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3 Physical Activity, Obesity, and Weight Management The effects of physical activity have been investigated in relation to weight loss, weight loss maintenance, and the prevention of weight gain. This workshop session included a presentation on those topics followed by a discussion period. This chapter includes a review of the evidence on effects of physical activity in weight management; a brief discussion of aging, inactivity, and obesity; additional information from epidemiologi- cal studies; and a brief summary of major points raised during the group discussion. EFFECTS OF PHYSICAL ACTIVITY ON WEIGHT LOSS, WEIGHT LOSS MAINTENANCE, AND THE PREVENTION OF WEIGHT GAIN Presenter: Joseph E. Donnelly This presentation provided background information on physical ac- tivity and weight management, and also addressed various types of evi- dence related to physical activity for weight loss and for the prevention of weight gain. Background The general concept of physical activity and weight management is straightforward: 59
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60 PHYSICAL ACTIVITY WORKSHOP • Physical activity expends energy • Energy expenditure can produce a negative energy balance • Weight loss occurs during a negative energy balance Many compensatory mechanisms can occur, however, when one in- creases physical activity. These include changes in diet, spontaneous ac- tivity, resting metabolism, and others. Thus an important question is how to create an energy gap that is effective for weight management (includ- ing weight maintenance or weight loss). Evidence that Physical Activity Will Alter Energy Balance and Provide Weight Loss Many population studies show that measures of body fat status are lower among those with higher physical activity levels. For example, using data from a population survey, Holcomb et al. (2004) showed that body mass index (BMI), percentage body fat, and waist-to-hip ratio each decreased with an increasing level of physical activity. A number of meta-analyses have shown that the amount of weight lost with increases in physical activity tends to be small, and it is greater for men than for women. Ballor and Keesey (1991) conducted a meta- analysis of exercise and weight loss that included 53 studies. With an energy expenditure of nearly 1,500 kilocalories (kcal) per week from exercise for men, their mean weight loss was approximately 1.4 kilo- grams (kg) after approximately 16 weeks. The women had a mean en- ergy expenditure of more than 900 kcal per week from exercise, and their mean weight loss was less than 1 kg after about 11 weeks. A similar meta-analysis by Garrow and Summerbell (1994) covering eight random- ized controlled trials (five for men and three for women) found slightly greater weight loss, but the results were very similar. Does an exercise intervention alone lead to weight loss? Studies of Targeted Risk Reduction Interventions through Defined Exercise (STRRIDE) examined this question in an 8-month randomized controlled trial of overweight untrained adults (Slentz et al., 2004). The investiga- tors treated overweight persons with three different levels of exercise but instructed them not to change their diet. The control group gained about 1 kg; the low-amount, moderate-intensity exercise group (equivalent to walking approximately 12 miles/week) and the low-amount, vigorous- intensity exercise group (equivalent to jogging approximately 12
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61 OBESITY AND WEIGHT MANAGEMENT miles/week) lost about 1 kg. The high-amount, vigorous-intensity exer- cise group (equivalent to jogging approximately 20 miles/week) lost about 3.5 kg on average—4 percent of their body weight. This latter amount approaches clinical significance with regard to health benefits. Slentz et al. (2004) examined weight change per mile of exercise and estimated that covering a distance of about 6 miles/week corresponds with the amount of exercise that results in weight maintenance. In a supervised study in which subjects came into the laboratory, Ross and colleagues (2000, 2004) found that a 500- to 700-kcal deficit per day, either through diet or exercise, produced a 6.5 percent weight loss for women and an 8 percent weight loss for men over a 12-week period. In the 16-month, supervised Midwest Exercise Trial, Donnelly et al. (2003) found, using objective measures, that the men expended approxi- mately 300 kcal more per session than did the women when prescribed the same relative amount of exercise in terms of frequency, intensity, and duration. With ad libitum eating, the men lost, on average, about 5 per- cent of their baseline weight within about 9 months. In contrast, the women did not lose weight; however, they gained little or no weight on average over the 16 months. Individual variation was substantial, espe- cially for the women. All but one of the men in the Midwest Exercise Trial lost weight, in varying amounts, but only half of the women lost weight. As also discussed later in the session by Dr. Glenn Gaesser, other studies have produced the results illustrated in Figure 3-1. Evidence that Physical Activity Will Benefit Weight Maintenance Among Persons Who Have Lost Weight Qualitative evidence from the National Weight Control Registry (Klem et al., 1997) suggests that the levels of physical activity required to maintain weight following a substantial weight loss are higher than many people realize—more than 2,500 kcal/week. Weight management programs suggest that approximately 300 minutes of exercise are needed per week to produce weight maintenance for one year (LeCheminant et al., 2005).
