The evidence of a strong inverse relationship between physical activity and risk of colon cancer seems unequivocal enough to justify the public health message that modest increases in physical activity of the population will help reduce the incidence of colon cancer.
The risk of endometrial cancer is associated with increased weight and body size (27). There are several case-control studies showing that inactivity is associated with an increased risk of endometrial cancer even when BMI is taken into account (Table 3). However, confounding by diet and other factors hamper the interpretation of these data.
Overweight is a risk factor for prostate cancer. The findings concerning the role of physical activity are controversial. Some case-control (97) and cohort studies (26,78) in which allowance has been made for BMI show no relationship between physical activity and prostate cancer, whereas some cohort studies (1,48,67) show a protective effect. A protective effect of exercise against benign prostatic hyperplasia has been observed in the U.S. Health Professionals Study, but the results were not controlled for weight (70).
Most epidemiological studies of cancer, obesity, and physical activity to date are beset with major methodological weaknesses, including problems in assessing physical activity and inadequate control of confounding factors. Because of the complex interrelationships between lifestyle variables, large long-term cohort studies are needed with careful designs, including proper definition and size of the study population, maintenance of high response rates, and improved and standardized methods of measuring factors linked to lifestyle and behavior.
It is not known whether the type, intensity, and timing in life cycle are important determinants of the protective effect of physical activity. There is a need for better assessment of the mode, intensity, and timing of physical activity in both observational and intervention studies.
There has been little research on the effects of physical activity and weight reduction on the progression of hormone-dependent cancers and colon cancer. Long-term RCT of exercise and dietary intervention in patients with these cancers are needed.
The protective effect of exercise against gallstones has been documented in the U.S. male population. Large-scale, high-quality epidemiological studies on well-defined patterns of physical activity (see section on research priorities in cancers) are needed to evaluate the effects of exercise in women and in other populations.
Also, RCT are needed to assess whether physical activity can prevent the formation of gallstones in obese people during and after weight reduction.
Some studies suggest that vigorous physical activity may predispose to osteoarthritis by the means of mechanical insult to the joint (9,16). An increased risk has been associated with strenuous sports (41) and with competitive but not recreational running (43). A beneficial effect of physical exercise in the prevention of osteoarthritis has not been demonstrated in any study thus far. Both physical exercise therapy (11) and weight reduction (58) may alleviate the symptoms of arthritis, but few studies have addressed the simultaneous effects of these modalities. One small uncontrolled study combining exercise with weight reduction (10) suggested that physical exercise may help preserve lean body mass during weight loss in obese patients with rheumatoid arthritis, but no effect of symptoms was observed in this study.
Obesity and low physical activity are among the proposed risk factors of low back pain, but the findings are controversial (30,49,100). While many RCT show therapeutic benefits of exercise (17,65,66) and deleterious effect of bed rest (55) in the treatment of back pain, the evidence of benefits of physical activity in back pain is equivocal (13,55).
The evidence of benefits of physical activity, beyond the effect on body weight regulation, in the prevention and treatment of osteoarthritis and back pain is inconclusive. Given the public health importance of these conditions and the theoretical benefits of weight control and physical exercise in these conditions, more research in this area is needed.
The research priorities concerning the role of physical activity in obesity-related musculosceletal disorders are as follows:
1. High-quality epidemiologic studies are needed to assess the preventive potential of physical activity and its various dimensions, including types of activity, intensity, duration, frequency, changes in activity levels over time for various chronic disease and functional end points, including arthritis and low back pain. These studies should be designed to take into account and explore the complex interrelationships between physical activity, body weight, lifestyle, diet, and health.
2. Intervention and observational studies of weight loss with various dimensions of physical activity as defined above in the progression of established osteoarthritis of the knee and hip are needed.
3. RCT to test the hypothesis that certain types of exercise would be beneficial during weight reduction in patients with osteoarthritis.
