According to the Mayo Clinic, your metabolism is nothing more and nothing less than "the process by which your body converts what you eat and drink into energy." This isn't just the energy for movement. In fact, your basal metabolic rate burns as much as 70 percent of all the calories you burn each day because the simple maintenance of the body's functions (i.e. breathing, circulation, digestion, cell repair and replacement) requires so much energy.

The rest of the calories your body burns is based on how active you are each day. This is why people with sedentary lifestyles have lower calorie requirements than professional athletes or those whose work requires heavy lifting or frequent movement. You gain weight when you consume more calories than you burn.

Age and muscle mass negatively affect metabolism

Your metabolic rate peaks in your early 20s, according to Women's Health Magazine. At this age, you tend to have a higher muscle mass and have a fair amount of physical activity built into your day. As early as age 30, however, men and women begin noticing a dip in their ability to lose weight. This could coincide with the age when they start buckling into careers that keep them stationary for most of the day.

Around age 40, your body will naturally begin to lose muscle mass in a process known as sarcopenia. "Physically inactive people can lose as much as 3 percent to 5 percent of their muscle mass each decade after age 30. Even if you are active, you’ll still have some muscle loss," WebMD explains.

As fat replaces muscle, you'll burn calories more slowly, which leads to a sluggish metabolism and possible weight gain. Hormones and genetic factors are also thought to have an impact on how a person's metabolism changes as he or she ages.

A sluggish metabolism may lead to obesity

Obesity, which often results from the slowed metabolism seen in older adults, is known to have a host of negative side effects on the body. A study published in the Online Journal of Issues in Nursing lists a few of these possible corollaries, including hypertension, respiratory issues, arthritis, heart disease, high cholesterol, diabetes, impaired cognitive function and lower quality of life. Though these effects are detrimental at any stage of life, they can be especially damaging to aging adults who might be experiencing other diseases or pain incident to age.

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For those who aren't in the habit of frequent exercise, the key is just to start moving. "Chair-living has proven so enticing that we have forsaken our legs. It is now time to find ways to get us back onto our legs," said James A. Levine, M.D., Ph.D., of the Division of Endocrinology, Diabetes, Metabolism, and Nutrition at Mayo Clinic Rochester. His research on nonexercise activity thermogenesis has found that those who make an effort to move more frequently throughout the day maintain muscle mass and burn more calories than those who are mainly sedentary with sporadic attempts to visit the gym.

Dr. Walter Medlin, a weight-loss surgeon at Salt Lake Regional Medical Center, also proposed a few tips for how adults can maintain a healthy weight even as they age. "It's important just to stay healthy in general," Medlin said. "A high BMI puts you at risk for metabolic diseases like premature cardiac death and diabetes. Mechanically, more weight puts more stress on joints as we age."

To prevent this weight gain, Medlin suggested that people should "track their weight and maintain muscle mass. Properly treating medical issues" is another important part of sustaining a healthy lifestyle. "People don't realize how quickly muscle mass diminishes," he went on. "Physical therapy just gets people started. It can take up to a year to regain muscle mass lost by just a few weeks of bed rest. It's important they keep exercising consistently." Before starting any new exercise program, make sure you check with your doctor to find out what kinds of fitness activities could be right for you.

Salt Lake Regional Medical Center cares about your health. For more information on how to get started on your weight-loss journey, visit saltlakeregional.com.

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