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62 PHYSICAL ACTIVITY WORKSHOP 10 Gainers (N = 11) Change in body fat (kg) 5 0 –5 Losers (N = 20) –10 Subjects FIGURE 3-1 Individual variation in body fat mass change in response to aero- bic exercise training in obese women. SOURCE: Lamarche et al. (1992). Reprinted from Metabolism 41(11), La- marche et al., Is body fat loss a determinant factor in the improvement of carbo- hydrate and lipid metabolism following aerobic exercise training in obese women? Pp. 1249–1256, 1992, with permission from Elsevier. A dose–response effect was demonstrated in a study by Jakicic et al. (1999). After weight loss at 6 months, weight was maintained for 6 months by those exercising more than 200 minutes per week, whereas those exercising less than 150 minutes per week experienced regain of weight. More recent work by Jakicic and colleagues (John M. Jakicic, University of Pittsburgh, personal communication, October 16, 2006) indicates that physical activity levels were substantially higher for those who maintained a weight loss of at least 10 percent of their body weight for 18 months than for those who did not maintain that degree of weight loss. Dr. Donnelly indicated that the randomization in most studies is done at baseline. However, randomization after weight loss is the correct study design but is rarely used. Jeffery et al. (2003) randomized subjects at baseline and at the beginning of the period of testing interventions to maintain weight. Subjects randomized to the 2,500 kcal/week exercise group maintained weight better, on average, than did those in the 1,000 kcal/week exercise group (Figure 3-2). Although there was considerable
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63 OBESITY AND WEIGHT MANAGEMENT variation in exercise levels, the subjects who were asked to do more ex- ercise did more exercise. In a study by Borg et al. (2002) in which men were randomized after weight loss either to control or exercise groups for 6 months, a physical activity energy expenditure of approximately 2,400 kcal/week was asso- ciated with the maintenance of weight loss. Three additional studies were found in which subjects were random- ized after weight loss. In the study by Perri et al. (1988), all groups did better than the controls; but the groups assigned to behavior plus exercise did no better than the behavioral groups at 18 months. Leermakers and colleagues (1999) found that after 6 months, weight regain was lower among the exercise plus behavioral strategies group than among the group with exercise but no behavioral strategies. A somewhat con- founded 24-month study by Fogelholm et al. (2000) found less weight regain among those in the 1,000 kcal/week exercise group than in the Baseline 6 months 12 months 18 months 0 -5 -10 Pounds -15 -20 1,000 kcal 2,500 kcal -25 FIGURE 3-2 Mean weight change over time by treatment group. NOTES: ♦ = standard behavior therapy (SBT) group with a goal of expending 1,000 extra kilocalories per week; ■ = high physical activity (HPA) treatment group with a goal of expending 2,500 extra kilocalories per week. SBT group marginally different from the HPA group at 12 months (p = .07) and signifi- cantly different at 18 months (p = .04). SOURCE: Jeffery et al. (2003). Adapted, with permission, from The American Journal of Clinical Nutrition.
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64 PHYSICAL ACTIVITY WORKSHOP control group. There was no difference, however, between the 2,000 kcal/week exercise group and the controls, perhaps suggesting attrition problems. This suggests a benefit–risk question: Is it better to get a lower level of exercise for many years or a higher level of exercise with the risk of greater attrition? Evidence on Physical Activity in the Prevention of Weight Gain Dr. Donnelly presented evidence to support his position that rela- tively small amounts of physical activity may be sufficient to enable people to prevent unhealthy weight gain. Some investigators suggest that people gain weight in episodes related to life events such as marriage and having children, and others use a more linear perspective. Hill et al. (2003), for example, using data from the National Health and Nutrition Examination Survey and from the Coronary Artery Risk Development in Young Adults study, concluded that the energy gap for approximately 50 percent of the population may be as small as 15 kcal/day, and that speci- fying a gap of 50 kcal/day would cover about 90 percent of the popula- tion. Hill uses a value of 100 kcal/day to represent the energy gap, but it is acknowledged that currently there is little experimental data to support this value. In an 18-month study with middle-aged women, Donnelly et al. (2000) showed that either 30 minutes of supervised continuous exercise three times a week or two 10- to 15-minute bouts of supervised exercise 5 days per week prevented weight gain without a dietary intervention. Dunn et al. (1999) found that sedentary men and women randomized either to lifestyle or structured exercise groups, with a goal of 1,000 kcal of energy expenditure per week, gained little or no weight in the 2-year intervention period.1 In an ongoing study (John M. Jakicic, University of Pittsburgh, per- sonal communication, October 16, 2006), preliminary data show that after 18 months, subjects assigned to either 150 minutes or 300 minutes of physical activity per week weighed about 1 kilogram less than at base- line. If confirmed, this finding suggests that small amounts of physical activity may be sufficient to maintain the weight of persons who have not recently undergone a period of weight loss. 1 Dr. Blair noted later that actual energy expenditure was only about 65 kcal/day.
