The Nutrition Source The Benefits of Physical Activity

Staying Active: Introduction

Although there are no sure-fire recipes for good health, the mixture of healthy eating and regular exercise comes awfully close. Most of The Nutrition Source is dedicated to singing the praises of a good diet. This is where physical activity gets its due.

• Exercise and Weight Control: How much exercise do you need to lose weight or keep it off?
• 20 Exercise Tips: Twenty ways to help you fit exercise into your life
• Exercise Guidelines for Children, Adults, and Older Adults: The latest U.S. government recommendations on physical activity
• Strength and Flexibility Training: Learn about exercise's benefits beyond the heart
• Exercise Safety: Tips for lowering your risk of exercise-related injuries
• How Hard are You Exercising? Learn how to use the Borg Scale to see if you're exercising hard enough 
• Active Communities: How our surroundings influence our level of activity, and what you can do about it

Regular exercise or physical activity helps many of the body's systems function better, keeps heart disease, diabetes, and a host of other diseases at bay, and is a key ingredient for losing weight. According to the 2008 Physical Activity Guidelines for Americans, (1) being physically active on a regular basis

• Improves your chances of living longer and living healthier
• Helps protect you from developing heart disease and stroke or its precursors, high blood pressure and undesirable blood lipid patterns
• Helps protect you from developing certain cancers, including colon and breast cancer, and possibly lung and endometrial (uterine lining) cancer
• Helps prevent type 2 diabetes (what was once called adult-onset diabetes) and metabolic syndrome (a constellation of risk factors that increases the chances of developing heart disease and diabetes; read more about simple steps to prevent diabetes)
• Helps prevent the insidious loss of bone known as osteoporosis
• Reduces the risk of falling and improves cognitive function among older adults
• Relieves symptoms of depression and anxiety and improves mood
• Prevents weight gain, promotes weight loss (when combined with a lower-calorie diet), and helps keep weight off after weight loss
• Improves heart-lung and muscle fitness
• Improves sleep

The Cost of Inactivity

If exercise and regular physical activity benefit the body, a sedentary lifestyle does the opposite, increasing the chances of becoming overweight and developing a number of chronic diseases. According to analyses by a team from the Centers for Disease Control (CDC) and Prevention, inactivity was associated with more than 9 million cases of cardiovascular disease in 2001, at an estimated direct medical cost of nearly $24 billion. (2) Another CDC analysis suggests that because individuals who are physically active have significantly lower annual direct medical costs than those who are inactive, getting people to become more active could cut yearly medical costs in the U.S. by more than $70 billion. (3)

Despite all the good things going for it, only about 30 percent of adult Americans report they get regular physical activity during their leisure time—and about 40 percent of Americans say they get no leisure-time physical activity at all. (25) Studies  that measure people’s physical activity using special motion sensors (called accelerometers) suggest that self-reports of physical activity probably are over-estimated. (26).

Being a “couch potato” may be harmful even for people who get regular exercise. (4) The Nurses’ Health Study, for example, is one of many, many studies to find a strong link between television watching and obesity. (5) Researchers followed more than 50,000 middle-aged women for six years, surveying their diet and activity habits. They found that for every two hours the women spent watching television each day, they had a 23 percent higher risk of becoming obese and 14 percent higher risk of developing diabetes. Interestingly, it didn’t matter if the women were avid exercisers: The more television they watched, the more likely they were to gain weight or develop diabetes
regardless of how much leisure-time activity and walking they did. Long hours of sitting at work also increased the risk of obesity and diabetes. More recently, studies have found that people who spend more time each day watching television, sitting, or riding in cars  have a greater chance of dying early than people who spend less time on their duffs. (6-8) Researchers speculate that sitting for hours on end may change peoples’ metabolism in ways that promote obesity, heart disease, diabetes, and other chronic conditions. (4, 7) It is also possible that sitting is a marker for a broader sedentary lifestyle.
In sum, a morning jog or brisk lunchtime walk brings many health benefits—but these may not entirely make up for a day spent in front of the computer or an evening in front of the television set. So as you plan your daily activity routine, remember that cutting down on “sit time” may be just as important as increasing “fit time.”

Physical Activity Guidelines: How Much Exercise Do You Need?

If you don't currently exercise and aren't very active during the day, any increase in exercise or physical activity is good for you. Aerobic physical activity—any activity that causes a noticeable increase in your heart rate—is especially beneficial for disease prevention. Some studies show that walking briskly for even one to two hours a week (15 to 20 minutes a day) starts to decrease the chances of having a heart attack or stroke, developing diabetes, or dying prematurely. (Brisk is a relative term; read more about exercise intensity.)
The 2008 Physical Activity Guidelines for Americans recommends that healthy adults get a minimum of 2-1/2 hours per week of moderate-intensity aerobic activity, or get a minimum of 1-1/4 hours per week of vigorous-intensity aerobic activity, or a combination of the two. (1) To lower your risk of injury, it’s best to spread out your activity over a few days in of the week. (Read more about how to exercise safely.)
You can combine moderate and vigorous exercise over the course of the week—say, by doing 20 to 25 minutes of more vigorous intensity activity on two days, and then doing 30 minutes of moderate intensity activity on two days. It’s fine to break up your activity into smaller bursts, as long as you sustain the activity for at least 10 minutes. Adults should also do muscle-strengthening activities on at least two days for the week. Children should get at least 1 hour or more a day of physical activity in age-appropriate activities. Healthy older adults should follow the guidelines for adults.   

