Aging's Effects on the Body
There are essentially two ways that we age. The first is called primary aging. "That happens at the cellular level and includes attacks on our cells by free radicals, DNA damage and the wear and tear on cells, tissues and organs from constant ongoing chemical and other reactions that constitute metabolism," explains Donald Williamson, PhD, an anti-aging researcher and the John Stauffer McIlhenny Professor in Nutrition at Pennington Biomedical Research Center in Louisiana. "Secondary aging is developing a disease such as cancer, atherosclerosis or diabetes, which can shorten the life span."
Some aspects of aging are obvious. It's apparent, for instance, that the skin changes. Layers within and beneath the skin become thinner, helping to cause sagging and wrinkles—the skin, in a sense, folds in on itself. The skin also becomes less elastic and drier. It grows to be less sensitive to touch, too, and becomes less adept at regulating the body's temperature. Hair loses pigment (the reason we become gray) and hair volume is lost in both men and women.
Body shape can change too. Most people gain fat, and in many women, fat storage shifts from the hips and thighs to the abdomen. This deep intra-abdominal fat is one of the reasons that the risk of heart disease and diabetes in women dramatically increases after menopause. 

One of the more noticeable signs that someone is growing older is the sudden appearance of reading glasses on his or her face. As the lens of the eye becomes less flexible, it makes it harder to focus on objects in the near distance. Vision in dim light also diminishes, and cataracts—clouded lenses—can start forming as early as age 40.
There are also many changes that you can't see, and these changes have an impact on secondary aging. For instance, the thymus, a gland central to the immune system, shrinks, and many of the immune cells decrease in their ability to battle bacteria, viruses and even cancer cells. The heart muscle degenerates slightly, and the valves inside the heart become thicker and stiffer. Arteries are more likely to get clogged with plaque, and blood pressure may increase. The function of most organs declines as well, and cells become less able to divide and reproduce. Some hormone levels rise while others drop, changing the characteristics of many physiological processes such as metabolism and insulin sensitivity. Our sleep architecture—the different stages of sleep—shifts so that we spend less time in deep, refreshing sleep and more time in the lighter phases from which we're more easily awakened.
Significant changes in the muscles, bones and joints start to occur as well. Muscle fibers shrink and the repair of muscle tissue slows, lowering strength, decreasing the rate at which calories are burned and making the body more susceptible to obesity. The joints become stiffer and bone mass is lost, increasing the risk of osteoporosis. The vertebrae can also become more compressed, the reason why many people lose height as they grow older.

The Light at the End of the Tunnel
Just reading all of the above, I know, can cause you some despair. No one likes to think of their body (and especially their mind) deteriorating. But there's room for optimism, because you can really make a difference in the rate at which you age and how susceptible you become to age-related diseases. Everything I describe above can happen, but it doesn't have to: How you live can have a significant impact on how your body ages. In the following chapters, you'll learn about how exercise, good nutrition, skincare and healthy sleep habits actually change your physiology. Your body will grow chronologically older; there is nothing you can do about that. But you can get physiologically younger. Successful aging isn't an oxymoron. By adhering to the advice in this book, you can substantially lower your likelihood of disease, look and feel younger, and stay strong, vital, sharp, active and happy. Work at it and you can even turn back the clock 20 years or more—no exaggeration.
Reprinted from the book 20 YEARS YOUNGER by Bob Greene. Copyright ©2011 by Bob Greene. Reprinted with permission of Little, Brown and Company. All rights reserved.


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