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65 OBESITY AND WEIGHT MANAGEMENT Concluding Remarks Physical activity or weight loss creates a relatively small energy gap and cannot be expected to provide the weight loss that is seen with en- ergy restriction. Effects appear to differ for men and women, and there are responders and nonresponders. Dr. Donnelly took the position that the time and amount of energy expenditure required for the prevention of unhealthy weight gain appears to be 15 to 30 minutes/day or about 700 to 1,000 kcal/week. The amount of physical activity needed to achieve the loss of 5 percent of one’s body weight appears to be about 45 min- utes/day or 2,000 to 2,500 kcal/week. For weight-loss maintenance, the amount of physical activity required is likely to be similar to, or perhaps greater than, that for weight loss. DISCUSSION Aging, Inactivity, and Obesity Discussant: Andrew Goldberg Predictors of obesity and weight regain include high caloric intake, physical inactivity, low resting metabolic rate, low fat oxidation, reduced muscle mass, aging, decreased insulin sensitivity, and perhaps elevated adipose lipoprotein lipase activity (Ravussin and Swinburn, 1993). Aging is associated with a decline in energy expenditure, which when not com- pensated by a reduction in caloric intake, leads to weight gain. Regular physical activity will increase energy expenditure for older people. Main- taining energy balance with aging is critical to prevent obesity and weight regain following successful weight loss. Studies in postmenopausal women by Goldberg and colleagues (Nicklas et al., 1996) show that weight loss, when combined with exer- cise training, blunts the decline in resting metabolic rate and in fat oxidation observed with weight loss alone. Dr. Goldberg’s group has shown that weight loss plus an increase in VO2max of greater than 5 per- cent results in several health benefits, including reductions in intra- abdominal fat and insulin resistance; improvements in glucose tolerance, insulin sensitivity, and blood pressure; reductions in total and low density lipoprotein cholesterol and triglycerides; and increases in high density lipoprotein cholesterol (Lynch et al., 2001).
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66 PHYSICAL ACTIVITY WORKSHOP A study by Bunyard et al. (1998) shows that both obese and lean sedentary middle-aged men were able to increase their exercise capacity by 15 percent with an aerobic exercise program. The lean sedentary group lost about 1.8 kg after 6 months of training despite increasing their caloric intake, and the obese sedentary men lost about 8 kg after 6 months of the exercise training plus hypocaloric weight loss instruction. Master athletes who discontinued exercise training for 8 weeks experi- enced a reduction in VO2max of about 15 percent and gained about 0.5 kg, despite reducing their caloric intake by 17 percent. All groups con- verged to about the same level of fitness, but when placed on isocaloric weight maintaining diets, the obese and lean men were able to consume 5 percent and 8 percent more calories, respectively, without gaining weight. These results provide evidence that sedentary older people can change their daily exercise habits to increase their energy expenditure from physical activity, allowing them to eat more without gaining weight. Thus regular aerobic exercise, by increasing daily energy expen- diture, may counter the age-related tendency toward obesity and its asso- ciated cardiovascular risk factors. Preliminary studies are in progress in Dr. Goldberg’s laboratory to test the hypothesis that weight loss, when combined with aerobic exer- cise training, will maintain both the resting metabolic rate and the oxida- tion of fat and carbohydrate, with subsequent cardiometabolic and weight maintenance benefits (Ortmeyer et al., 2006). This hypothesis is illus- trated in Figure 3-3. Our understanding of the potential benefits of exer- cise training for weight management in obese middle-aged and older people may be enhanced by knowledge of the metabolic mechanisms by which exercise, when combined with weight loss, increases fat and car- bohydrate oxidation in muscle.