Exercise Intensity: What’s Moderate, What’s Vigorous?

Moderate-intensity aerobic activity is any activity that causes a slight but noticeable increase in breathing and heart rate. One way to gauge moderate activity is with the "talk test"—exercising hard enough to break a sweat but not so hard you can't comfortably carry on a conversation. Vigorous-intensity aerobic activity causes more rapid breathing and a greater increase in heart rate, but you should still be able to carry on a conversation—with shorter sentences. 
Keep in mind that what feels like moderate activity for one person may actually be very vigorous activity for another: A typical young marathon runner, for example, could walk at a 4-mile-per-hour pace without breaking a sweat. But this same pace would likely feel very vigorous for the typical 90-year-old person.
One way to gauge how hard you are exercising is to use the Borg Scale of Perceived Exertion. It's a relative scale that matches how hard you feel you are working with numbers from 6 to 20. Exercise experts measure activity in a different way, using metabolic equivalents, or METs.

Walking—and Bicycling—Your Way to Health

Walking is an ideal exercise for many people—it doesn't require any special equipment, can be done any time, any place, and is generally very safe. What's more, studies such as the Nurses' Health Study, (9, 10) Health Professionals Follow-up Study, (11) Women's Health Study, (12)  Harvard Alumni Health Study, (13) National Health Interview Survey, (14) Women's Health Initiative, (15) Honolulu Heart Program, (16) Black Women’s Health Study, (17) and others (18, 19) have demonstrated that this simple form of exercise substantially reduces the chances of developing heart disease, stroke, and diabetes in different populations.
Though walking has health benefits at any pace, brisk walking (at least 3 miles per hour) is more beneficial than slow walking for weight control (20-22). And a recent report from the Nurses’ Health Study II suggests that bicycling offers similar benefits to brisk walking: (22) Researchers followed more than 18,000 women for 16 years to study the relationship between changes in physical activity and weight. On average, women gained about 20 pounds over the course of the study. Women who increased their physical activity by 30 minutes per day gained less weight than women whose activity levels stayed steady. But the type of activity made a difference: Women who added bicycling or brisk walking to their activity regimens were able to curb their weight gain, but women who added slow walking were not.
Brisk walking may be challenging for some people, and bicycling (even on an exercise bike) may be a more comfortable option. (22) In the Nurses’ Health Study II, for example, overweight women spent far less time walking briskly than normal weight women, but they spent about the same amount of time cycling.  If you don't like brisk walking or bicycling, any activity that makes your heart work harder will
help you meet the Physical Activity Guidelines for Americans, as long as you do it long enough and often enough. Walking and biking are also green ways to commute to work—good for the environment, and good for you.
to cover as many people as possible. In other words, they aren't right for everyone. How much exercise you need depends on your genes, your diet, how much muscle and fat you carry on your frame, how fit you are, and your capacity for exercise. A study of more 7,000 men who graduated from Harvard before 1950 suggests that older people, those who are out of shape, or those with disabilities may get as much benefit from 30 minutes of slower walking or other exercise as younger, more fit people get from the same amount of more-intense activity. (23)
In other words, if an exercise or physical activity feels hard, then it is probably doing your heart—and
the rest of you—some good, even if it doesn't fall into the "moderate" category. If you are currently not active at all, it may be daunting to start out with 30 minutes a day of activity, five days a week. So start with a shorter, less-intense bout of activity, and gradually increase over time until you can reach or exceed this goal. (1) This "start slow, build up over time" advice for physical activity applies to everyone, but it's especially true for older adults, (24) since starting slowly can help lower the risk of injury—and can make exercise more enjoyable. Read more about exercise safety.
Don't get stuck in a rut, though. As your body adapts to exercise, you'll need to push yourself more and more to get the same cardiovascular workout. Another way to know that it's time to pick up the pace is if you see your weight or waist size start creeping up on you.

The Bottom Line: Move More, Sit Less

Exercise is one of those rare things where the hype actually meets reality. Next to not smoking, getting regular physical activity is arguably the best thing you can do for your health. Any amount of exercise is better than none. The more you get, though, the better. And remember: Cutting back on television-watching and other sedentary pastimes is just as important as becoming more active.