Obesity is associated with reproductive disorders including polycystic ovary syndrome, menstrual disorders, infertility, miscarriage, and pregnancy complications. These problems are ameliorated by weight reduction (64). We identified no studies that have specifically examined the relationship between these conditions and physical activity in obese patients.
RCT are needed to test whether exercise alone or combined with weight reduction by diet is effective in the treatment of sleep apnea in obese subjects and in normalizing reproductive abnormalities in obese women.
Obese persons often have limitations in psychological and physical well-being and in other aspects of the day-to-day life, often summarized under the multidimensional concept of health-related quality of life (HRQL) (29,75,86). Weight reduction appears to improve some dimensions of HRQL (76), but the few data are difficult to interpret, especially in less severe obesity (76).
RCT are needed to determine whether physical activity improves the various aspects of health-related quality of life beyond its effect of weight loss. Valid assessment of HRQL should be included in all intervention studies of obese persons.
Also, RCT are needed to study the effects of physical activity in binge eating disorder.
1. Albanes, D., A. Blair, and P. R. Taylor. Physical activity and risk of cancer in the NHANES I population. Am. J. Public Health 79: 744–750, 1989.
2. Ballard-Barbash, R., A. Schatzkin, D. Albanes, et al. Physical activity and risk of large bowel cancer in the Framingham Study. Cancer Res. 50: 3610–3613, 1990.
3. Basso, L, P. T. McCollum, M. R. Darling, A. Tocchi, and W. A. Yanner. A descriptive study of pregnant women with gallstones: relation to dietary and social habits, education, physical activity, height, and weight. Eur. J. Epidemiol. 8: 629–633, 1992.
4. Bernstein, L., B. E. Henderson, R. Hanisch, J. Sullivan-Halley, and R. K. Ross. Physical exercise and reduced risk of breast cancer in young women. J. Natl. Cancer Inst. 86: 1403–1408, 1994.
5. Cairney, J. and T. J. Wade. Correlates of body weight in the 1994 National Population Health Survey. Int. J. Obes. Relat. Metab. Disord. 22: 584–591, 1998.
6. Chen, C-L., E. White , K. E Malone, and J. R. Daling. Leisure-time physical activity in relation to breast cancer among young women (Washington, D.C.). Cancer Causes Control 8: 77–84, 1997.
7. Colditz, G. A., C. C. Cannuscio, and A. L. Frazier. Physical activity and reduced risk of colon cancer: implications for prevention. Cancer Causes Control 8: 649–667, 1997.
8. Coogan, P. F., P. A. Newcomb, R. W. Clapp, A. Trentham-Diez, J. A. Baron, and M. P. Longnecker. Physical activity in usual occupation and risk of breast cancer (United States). Cancer Causes Control 8: 626–631, 1997.
9. Cooper, C., H. Inskip, P. Croft, et al. Individual risk factors for hip osteoarthritis: obesity, hip injury, and physical activity. Am. J. Epidemiol. 147: 516–522, 1998.
10. Engelhart, M., J. Kondrup, L. H. Hoie, V. Andersen, J. H. Kristensen, and B. L. Heitmann. Weight reduction in obese patients with rheumatoid arthritis, with preservation of body cell mass and improved physical fitness. Clin. Exp. Rheumatol. 14: 289–293, 1998.
11. Ettinger, W. H., Jr., R. Burns, S. P. Messier, et al. A randomized trial comparing aerobic exercise and resistance exercise with a health education program in older adults with knee osteoarthritis: The Fitness Arthritis and Seniors Trial (FAST). JAMA 277: 25–31, 1997.
12. Everhart, J. E. Contributions of obesity and weight loss to gallstone disease. Ann. Intern Med. 119: 1029–1035, 1993.
13. Faas, A., J. T. van Eijk, A. W. Chavannes, and J. W. Gubbels. A randomized trial of exercise therapy in patients with acute low back pain: efficacy on sickness absence. Spine 20: 941–947, 1995.
