorders. But, a closer look reveals this logic to be faulty. Is loose skin really unavoidable and inevitable after substantial weight loss? I believe the answer is no!

The human integumentary system (skin) is not a passive layer of tissue that remains stretched out like an empty plastic bag after losing large amounts of bodyweight. The argument of the woman above about the cause of loose skin is a myth. Rather, skin is a living organ, actively adapting to the body's internal and external environments. People on extended fasts consuming nothing more than water have demonstrated that the skin can lose 20% or more of its size.

The skin is usually thickest on the soles of the feet, and thinnest on the eyelids. As a typical example of your skin's thickness, pinch the skin on the back of your hand. If it were true, as this woman claims, that the folds of skin hanging off her body had absolutely no fat left underneath to diet away, every inch of this skin would hang in sheets as thin as fold of paper. 

However, common observation of the folds of skin in such examples reveals this is not usually the case. 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.

Age is claimed to be a factor that reduces skin elasticity and thus reduces the ability of the skin to readjust it's size after weight loss. However, many cases of loose skin are found in relatively young people who have lost weight, so the effect of age on skin elasticity is not really a factor in all cases, if at all. 

A change in a woman's body shape before and after normal pregnancy is another example of the skin's flexibility to snap back to normal size. By normal pregnancy, however, I mean without large accumulations of excess body fat, unlike the case of the woman above. 

The Cause of "Loose Skin"

Why does the skin sometimes take on this hanging appearance (e.g., abdominal pannus) during the course of losing large amounts of weight? Why is it that not everyone who loses weight has this problem? Why do we see flabby skin develop even in people who have lost much less weight? What is the difference between those people who suffer from flabby or loose skin, and those who achieve weight loss while completely or partially avoiding this problem?

In my opinion, the droopy appearance of folds of skin is most probably caused by crash diets that sacrifice large amounts of supporting muscle, or lean body mass. Even less severe diets and weight loss from bariatric surgery can result in a substantial amount of muscle loss over time. Perhaps future scientific research will show a correlation between loss of lean body mass on a diet with the development of redundant skin.

In the meanwhile, here's an example to illustrate how muscle loss on a diet can cause droopy folds of flabby, loose, skin. Let's say you start at a bodyweight of 115 pounds, in good toned shape with firm skin, but you gradually gain 100 pounds of body fat. You then go on some sort of crash weight-loss program or have bariatric surgery to quickly lose those 100 pounds. 

However, let's say not all of the weight you lose is body fat. Perhaps 20% of your lost weight is muscle. This is not unusual on a severe crash diet, and many people lose much more muscle than that on these diets. In fact, if you were to fast on just water, 60% of your weight loss would be muscle. 

And, because muscle can rapidly dehydrate and sacrifice protein to provide an additional supply of energy to your body, muscle loss increases the more active you are on a severe diet. But let's stick to a modest number of 20% muscle loss in this example.  

Now, after your severe diet, you have returned to your starting bodyweight of 115 pounds, but your internal body composition is altered. You have 20 fewer pounds of muscle on your body, and 20 more pounds of body fat, even though you weigh as much as you did before you put on the extra weight! The percentage of your bodyweight that is fat is now higher than before you gained weight.

Would you expect your body to look as shapely and firm under these circumstances, with a higher percentage of body fat? NO! At 115 pounds, body parts that used to be filled with toned muscle are now filled with a greater volume of flabby fat instead. Pound for pound, fat takes up more volume than muscle, pushing farther out until it begins to hang in folds of skin. Continuing on with your diet only exacerbates the problem as your muscle level drops even more. Even worse, if your bodyweight dips below your healthy starting point, you are now too thin, and covered with flabby skin!

Now, imagine the effect if you lose several hundred pounds of bodyweight, and your muscle loss is twice as much, 40-50% or more of lost bodyweight. Those voluminous folds of flab can become an enormous problem.

