Stimulate Metabolism with Exercise
Stimulate Metabolism with Exercise
Approximately 60 percent to 75 percent of the energy liberated from food is expended to maintain the essential functions of the body. The energy to accomplish these functions is the basal metabolic rate (BMR) – the minimum amount of energy that the body expends to sustain life while at complete rest. The BMR is measured at least 12 hours since the last meal, after 8 hours of sleep, and in a thermally neutral environment (at a comfortable room temperature). Because these conditions are difficult to satisfy, they often are approximated, so that the BMR is estimated by the resting metabolic rate (RMR) The RMR requires that measurements be taken 3 to 4 hours after the last meal, following a 30-minute rest period, in a thermally comfortable environment, on a day in which the person has not participated in vigorous physical activity.
Because of less muscle and more fat, the RMR of females is 5 percent to 10 percent lower than males and 15 percent lower than that of very muscular males. Males who are overweight primarily because of heavy musculature have higher RMRs and respond more readily to exercise/diet approaches to weight loss than overweight men whose excess weight is primarily fat. The energy needed to sustain the RMR constitutes a significant amount of the total number of daily calories expended by the average adult. Then, from a weight-management perspective, it is advantageous to preserve or enhance the RMR and to do nothing to reduce it. Exercise fits the bill nicely, particularly resistive exercises that build muscle.
A persistent misconception regarding exercise is that it does not burn enough calories to make the effort worthwhile. Actually, consistent participation in aerobic exercise (such as walking, jogging, cycling, rowing, and aerobic dance) will burn substantial kcals. Anaerobic activities such as weight training do not burn many kcals during the workout, but they build the muscle tissue that will require more kcals later.
Muscle-building activities are an investment in future weight control. In the long run, the increase in muscle mass increases metabolism so the body’s kcal requirements increase even at rest. This is why activities for both cardiorespiratory development and muscular development are suggested for weight loss or weight maintenance or, for that matter, any well-rounded physical fitness program.
In the past, the decline in RMR was presumed to be a natural part of aging. But age per se is responsible for only half of the decline while the reduction in physical activity that all too often accompanies aging is responsible for the remainder. Disuse atrophy, the loss of muscle tissue from lack of effective stimulation, has a significant negative impact on the RMR because muscle is more metabolically active than fat – it uses more calories than fat under any of life’s conditions.
Authorities estimate that we lose 3 percent to 5 percent of our active protoplasm (mostly muscle tissue) each decade after 25 years of age. This loss is attributed directly to physical inactivity as we age and results in the all too common negative changes in body composition (an increase in fat and a decrease in lean body mass).
Physical activity is one of the keys to weight management because it uses calories and accelerates metabolism. It also prevents or attenuates the weight-loss plateau that the majority of dieters experience. This plateau represents a period of time when weight loss decelerates substantially or stops temporarily.
For example, young and middle-aged individuals who were within plus or minus 5 percent of their ideal weight, as determined by height, weight, and frame size charts, illustrated the body composition changes that occur with age and physical inactivity. Although both groups were within the ideal range for weight, the middle-aged subjects had twice as much body fat as the young subjects. These data show quite well that lost muscle weight that is replaced by a gain in fat weight produces negative changes in body composition even in the absence of weight gain. Fat is less dense than muscle, so it occupies more room in the body; hence, the change in the configuration of the body.