References

1. U.S. Dept. of Health and Human Services. 2008 Physical Activity Guidelines for Americans. 2008.
2. Wang G, Pratt M, Macera CA, Zheng ZJ, Heath G. Physical activity, cardiovascular disease, and medical expenditures in U.S. adults. Ann Behav Med. 2004; 28:88-94.
3. Pratt M, Macera CA, Wang GJ. Higher direct medical costs associated with physical inactivity. Physician and Sportsmedicine. 2000; 28:63-70.
4. Owen N, Healy GN, Matthews CE, Dunstan DW. Too much sitting: the population health science of sedentary behavior. Exerc Sport Sci Rev. 2010; 38:105-13.
5. Hu FB, Li TY, Colditz GA, Willett WC, Manson JE. Television watching and other sedentary behaviors in relation to risk of obesity and type 2 diabetes mellitus in women. JAMA. 2003; 289:1785-91.
6. Dunstan DW, Barr EL, Healy GN, et al. Television viewing time and mortality: the Australian Diabetes, Obesity and Lifestyle Study (AusDiab). Circulation. 2010; 121:384-91.
7. Patel AV, Bernstein L, Deka A, et al. Leisure Time Spent Sitting in Relation to Total Mortality in a Prospective Cohort of US Adults. Am J Epidemiol. 2010.
8. Warren TY, Barry V, Hooker SP, Sui X, Church TS, Blair SN. Sedentary behaviors increase risk of cardiovascular disease mortality in men. Med Sci Sports Exerc. 2010; 42:879-85.
9. Manson JE, Hu FB, Rich-Edwards JW, et al. A prospective study of walking as compared with vigorous exercise in the prevention of coronary heart disease in women. N Engl J Med. 1999; 341:650-8.
10. Hu FB, Sigal RJ, Rich-Edwards JW, et al. Walking compared with vigorous physical activity and risk of type 2 diabetes in women: a prospective study. JAMA. 1999; 282:1433-9.
11. Tanasescu M, Leitzmann MF, Rimm EB, Willett WC, Stampfer MJ, Hu FB. Exercise type and intensity in relation to coronary heart disease in men. JAMA. 2002; 288:1994-2000.
12. Lee IM, Rexrode KM, Cook NR, Manson JE, Buring JE. Physical activity and coronary heart disease in women: is "no pain, no gain" passé? JAMA. 2001; 285:1447-54.
13. Sesso HD, Paffenbarger RS, Jr., Lee IM. Physical activity and coronary heart disease in men: The Harvard Alumni Health Study. Circulation. 2000; 102:975-80.
14. Gregg EW, Gerzoff RB, Caspersen CJ, Williamson DF, Narayan KM. Relationship of walki

ing to mortality among US adults with diabetes. Arch Intern Med. 2003; 163:1440-7.  15. Manson JE, Greenland P, LaCroix AZ, et al. Walking compared with vigorous exercise for the prevention of cardiovascular events in women. N Engl J Med. 2002; 347:716-25.
16. Hakim AA, Curb JD, Petrovitch H, et al. Effects of walking on coronary heart disease in elderly men: the Honolulu Heart Program. Circulation. 1999; 100:9-13.
17. Krishnan S, Rosenberg L, Palmer JR. Physical activity and television watching in relation to risk of type 2 diabetes: the Black Women's Health Study. Am J Epidemiol. 2009; 169:428-34.
18. Oguma Y, Shinoda-Tagawa T. Physical activity decreases cardiovascular disease risk in women: review and meta-analysis. Am J Prev Med. 2004; 26:407-18.
19. Jeon CY, Lokken RP, Hu FB, van Dam RM. Physical activity of moderate intensity and risk of type 2 diabetes: a systematic review. Diabetes Care. 2007; 30:744-52.
20. Mekary RA, Feskanich D, Malspeis S, Hu FB, Willett WC, Field AE. Physical activity patterns and
prevention of weight gain in premenopausal women. Int J Obes (Lond). 2009; 33:1039-47.  21. Mekary RA, Feskanich D, Hu FB, Willett WC, Field AE. Physical activity in relation to long-term weight maintenance after intentional weight loss in premenopausal women. Obesity (Silver Spring). 2010; 18:167-74.
22. Lusk AC, Mekary RA, Feskanich D, Willett WC. Bicycle riding, walking, and weight gain in premenopausal women. Arch Intern Med. 2010; 170:1050-6.
23. Lee IM, Sesso HD, Oguma Y, Paffenbarger RS, Jr. Relative intensity of physical activity and risk of coronary heart disease. Circulation. 2003; 107:1110-6.
24. Nelson ME, Rejeski WJ, Blair SN, et al. Physical activity and public health in older adults: recommendation from the American College of Sports Medicine and the American Heart Association. Circulation. 2007; 116:1094-105.
25. National Center for Health Statistics. Health, United States, 2009: With Chartbook on Trends in the Health of Americans. Hyattsville, MD, 2009.
26. Troiano RP, Berrigan D, Dodd KW, Masse LC, Tilert T, McDowell M. Physical activity in the United States measured by accelerometer. Med Sci Sports Exerc. 2008; 40:181-8.

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