Chapter
4
Physical Activity
from Dietary Guidelines for Americans
Contents
Americans tend to be relatively inactive. In 2002, 25 percent of adult
Americans did not participate in any leisure time physical activities in the
past month, and in 2003, 38 percent of students
in grades 9 to 12 viewed television 3 or more hours per day. Regular physical
activity and physical fitness make important contributions to one's health,
sense of well-being, and maintenance of a healthy body weight. Physical activity
is defined as any bodily movement produced by skeletal muscles resulting in
energy expenditure.
In contrast, physical fitness is a
multi-component trait related to the ability to perform physical activity.
Maintenance of good physical fitness enables one to meet the physical demands of
work and leisure comfortably. People with higher levels of physical fitness are
also at lower risk of developing chronic disease. Conversely, a sedentary
lifestyle increases risk for overweight and obesity and many chronic diseases,
including coronary artery disease, hypertension, type 2 diabetes, osteoporosis,
and certain types of cancer. Overall, mortality rates from all causes of death
are lower in physically active people than in sedentary people. Also, physical
activity can aid in managing mild to moderate depression and anxiety.
- Engage in regular physical activity and reduce sedentary activities to
promote health, psychological well-being, and a healthy body weight.
- To reduce the risk of chronic disease in adulthood: Engage in at
least 30 minutes of moderate-intensity physical activity, above usual
activity, at work or home on most days of the week.
- For most people, greater health benefits can be obtained by engaging
in physical activity of more vigorous intensity or longer duration.
- To help manage body weight and prevent gradual, unhealthy body
weight gain in adulthood: Engage in approximately 60 minutes of
moderate- to vigorous-intensity activity on most days of the week while
not exceeding caloric intake requirements.
- To sustain weight loss in adulthood: Participate in at least 60 to
90 minutes of daily moderate-intensity physical activity while not
exceeding caloric intake requirements. Some people may need to consult
with a healthcare provider before participating in this level of
activity.
- Achieve physical fitness by including cardiovascular conditioning,
stretching exercises for flexibility, and resistance exercises or
calisthenics for muscle strength and endurance.
- Children and adolescents. Engage in at least 60 minutes of physical
activity on most, preferably all, days of the week.
- Pregnant women. In the absence of medical or obstetric complications,
incorporate 30 minutes or more of moderate-intensity physical activity on
most, if not all, days of the week. Avoid activities with a high risk of
falling or abdominal trauma.
- Breastfeeding women. Be aware that neither acute nor regular exercise
adversely affects the mother's ability to successfully breastfeed.
- Older adults. Participate in regular physical activity to reduce
functional declines associated with aging and to achieve the other
benefits of physical activity identified for all adults.
Reduction of Health Risks
Regular physical activity has been shown to reduce the risk of certain
chronic diseases, including high blood pressure, stroke, coronary artery
disease, type 2 diabetes, colon cancer and osteoporosis. Therefore, to reduce
the risk of chronic disease, it is recommended that adults engage in at least 30
minutes of moderate-intensity physical activity on most, preferably all, days of
the week. For most people, greater health benefits can be obtained by engaging
in physical activity of more vigorous intensity or of longer duration. In
addition, physical activity appears to promote psychological well-being and
reduce feelings of mild to moderate depression and anxiety.
Achieving and
Maintaining Healthy Body Weight
Regular physical activity is also a key factor
in achieving and maintaining a healthy body weight for adults and children. To
prevent the gradual accumulation of excess weight in adulthood, up to 30
additional minutes per day may be required over the 30 minutes for reduction of
chronic disease risk and other health benefits. That is, approximately 60
minutes of moderate- to vigorous-intensity physical activity on most days of the
week may be needed to prevent unhealthy weight gain. While moderate-intensity physical
activity can achieve the desired goal, vigorous-intensity physical activity
generally provides more benefits than moderate-intensity physical activity.
Control of caloric intake is also advisable. However, to sustain weight loss for
previously overweight/obese people, about 60 to 90 minutes of moderate-intensity
physical activity per day is recommended.
Most adults do not need to see their healthcare provider before starting a
moderate-intensity physical activity program. However, men older than 40 years
and women older than 50 years who plan a vigorous program or who have either
chronic disease or risk factors for chronic disease should consult their
physician to design a safe, effective program. It is also important during
leisure time to limit sedentary behaviors, such as television watching and video
viewing, and replace them with activities requiring more movement. Reducing
these sedentary activities appears to be helpful in treating and preventing
overweight among children and adolescents.
Different intensities and types of exercise confer different benefits.
Vigorous physical activity (e.g., jogging or other aerobic exercise) provides
greater benefits for physical fitness than does moderate physical activity and
burns more calories per unit of time. Resistance exercise (such as weight
training, using weight machines, and resistance band workouts) increases
muscular strength and endurance and maintains or increases muscle mass. These
benefits are seen in adolescents, adults, and older adults who perform
resistance exercises on 2 or more days per week. Also, weight-bearing exercise
has the potential to reduce the risk of osteoporosis by increasing peak bone
mass during growth, maintaining peak bone mass during adulthood, and reducing
the rate of bone loss during aging. In addition, regular exercise can help
prevent falls, which is of particular importance for older adults.
Make Time to
Exercise
The barrier often given for a failure to be physically active is lack of
time. Setting aside 30 to 60 consecutive minutes each day for planned exercise
is one way to obtain physical activity, but it is not the only way. Physical
activity may include short bouts (e.g., 10-minute bouts) of moderate-intensity
activity. The accumulated total is what is important—both for health and for
burning calories. Physical activity can be accumulated through three to six
10-minute bouts over the course of a day.
Elevating the level of daily physical activity may also provide indirect
nutritional benefits. A sedentary lifestyle limits the number of calories that
can be consumed without gaining weight. The higher a person's physical activity
level, the higher his or her energy requirement and the easier it is to plan a
daily food intake pattern that meets recommended nutrient requirements.
Proper Hydration
Proper hydration is important when
participating in physical activity. Two steps that help avoid dehydration during
prolonged physical activity or when it is hot include: (1) consuming fluid
regularly during the activity and (2) drinking several glasses of water or other
fluid after the physical activity is completed.
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