14. Felson, D. T., J. J. Anderson, A. Naimark, A. M. Walker, and R. F. Meenan. Obesity and knee osteoarthritis. Ann. Intern. Med. 109: 18–24, 1988.
15. Felson, D. T., Y. Zhang, J. M. Anthony, A. Naimark, and J. J. Anderson. Weight loss reduces the risk for symptomatic knee osteoarthritis in women. Ann. Intern. Med. 116: 535–539, 1992.
16. Felson, D. T., Y. Zhang, M. T. Hannan, et al. Risk factors for incident radiographic knee osteoarthritis in the elderly: the Framingham Study. Arthritis Rheum. 40: 728–733, 1997.
17. Ferrell, B. A., K. R. Josephson, A. M. Pollan, S. Loy, and B. R. Ferrell. A randomized trial of walking versus methods for chronic pain management. Aging 9: 99–105, 1997.
18. Fraser, G. E. and D. Shavlik. Risk factors, lifetime risk, and age at onset of breast cancer. Ann. Epidemiol. 7: 375–382, 1997.
19. Friedenreich, C. M. and T. E. Rohan. Physical activity and risk of breast cancer. Eur. J. Cancer Prev. 4: 145–151, 1995.
20. Friedman, G. D., W. B. Kannel, and T. R. Dawber. The epidemiology of gallbladder disease: observations in the Framingham Study. J. Chronic Dis. 19: 273–292, 1966.
21. Frisch, R. E., G. Wyshak, N. L. Albright, et al. Lower prevalence of breast cancer and cancers of reproductive system among former college athletes compared to nonathletes. Br. J. Cancer 52: 885–891, 1985.
22. Galletly, C., A. Clark, L. Tomlinson, and F. Blaney. A group program for obese, infertile women: weight loss and improved psychological health. J. Psychosom. Obstet. Gynaecol. 17: 125–128, 1996.
23. Gammon, M. D., J. B. Schoenberg, J. A. Britton, et al. Recreational physical activity and breast cancer risk among women under age 45 years. Am. J. Epidemiol. 147: 273–280, 1998.
24. Gerhardsson de Verdier, M., G. Steineck, U. Magman, A. Rieger, and S. Norrell. Physical activity and colon cancer: a case-referent study in Stockholm. Int. J. Cancer
25. Giovannucci, E., A. Ascherio, E. B. Rimm, G. A. Golditz, M. J. Stampfer, and W. C. Willet. Physical activity, obesity, and risk of colon cancer and adenoma in men. Ann. Intern. Med. 122: 327–234, 1995.
26. Giovannucci, E., M. Leitzmann, D. Spiegelman, et al. A prospective study of physical activity and prostate cancer in male health professionals. Cancer Res. 58: 5117–5122, 1998.
27. Goodman, M. T., J. H. Hankin, L. R. Wilkens, et al. Diet, body size, physical activity, and the risk of endometrial cancer. Cancer Res. 57: 5077–5085, 1997.
28. Grimm, R. H., Jr., G. A. Granditis, J. A. Cutler, et al. Relationships of quality-of-life measures to long-term lifestyle and drug treatment in the Treatment of Mild Hypertension Study. Arch. Intern. Med. 157: 638–648, 1997.
29. Han, T. S., M. A. R. Tijhuis, M. E. J. Lean, and J. Seidell. Quality of life in relation to overweight and body fat distribution. Am. J. Health 88: 1814–1820, 1998.
30. Heistaro, S., E. Vartiainen, M. Heliövaara, and P. Puska. Trends in back pain in eastern Finland, 1972–1992, in relation to socioeconomic status and behavioral risk factors. Am. J. Epidemiol. 148: 671–682, 1998.
31. Hirose K., K. Tajima, N. Hamajima, et al. Sub-site (cervix/endometrium)-specific risk and protective factors in uterus cancer. Jpn. J. Cancer Res. 87: 1001–1009, 1996.