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67 OBESITY AND WEIGHT MANAGEMENT Weight Loss Weight Loss + Exercise RMR RMR Fat and CHO OX Fat and CHO OX LPL LPL LPL LPL CPT-1 CPT-1 GS GS Insulin sensitivity (M) Insulin sensitivity (M) Lipid partitioning/utilization Lipid partitioning/utilization Cardiometabolic benefit Cardiometabolic benefit Weight regain Weight regain FIGURE 3-3 Hypothesis: Metabolic adaptations to weight loss with or without aerobic exercise. NOTE: RMR=resting metabolic rate; CHO=carbohydrate; OX=oxidation; LPL=lipoprotein lipase; CPT-1=carnitine palmitoyltransferase-1; GS=glycogen synthase. SOURCE: Goldberg (2006). Additional Epidemiological Data on Physical Activity and Weight Discussant: Glenn Gaesser As the prevalence of obesity has risen, so have weight loss at- tempts—without much apparent success. Epidemiological studies of women and men in the United States indicate a tendency for an inverse relationship between BMI and physical activity (Feskanich et al., 2002; Hu et al., 1999; Kushi et al., 1997). Studies in a number of other coun- tries show mixed findings, with most showing an inverse relationship between BMI and physical activity for men (Andersen et al., 2000; Hu et al., 2003; Rosengren and Wilhemsen, 1997; Thune et al., 1998) and women (Andersen et al., 2000; Hu et al., 2003; Mensink et al., 1999). However, some studies show no relationship for men (Bijnen et al., 1998; Smith et al., 2000) or for women (Thune et al., 1998). In studies reporting the strongest inverse associations between BMI and physical activity, the mean BMI is no more than one to two BMI units lower for
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68 PHYSICAL ACTIVITY WORKSHOP those at a high physical activity level than for those at a low physical activity level (Feskanich et al., 2002; Hu et al., 1999, 2003; Kushi et al., 1997). Data from Rosell et al. (2006) indicate that weight gain tended to be modestly less for more active than for less active persons over a 5-year period. Petrella et al. (2005) reported similar findings of a modest benefit of physical activity over a 10-year period among older persons. Notably, compared to weight change in younger persons, change in weight tends to be of smaller magnitude in older individuals. Larmarche et al. (1992) demonstrated that, among obese women who participated in exercise training, both those who lost fat and those who gained fat had improvements in VO2max, glucose tolerance, and blood lipid concentrations. Thus, regardless of the response measured by weight change or body fat change, individuals in the exercise program responded favorably in terms of indicators of health. Earlier work by Bjorntorp et al. (1970) found improvement in insulin sensitivity after exercise training with an increase in body fat. In summary, cohort studies reveal an inverse association between physical activity and BMI, but the effect is relatively small. Physical ac- tivity may be more effective in preventing unhealthy weight gain than in producing weight loss. Many weight-related health problems can be im- proved with exercise independently of weight loss. This latter point mer- its emphasis in view of the very modest effect of exercise on inducing weight change in women. Group Discussion Moderator: Peter Brubaker During the group discussion, workshop presenters and other partici- pants raised the following points: • Walking and running the same distance are not actually equiva- lent in energy expenditure. Several persons suggested that point- ing out the discrepancy would be counterproductive because the concept is difficult to understand. • Despite the modest effect of physical activity on weight loss, certain health benefits do not occur without a physical activity component of treatment.