To eliminate and prevent the droopy appearance of the remnants of excess body fat during and following weight loss, without resorting to surgical procedures, you must change your body composition, not just lose bodyweight. That means paying particular attention to the ratio of your body fat to muscle, or lean body mass. Preventing loss of lean body mass while dieting to lose body fat will dramatically improve your appearance.

Almost every dieter has experienced rapid weight regain after dieting. Aside from regained body fat resulting from a return to overeating habits, many people don't realize that regained bodyweight can often include a significant amount of replenished lean body mass that was lost during dieting. They actually look and feel better—less haggard and with less droopy skin—after regaining this kind of lean weight. So, how is muscle lost on a diet, anyway? 

During a diet, a process called gluconeogenesis (which means a new source of glucose) allows your body to utilize both muscle and body fat to supply energy that is not provided by food. For each pound of body fat burned during gluconeogenesis, figure that about a pound and a half of muscle is also burned right along with it. Because a pound of muscle contains about 600 calories, that means for every pound of fat you lose on a diet, 3500 calories, you will have to eventually replenish about 900 calories from burned- off muscle to avoid a net loss of lean body mass. 

Periodically replenishing depleted lean body mass with controlled, small increases in your calorie intake is how you avoid an overall net loss of muscle during or after dieting. 

Because a muscle's volume consists of 70% fluid, muscle usually begins to replenish very rapidly as soon as you begin to increase your calorie intake back toward a normal maintenance intake amount. This replenishment helps provide the firmness and fullness to muscle that is lacking in flabby skin. However, you must take extreme care to avoid over-replenishment above maintenance calorie levels, which will start increasing your body fat level again! In effect, your dieting isn't really complete until you have fully replenished all your muscle losses. 

Lean body mass replenishment can occur in small daily amounts each dieting day, or in larger amounts over several days following a period of dieting or fasting. For example, on a moderate diet, only a portion of each dieting day is actually spent in a state of gluconeogenesis, when calorie intake dips below calorie expenditures. 

Muscle losses during the diet are replenished during other portions of the day when calorie intake rises above calorie expenditures. On the other hand, a person who fasts for several days is in a continuous state of gluconeogenesis, and often follows the fast with a controlled re-feeding period to restore healthy lean weight.

Monitoring body composition levels of lean body mass will guide you in determining the correct balance between your calorie intake and calorie expenditures, which will allow you to replenish and maintain levels of lean body mass that are burned while dieting. Experienced dieters often take a weekly "break day" from dieting, knowing that it recharges them. Regardless if replenishment occurs daily, every several days, or weekly or more, failure to restore burned lean body mass is the number one cause of "loose skin." 

It is possible to be at the ideal bodyweight according to Body Mass Index charts (BMI), but still have too much body fat and not enough lean body mass. For example, a young woman in her twenties with "loose skin" recently appeared on a popular radio talk show.  She had lost over two-hundred pounds in one year, and her bodyweight at 5' 8" was now in the 120's. Yet, her abdomen was covered with flabby skin that hung off of her. 

I would guess there is at least another 20 pounds of excess body fat stored in those folds of skin. However, if she lost another 20 pounds of bodyweight, she would obviously look like an emaciated stick! But, that's not because she is too low in body fat...it's because she lacks sufficient lean body mass! 

My suggestion to this young woman would be to replenish her lost lean body mass with a healthy balanced diet, and to tone her muscle with weight training (See Muscle Mass Myths). After increasing her bodyweight with 20 pounds of replenished lean body mass, she can then lose the rest of her excess body fat, without sacrificing any more lean body mass. Then she would have both a normal bodyweight AND a normal body composition.

What is required to avoid muscle loss during a diet, and gain back lost muscle, is an easy method to measure changes in one's body composition (muscle and body fat levels), and a method to monitor and modify one's energy balance, which is the balance between the calories one eats and burns each day. Such a method is available in The Body Fat Guide.