32. Hirose, K., K. Tajima, N. Hamajima, et al. A large-scale, hospital based case-control study of risk factors of breast cancer according to menopausal status. Jpn. J. Cancer Res. 86: 146–154, 1995.
33. Hsing, A. W., J. McLaughlin, W-H. Chow, et al. Risk factors for colorectal cancer in a prospective study among U.S. white men. Int. J. Cancer 77: 549–553, 1998.
34. Hu, Y-H., C. Nagata, H. Shimizu, N. Kaneda, and Y. Kashiki. Association of body mass index, physical activity, and reproductive histories with breast cancer: a case-control study in Gifu, Japan. Breast Cancer Res. Treat. 43: 65–72, 1997.
35. Huang, Z., S. E. Hankinson, G. A. Colditz, et al. Dual effects of weight and weight gain on breast cancer risk. JAMA 5: 278: 1407–1411, 1997.
36. Hunter, D. J. and W. C. Willett. Diet, body size, and breast cancer. Epidemiol. Rev. 15: 110–132, 1993.
37. Jorgensen, T, L. Kay, and K. Schultz-Larsen. The epidemiology of gallstones in a 70-year-old Danish population. Scand. J. Gastroenterol. 25: 335–340, 1990.
38. Jorgensen, T. Gallstones in Danish population: relation to weight, physical activity, smoking, coffee consumption, and diabetes mellitus. Gut 30: 528–534, 1989.
39. Kato, I, A. Nomura, G. N. Stemmermann , and P. H Chyou. Prospective study of clinical gallbladder disease and its association with obesity, physical activity, and other factors. Dig. Dis. Sci.
37: 784–790, 1992.
40. Kono, S., K. Shinchi, I. Todoroki, et al. Gallstone disease among Japanese men in relation to obesity, glucose intolerance, exercise, alcohol use, and smoking. Scand. J. Gastroenterol. 30: 372–376, 1995.
41. Kujala, U. M., S. Taimela, T. Viljanen, et al. Physical loading and performance as predictors of back pain in healthy adults: a 5-year prospective study. Eur. J. Appl. Physiol. 73: 452–458, 1996.
42. Kune, G., S. Kune, and L. Watson. Body weight and physical activity as predictors of colorectal cancer risk. Nutr. Cancer 13: 9–17, 1990.
43. Lane, N. E. Physical activity at leisure and risk of osteoarthritis. Ann. Rheum. Dis. 55: 682–684, 1996.
44. Latikka, P. Relationship of physical activity and breast cancer: an epidemiological perspective. Sports Med. 26: 133–143, 1998.
45. Lavie, C. J. and R. V. Milani. Effects of rehabilitation, exercise training, and weight reduction on exercise capacity, coronary risk factors, behavioral characteristics, and quality of life in obese coronary patients. Am. J. Cardiol. 79: 397–401, 1997.
46. Le Marchand, L., L. R. Wilkens, L. N. Kolonel, J. H. Hankin, and L.-C. Lyu. Associations of sedentary lifestyle, obesity, smoking, alcohol use, and diabetes with the risk of colorectal cancer. Cancer Res. 57: 4787–4794, 1997.
47. Lee, I. M., J. Manson, U. Ajani , R, Paffenbarger, C. Hennekens, and J. Buriog. Physical activity and risk of colon cancer: The Physicians’ Health Study. Cancer Causes Control 8:568–574, 1997.
48. Lee, I. M., R. S. Paffenbarger Jr., and C. C. Hsieh. Physical activity and risk of prostatic cancer among college alumni. Am. J. Epidemiol. 135: 169–175, 1992.
49. Leino, P. I. Does leisure time physical activity prevent low back disorders? A prospective study of metal industry employees. Spine
18: 863–871, 1993.
50. Leitzmann, M. F., E. L. Giovanucci, E. B. Rimm, et al. The relation of physical activity to risk for symptomatic gallstone disease in men. Ann. Int. Med. 128: 417–425, 1998.