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69 OBESITY AND WEIGHT MANAGEMENT • Maintenance of healthy weight when children are growing is a very important focus. Factors involved include physical educa- tion programs, allowed recess activities, extracurricular activi- ties, and potentially, short bouts of physical activity in the classroom. • Research in older disabled people has found that a moderate in- crease in VO2max leads to marked improvements in glucose me- tabolism, insulin levels, and glucose tolerance, implying benefit for older people in general. REFERENCES Andersen LB, Schnohr P, Schroll M, Hein MO. 2000. All-cause mortality asso- ciated with physical activity during leisure time, work, sports, and cycling to work. Arch Intern Med 160(11):1621–1628. Ballor DL, and Keesey RE. 1991. A meta-analysis of the factors affecting exer- cise-induced changes in body mass, fat mass, and fat-free mass in males and females. Int J Obes 15(11):717–726. Bijnen FCH, Casperson CJ, Feskins EJM, Saris WHM, Mosterd WL, Kromhout D. 1998. Physical activity and 10-year mortality from cardiovascular disease. Arch Intern Med 158(14):1499–1505. Bjorntorp P, De Jounge K, Sjostrom L, Sullivan L. 1970. The effect of physical training on insulin production in obesity. Metabolism 19(8):631–638. Borg P, Kukkonen-Harjula K, Fogelholm M, Pasanen M. 2002. Effects of walk- ing or resistance training on weight loss maintenance in obese, middle-aged men: A randomized trial. Int J Obesity 26(5):676–683. Bunyard LB, Katzel LI, Busby-Whitehead MJ, Wu Z, Goldberg AP. 1998. En- ergy requirements of middle-aged men are modifiable by physical activity. Am J Clin Nutr 68(5):1136–1142. Donnelly JE, Jacobsen DJ, Snyder Heelan KA, Seip R, Smith S. 2000. The ef- fects of 18 months of intermittent vs continuous exercise on aerobic capacity, body weight and composition, and metabolic fitness in previously sedentary, moderately obese females. Int J Obes 24(5):566–572. Donnelly JE, Hill JO, Jacobsen DJ, Potteiger J, Sullivan DK, Johnson SL, Heelan K, Hise M, Fennessey PV, Sonko B, Sharp T, Jakicic JM, Blair SN, Tran ZV, Mayo M, Gibson C, Washburn RA. 2003. Effects of a 16-month randomized controlled exercise trial on body weight and composition in young, overweight men and women: The Midwest Exercise Trial (MET). Arch Intern Med 163(11):1343–1350. Dunn AL, Marcus BH, Kampert JB, Garcia ME, Kohl HW, Brasel JA. 1999. Comparison of lifestyle and structured interventions to increase physical ac- tivity and cardiorespiratory fitness. J Am Med Assoc 281(4):327–334.
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70 PHYSICAL ACTIVITY WORKSHOP Feskanich D, Willett W, Colditz G. 2002. Walking and leisure-time activity and risk of hip fracture in postmenopausal women. J Am Med Assoc 288(18):2300–2306. Fogelholm M, Kukkonen-Harjula K, Nenonen A, Pasanen M. 2000. Effects of walking training on weight maintenance after a very-low-energy diet in premenopausal obese women: A randomized controlled trial. Arch Intern Med 160(14):2177–2184. Garrow J, Summerbell C. 1994. Meta analysis on the effect of exercise on the composition of weight loss. Int J Obes 18(7):516-517. Goldberg AP. 2006. Presentation at the Institute of Medicine Physical Activity Guidelines Development Workshop. Washington, DC. October 23. Hill JO, Wyatt HR, Reed GW, Peters JC. 2003. Obesity and the environment: Where do we go from here? Science 299(5608):853–855. Holcomb CA, Heim DL, Loughin TM. 2004. Physical activity minimizes the association of body fatness with abdominal obesity in white, premenopausal women: Results from the Third National Health and Nutrition Examination Survey. J Am Diet Assoc 104(12):1859–1862. Hu FB, Sigal RJ, Rich-Edwards JW, Colditz GA, Solomon CG, Willett WC, Speizer FE, Manson JE. 1999. Walking compared with vigorous physical ac- tivity and risk of type 2 diabetes in women: A prospective study. J Am Med Assoc 282(15):1433–1439. Hu G, Qiao Q, Silventoinen K, Eriksson JG, Jousilahti P, Lindstrom J, Valle TT, Nissinen A, Tuomilehto J. 2003. Occupational, commuting, and leisure-time physical activity in relation to risk for type 2 diabetes in middle-aged Finnish men and women. Diabetologia 46(3):322–329. Jakicic JM, Winters C, Lang W, Wing RR. 1999. Effects of intermittent exercise and use of home exercise equipment on adherence, weight loss, and fitness in overweight women. J Am Med Assoc 282(16):1554–1560. Jeffery RW, Wing RR, Sherwood NE, Tata DF. 2003. Physical activity and weight loss: Does prescribing higher physical activity goals improve out- come? Am J Clin Nutr 78(4):684–689. Klem ML, Wing RR, McGuire MT, Seagle HM, Hill JO. 1997. A descriptive study of individuals successful at long-term maintenance of substantial weight loss. Am J Clin Nutr 66(2):239–246. Kushi LH, Fee RM, Folsom AR, Mink PJ, Anderson KE, Sellers TA. 1997. Physical activity and mortality in postmenopausal women. J Am Med Assoc 277(16):1287–1292. Lamarche B, Despres JP, Pouliot MC, Moorjani S, Lupien PJ, Theriault G, Tremblay A, Nadeau A, Bouchard C. 1992. Is body fat loss a determinant fac- tor in the improvement of carbohydrate and lipid metabolism following aero- bic exercise training in obese women? Metabolism 41(11):1249–1256. LeCheminant JD, Jacobsen DJ, Hall MA, Donnelly JE. 2005. A comparison of meal replacements and medication in weight maintenance after weight loss. Am J Clin Nutr 24(5):347–353.
