Metabolism and Aging
By Jean McLaurin
Obesity rates are climbing in the United States, and the numbers are staggering. More than 60 percent of Americans are overweight. It’s typical for people to gain about 15 pounds between age 20 and 65, as they become less active, and such weight gain is unlikely to put you at risk. But gaining more than that during adulthood can indeed be life threatening.
Your basal metabolic rate (BMR) is geared to the total calories you need each day to perform basic body functions. This doesn’t include calories burned during physical activity – just those required to maintain body temperature and facilitate digestion, breathing, pumping blood. Fueling these functions accounts for roughly 60 to 70 percent of the calories we expend in a typical day.
As we age, our BMR decreases, which means we need to intake fewer calories. At 70, one’s BMR is only approximately 85 percent of what it was at 30. At age 30, we also start to lose lean body mass at a rate of 2 to 3 percent per decade. The more muscle one has, the more calories the body burns. Ergo, fewer calories are burned as we lose muscle or lean body mass. Any unburned calories are stored as fat. Most of us continue to gain adipose (fat) tissue into our 60s, having it finally drop off approximately 10 percent between ages 70 and 80.
Many people gain weight as they age because they don’t cut back on calories even as they become more sedentary. This often leads to obesity, which can lead in turn to high blood pressure, high cholesterol levels, high triglycerides, and elevated blood glucose. A person who has several of these conditions is typically diagnosed with metabolic syndrome, or insulin-resistant syndrome at increased risk for heart disease, diabetes, and stroke.
In 2001 the National Cholesterol Education Program defined metabolic syndrome as follows:
• A waistline of 40 inches or more for men, 35 inches or more for women (measured across the belly);
• Blood pressure of 130/85 mm Hg, or higher;
• Triglyceride level above 150 mg/dl;
• Fasting blood-glucose (sugar) level greater than 100 mg/dl;
• A high-density lipoprotein level less than 40 mg/dl (men) or 50 mg/dl (women).
If a person has three or more of these conditions, he or she may be diagnosed with metabolic syndrome. A recent national survey showed that at least one in five Americans has metabolic syndrome, and more than 40 percent of people in their 60s and 70s are so affected.
The good news is there are non-invasive treatment options for metabolic-syndrome sufferers, and if followed, the development of heart disease, stroke, and Type 2 diabetes may be prevented. So becoming more active and losing weight can really help. Your doctor may in addition prescribe medications for conditions like high blood pressure and cholesterol.
Even a moderate weight loss, 5 to 10 percent of total body weight, can decrease insulin resistance. Exercise can also help reduce the risk of diabetes by increasing the ability of your cells to utilize insulin. An exercise program of 30 minutes of aerobic activity a day may lower blood pressure and cholesterol levels.
Consultation with a registered dietitian is important if you are diagnosed with metabolic syndrome. An overall dietary guide is 50 to 55 percent of calories from carbohydrates; 25 to 30 percent from fat (focusing mainly on monounsaturated fats, which help increase HDL levels or “good” cholesterol); 20 percent from protein. Following a diet that is low in simple carbohydrates (such as white rice and white bread) and includes more complex carbohydrates (such as brown rice and whole-grain breads) may also help control blood-sugar levels. Finally, increasing your consumption of fruits and vegetables to at least five servings a day, while cutting back on foods high in calories and saturated fat (such as red meat), may help lower cholesterol and triglyceride levels. Eating sensible portions and including a variety of healthy foods will help in every way.
Maintaining a healthy body weight is an essential part of staying fit throughout life. A varied diet of sensible portions coupled with regular exercise can greatly reduce risk of heart disease, stroke and diabetes. Setting the right goals is an important first step.