51. Levi, F., C. La Vecchia, E. Negri, and S. Franceschi. Selected physical activities and the risk of endometrial cancer. Br. J. Cancer 67: 846–851, 1993.
52. Levine M. D., M. D. Marcus, and P. Moulton. Exercise in the treatment of binge eating disorder. Int. J. Eat. Dis. 19: 171–177, 1996.
53. Longnecker, M., M. Gerhardsson de Verdier, H. Fromkin, and C. Carpenter. A case-control study of physical activity in relation to risk of cancer of the right colon and rectum. Int. J. Epidemiol.
24: 42–50, 1995.
54. Maclure, K. M., K. C. Hayes, G. A. Colditz, M. J. Stampfer, F. E. Speizer, and W. C. Willett. Weight, diet, and the risk of symptomatic gallstones in middle-aged women. N. Engl. J. Med. 321: 563–569, 1989.
55. Malmivaara, A., U. Hakkinen, T. Aro, et al. The treatment of acute low back pain: bed rest, exercises, or ordinary activity? N. Engl. J. Med.
332: 351–355, 1995.
56. Manninen P., H. Riihimäki, M. Heliövaara, and P. Mäkelä. Overweight, gender and knee osteoarthritis. Int. J. Obes. Relat. Metab. Disord. 20: 595–597, 1996.
57. Martinez, M. E., E. Giovanucci, D. Spiegelmann, D. J. Hunter, W. C. Willett, and G. A. Colditz. Leisure-time physical activity, body size, and colon cancer in women. Nurses’ Health Study Research Group. J. Natl. Cancer Inst.
89: 948–955, 1997.
58. McGoye, B. V., M. Deitel, R. J. Saplus, and M. E. Kliman. Effect of weight loss on musculoskeletal pain in the morbidly obese. J. Bone Joint Surg. (Br.) 72: 322–323, 1990.
59. McTiernan, A., J. L. Stanford, N. S. Weiss, J. R. Daling, and L. F. Voigt. Occurrence of breast cancer in relation to recreational exercise in woman aged 50–64 years. Epidemiology 7: 598–604, 1996.
60. Mezzetti, M., C. La Vecchia, A. Decarli, P. Boyle, R. Talamini, and S. Franceschi. Population attributable risk for breast cancer: diet, nutrition, and physical exercise. J. Natl. Cancer Inst. 90: 389–394, 1998.
61. Moerman, C. J., M. P. H. Berns, F. W. M. Smeets, and D. Kromhout. Regional fat distribution as risk factor for clinically diagnosed gallstones in middle-aged men: a 25-year follow-up study (the Zutphen Study). Int. J. Obes. 18: 435–439, 1994.
62. Moradi, T., O. Nyrén, R. Bergström, et al. Risk for endometrial cancer in relation to occupational physical activity: a nationwide cohort study in Sweden. Int. J. Cancer 76: 665–670, 1998.
63. Netzer, N., W. Lormes, V. Giebelhaus, et al. Köperliches Training bei Patienten mit Schlafapnoe. Pneumonologie 51: 779–782, 1997.
64. Norman, R. J. and A. M. Clark. Obesity and reproductive disorders: a review. Reprod. Fertil. Dev. 10: 55–63, 1998.
65. O’Sullivan, P. B., L. Twomey, and G. T. Allison. Altered abdominal muscle recruitment in patients with chronic back pain following a specific exercise. J. Orthop. Sports Phys. Ther. 27: 114–124, 1998.
66. O’Sullivan, P. B., G. T. Phyty, L. Twomey, and G. T. Allison. Evaluation of specific stabilizing exercise in the treatment of chronic low back pain with radiologic diagnosis of spondylolysis or spondylolisthesis. Spine 22: 2959–2967, 1998.
67. Oliveria, S. A., H. W. Kohl III, D. Trichopoulos, and S. N. Blair. The association between cardiorespiratory fitness and prostate cancer. Med. Sci. Sports Exerc. 28: 97–104, 1996.