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71 OBESITY AND WEIGHT MANAGEMENT Leermakers EA, Perri MG, Shigaki CL, Fuller PR. 1999. Effects of exercise- focused versus weight-focused maintenance programs on the management of obesity. Addict Behav 24(2):219–227. Lynch NA, Nicklas BJ, Berman DM, Dennis KE, Goldberg AP. 2001. Reduc- tions in visceral fat during weight loss and walking are associated with im- provements in VO2max. J Appl Physiol 90(1):99–104. Mensink GBM, Ziese T, Kok FJ. 1999. Benefits of leisure-time physical activity on the cardiovascular risk profile at older age. Int J Epidemiol 28(4):659–666. Nicklas BJ, Rogus EM, Colman EG, Goldberg AP. 1996. Visceral adiposity, increased adipocyte lipolysis, and metabolic dysfunction in obese postmeno- pausal women. Am J Physiol 33(1):E72–E78. Ortmeyer HK, Ryan AS, Blumenthal JB, Joseph LJO, Goldberg AP. 2006. Ex- ercise and weight loss (WL), but not WL alone, affects skeletal muscle and adipose tissue lipoprotein lipase activity in post-menopausal women. Diabetes 55(Suppl 1):A5. Perri MG, McAllister DA, Gange JJ, Jordan RC, McAdoo G, and Nezu AM. 1988. Effects of four maintenance programs on the long-term management of obesity. J Consult Clin Psychol 56(4):529–534. Petrella RJ, Lattanzio CN, Demeray A, Varallo V, Blore R. 2005. Can adoption of regular exercise later in life prevent metabolic risk for cardiovascular dis- ease? Diabetes Care 28(3):694–701. Ravussin E, Swinburn BA. 1993. Metabolic predictors of obesity: Cross- sectional versus longitudinal data. Int J Obes 17(Suppl 3):S28–S31. Rosell M, Appleby P, Spencer E, Key T. 2006. Weight gain over 5 years in 21 966 meat-eating, fish-eating, vegetarian, and vegan men and women in EPIC- Oxford. Int J Obes 30(9):1389–1396. Rosengren A, Wilhelmsen L. 1997. Physical activity protects against coronary death and deaths from all causes in middle-aged men. Ann Epidemiol 7(1): 69–75. Ross R, Dagnone D, Jones PJ, Smith H, Paddags A, Hudson R, and Janssen I. 2000. Reduction in obesity and related comorbid conditions after diet-induced weight loss or exercise-induced weight loss in men. A randomized, controlled trial. Ann Intern Med 133(2):92–103. Ross R, Janssen I, Dawson J, Kungl AM, Kuk JL, Wong SL, Nguyen-Duy TB, Lee S, Kilpatrick K, and Hudson R. 2004. Exercise-induced reduction in obe- sity and insulin resistance in women: A randomized controlled trial. Obes Res 12(5):789–798. Slentz CA, Duscha BD, Johnson JL, Ketchum K, Aiken LB, Samsa GP, Houmard JA, Bales CW, and Kraus WE. 2004. Effects of the amount of exer- cise on body weight, body composition, and measures of central obesity: STRRIDE—a randomized controlled study. Arch Intern Med 164(1):31–39.
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72 PHYSICAL ACTIVITY WORKSHOP Smith GD, Shipley MJ, Batty GD, Morris JN, Marmot M. 2000. Physical activ- ity and cause-specific mortality in the Whitehall study. Public Health 114(5):308–315. Thune I, Njolstad I, Lochen M-L, Forde OH. 1998. Physical activity improves the metabolic risk profiles in men and women. The Tromso Study. Arch Intern Med 158(15):1633–1640.
Representative terms from entire chapter: