The Aging Process

Metabolic Effects of Aging

As you get older, it's normal to gain weight, right? It may be normal -- if you define "normal" as "common" -- but it's not desirable, and it's not inevitable either. Chances are, you weigh more now than you did ten years ago. Or maybe your waistline has expanded, but the scale's remained steady.

Understanding what happens with weight as your body ages will help you to control it. Beginning around age 25, total body fat starts to increase, while muscle mass and body water decrease. As a result, you may weigh more as you age or lose some of your youthful muscle tone.

Why has your shape gone south? A lower basal metabolic rate (BMR) is to blame. BMR is the number of calories you burn daily to fuel involuntary body functions, such as your heartbeat, brain function, and digestion. BMR is dependent upon body composition. The more muscle you have, the more calories you burn, 24 hours a day. That's because muscle is a high-maintenance tissue and requires more calories than fat to sustain itself.

The decline in muscle mass that begins in your twenties, coupled with a decrease in activity level, means that you need fewer calories in your sixties than you did in your teens. For example, a 180-pound male's BMR accounts for about 1,930 calories a day between the ages of 18 and 30.

After age 60, his body needs about 350 fewer calories to maintain his weight and good health. If you're still eating like a teenager by the time you're 60, and you haven't increased your physical activity, you'll definitely be putting on pounds.

For women, menopause often means weight gain. When the ovaries stop producing the hormone estrogen, muscle mass may diminish to the point of lowering BMR. When that happens, women gain a significant amount of fat, usually in the abdomen, even without consuming more calories.

Speaking of the abdomen, where you store extra fat also affects your health.

If you're shaped like an apple -- packing fat in your mid-section -- you're at greater risk for heart disease than if you're shaped like a pear -- gaining weight around your hips and buttocks. Excess weight in any location also boosts your chances for developing certain cancers and diabetes, and it also aggravates arthritis in your hips and knees.

Respiratory Changes

As you age, your lungs become less elastic, and your chest wall stiffens. In addition, the expansion of your trachea contributes to a decreased surface area in your lungs. You can't cough as forcefully, which also diminishes your ability to clear germs from your lungs. That's why older people are more prone to upper respiratory infections, such as colds.

If you ever smoked, your respiratory potential is reduced in your later years. Older adults also experience some difficulties with swallowing, which increases the chances of aspirating particles of food or other substances into the lungs. Aspiration is a common cause of pneumonia in older adults.

Lung capacity and function drop off with time, which means you may be more winded after climbing a flight of stairs or taking a walk than you were 20 years ago, but exercise heads off some of the changes to the lungs and entire respiratory system. Physically active older people who regularly participate in aerobic exercises, including walking and cycling, are way ahead of the curve.

Their aerobic capacity is far greater than their peers who don't exercise, and better than younger, sedentary people. In fact, well-conditioned older people may reach levels of lung function that exceed those of much younger people. A generous intake of vitamin C also helps maintain pulmonary function as you age. Loss of pulmonary function is a major predictor of disease and death in older adults.

Exercise Your Acumen

If new situations make you squirm, maybe you should exercise more often. What's the connection? As you age, it takes more time for your brain to process new information, so you may avoid unfamiliar surroundings for the sake of comfort. But that limits your world.

Regular exercise can help you expand your horizons. Studies show that the most physically fit older people best tolerate unfamiliar surroundings. Physical fitness helps you react more quickly to new situations, new faces, or a new social setting, perhaps adapting as quickly as someone much younger.

Continue to the next and final page of this article to learn about the sensory effects of aging and find out if you're at risk.

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