68. Ortega, R. M., M. Fernandez-Azuela, A. Encinas-Sotillos, P. Andreas, and A. M. Lopez-Sobaler. Differences in diet and food habits between patients with gallstones and controls. J. Am. Coll. Nutr. 16: 88–95, 1997.
69. Paffenbarger, R. S., Jr., I.-M. Lee, and A. L. Wing. The influence of physical activity on the incidence of site-specific cancers in college alumni. Exercise, Calories, Fat, and Cancer, M. M. Jacobs (Ed.). New York: Plenum Press, 1992, pp. 7–15.
70. Platz, E. A., I. Kawachi, E. B. Rimm, et al. Physical activity and benign prostatic hyperplasia. Arch. Intern. Med. 158: 2349–2356, 1998.
71. Rejeski, W. J., L. R. Brawley, and S. A. Shumaker. Physical activity and health-related quality of life. Exerc. Sport. Rev. 24: 71–108, 1996.
72. Rippe, J. M., J. M. Price, S. A. Hess, et al. Improved psychological well-being, quality of life, and health practices in moderately overweight women participating in a 12-week structured weight loss program. Obes. Res. 6: 208–218, 1998.
73. Sahi, T., R. S. Paffenbarger, Jr., C. Hsieh, and I.-M. Lee. Body mass index, cigarette smoking, and other characteristics as predictors of self-reported, physician-diagnosed gallbladder disease in male college alumni. Am. J. Epidemiol. 147: 644–651, 1998.
74. Sarin, S. K, B. M. Kapur, and R. K. Tandon. Cholesterol and pigment gallstones in northern India: a prospective analysis. Dig. Dis. Sci.
75. Sarles, M, C. Chabert, Y. Pommeau, E. Save, H. Mouret, and A. Gerolaml. Diet and cholesterol gallstones: a study of 101 patients with cholelithiasis compared to 101 matched controls. Am. J. Dig. Dis. 14: 531–537, 1996.
76. Sarlio-Lähteenkorva, S., A. Stunkard, and A. Rissanen. Psychosocial factors and quality of life in obesity. Int. J. Obes. Relat. Metab. Disord. 19(Suppl. 6): S1-S5, 1995.
77. Sesso, H. D. , R. S Paffenbarger, Jr., and I.-M. Lee. Physical activity and breast cancer risk in the college alumni health study (United States). Cancer Causes Control
9: 433–439, 1998.
78. Shephard, R. J., and P. N. Phek. Association between physical activity and susceptibility to cancer: possible mechanisms. Sports Med. 26: 293–315, 1998.
79. Shikey, M. Body weight and colon cancer. Am. J. Clin. Nutr. 63(Suppl.1): 442S-444S, 1996.
80. Slattery, M., N. Abd-Elghany, R. Kerber, and M. Schumacher. Physical activity and colon cancer: a comparison of various indicators of physical activity to evaluate the association. Epidemiology 1: 481–485, 1990.
81. Slattery, M. L., M. C. Schumacher, K. R. Smith, D. W. West, and N. Abd-Elghany. Physical activity, diet, and risk of colon cancer in Utah. Am. J. Epidemiol. 128: 989–99, 1988.
82. Slattery, M., J. Potter, B. Caan, et al. Energy balance and colon cancer-beyond physical activity. Cancer Res. 57: 75–80, 1997.
83. Steenland, K., S. Nowlin, and S. Palu. Cancer incidence in the National Health and Nutrition survey. I. follow-up data: diabetes, cholesterol, pulse, and physical activity. Cancer Epidemiol. Biomark. Prev. 4:807–811, 1995.
84. Stewart, A. L., R. D. Hays, K. B. Wells, W. H. Rogers, K.L. Spritzer, and S. Greenfield. Long-term functioning and well-being outcomes associated with physical activity and exercise in patients with chronic conditions in the Medical Outcomes Study. J. Clin. Epidemiol. 47: 719–730, 1994.
85. Sturgeon, S. R., L. A. Brinton, M. L. Berman, et al. Past and present physical activity and endometrial cancer risk. Br. J. Cancer 68: 584–589, 1993.
86. Sullivan, M., J. Karlsson, L. Sjöström, et al. Swedish obese subjects (SOS): an intervention study of obesity: baseline evaluation of health and psychosocial functioning in the first 1743 subjects examined. Int. J. Obes. Relat. Metab. Disord. 17: 503–512, 1993.
87. Suratt, P. M., R. F. McTier, L. J. Flinley, S. L. Pohl, and S. C. Wilhoit. Effect of very low calorie diets with weight loss on obstructive sleep apnea. Am. J. Clin. Nutr. 56: 182S-184S, 1992.
88. Taioli, E., J. Barone, and E. L. Wynder. A case-control study on breast cancer and body mass. Eur. J. Cancer 31A: 723–728, 1995.
89. The Rome Group for Epidemiology and Prevention of Cholelithiasis (GREPCO). The epidemiology of gallstone disease in Rome, Italy: Part II. factors associated with the disease. Hepatology
90. Thun, M. J., E. E. Calle, M. M. Namboodiri, et al. Risk factors for fatal colon cancer in a large prospective study. J. Natl. Cancer Inst. 84: 1491–1500, 1992.
91. Thune, I. and E. Lund. Physical activity and the risk of prostate and testicular cancer: a cohort study of 53,000 Norwegian men. Cancer Causes Control 5: 549–556, 1994.
92. Thune, I. and E. Lund. Physical activity and risk of colorectal cancer in men and women. Br. J. Cancer 73: 1134–1140, 1996.
93. Thune, I., T. Brenn, E. Lund, and M. Gaard. Physical activity and the risk of breast cancer. N. Engl. J. Med. 336: 1269–1275, 1997.
94. Utter, A. and F. Goss. Exercise and gallbladder function. Sports Med. 23: 218–227, 1997.
95. Verbrugge, L. M., D. M. Gates, and R. W. Ike. Risk factors for disability among US adults with arthritis. J. Clin. Epidemiol. 44: 167–182, 1991.
96. Wheeler, M., L. L. Hills, and B. Laby. Cholelithiasis: a clinical and dietary survey. Gut. 11: 430–437, 1970.
97. Whittemore, A. S., L. N. Kolonel, A. H. Wu, et al. Prostate cancer in relation to diet, physical activity, and body size in blacks, whites, and Asians in the United States and Canada. J. Natl. Cancer. Inst. 87: 652–661, 1995.
98. Will, J. C., D. A. Galuska, F. Vinicor, and E. E. Calle. Colorectal cancer: another complication of diabetus mellitus? Am. J. Epidemiol. 147: 816–825, 1998.
99. Williams, C. N. and J. L. Johnston. Prevalence of gallstones and risk factors in Caucasian women in a rural Canadian community. Can. Med. Assoc. J. 122: 664–668, 1980.
100. Wright, D., S. Barrow, A. D. Fisher, S. D. Horsley, and M. I. V. Jayson. Influence of physical, psychological and behavioural factors on consultations for back pain. Br. J. Rheumatol. 34: 156–161, 1995.
101. Yong, T., M. Palta, J. Dempsey, J. Skatrud, S. Weber, and S. Badr. The occurrence of sleep-disordered breathing among middle-aged adults. N. Engl. J. Med. 328: 1230–1235, 1993.
102. Zheng, W., X. O. Shu, J. K. McLaughlin, W. H. Chow, Y. T. Gayo, and W. J. Blot. Occupational physical activity and incidence of cancers of breast, corpus uteri, and ovary in Shanghai. Cancer 71: 3620–3624, 1993.
103. Ziegler, R. G. Anthropometry and breast cancer. J. Nutr. 127 (5 Suppl.): 924S-928S, 1997.