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Developing policy and strategic initiatives to increase population levels of physical activity (PA) requires constant referral to the epidemiological evidence base. This paper updates the evidence that PA confers a positive benefit on health, using research studies in the peer-reviewed scientific literature published between 2000-2003. Areas covered include updates in all-cause mortality and in cardiovascular disease prevention, diabetes, stroke, mental health, falls and injuries, and in obesity prevention. Recent evidence on PA and all-cause mortality replicates previous findings, and is consistent with current Australian moderate PA recommendations. Recent papers have reinforced our understanding of the cardiovascular protective effects of moderate PA, with new evidence that walking reduces the risk of CVD and, in two studies, at least as much as vigorous activity. The evidence base for protective effects of activity for women, older adults and for special populations has strengthened. Cancer prevention studies have proliferated during this period but the best evidence remains for colon cancer, with better evidence accumulating for breast cancer prevention, and uncertain or mixed evidence for the primary prevention of other cancers. Important new controlled-trial evidence has accumulated in the area of type 2 diabetes: moderate PA combined with weight loss, and a balanced diet can confer a 50-60% reduction in risk of developing diabetes among those already at high risk. Limited new evidence has accumulated for the role of PA in promoting mental health and preventing falls.
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PMID:Updating the evidence that physical activity is good for health: an epidemiological review 2000-2003. 1521 97

Nutritional challenges are particularly relevant to women. Almost 62% of women are overweight; of these women, 33% are obese. The incidence of obesity is even greater in non-Hispanic Black and Mexican American women. Women who are overweight or obese experience a greater number of adverse health outcomes, including an increased incidence of cardiovascular disease and breast and colon cancer. Dietary patterns influence health outcomes, with a heart-healthy pattern having the most positive health outcomes. Health care providers should encourage women to consume a diet high in fruits and vegetables and low in total and saturated fats.
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PMID:Obesity and nutrition in women throughout adulthood. 1556 71

Many peptides, hormones and growth factors have been implicated in the control of cell renewal in the gastrointestinal epithelium. Leptin is present in the stomach and salivary glands and leptin receptors are seen throughout the gut. Leptin can stimulate mitogen-activated protein kinase activity in vitro and short-term infusion has been reported to have a proliferative action on the colon in vivo, suggesting a biological link between obesity, physical activity and colon cancer. Food intake is one of the most important determinants of intestinal mucosal cell renewal, thus any direct effects of leptin on the gut may be hidden. This problem has been avoided experimentally by maintaining animals on total parenteral nutrition (TPN). Male Wistar rats were anaesthetized and cannulae were inserted into the jugular vein to deliver the TPN diet to which had been added 0, 0.5, 2.5, or 10 mg/kg of recombinant murine leptin. Orally fed rats were also studied. After 6 days of treatment, all animals were injected with vincristine and killed 2 h later. Tissue weight was recorded and crypt cell proliferation (arrested metaphases) and crypt fission were scored in 'microdissected' crypts. Leptin infusion led to a small decrease in body weight and in the weight of the caecum. Intestinal cell proliferation was significantly reduced by TPN when compared to the orally fed rats, but the addition of leptin had no effect on the small intestine or colon. Crypt fission was also significantly lowered in the TPN group. Fission was slightly but significantly increased in the proximal and mid-colon of the leptin-treated rats, but was decreased in the distal colon. Although leptin did not significantly alter cell proliferation, it had significant effects on the process of crypt fission in the colon, which varied according to the exact locality.
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PMID:Leptin, cell proliferation and crypt fission in the gastrointestinal tract of intravenously fed rats. 1567 64

Energy balance, or the ability to maintain body weight by balancing energy intake with energy expenditure, appears to be important in the etiology of colon cancer. One possible mechanism whereby energy balance may be associated with colorectal cancer is through its association with insulin. In our study, we evaluate the interaction between polymorphisms in 4 genes thought to be involved in insulin-related functions and components of energy balance with risk of colorectal cancer. Data from 2 population-based case-control studies of colon and rectal cancer conducted in Utah and Northern California were used to evaluate associations between body mass index (BMI), physical activity, energy intake and sucrose-to-fiber ratio and a CA repeat polymorphism of the IGF1 gene, the A/C polymorphism at nucleotide -202 of the IGFBP3, the G972R polymorphism of the IRS1 gene and the G1057D polymorphism of the IRS2 gene. A total of 1,346 incident colon cancer cases and 1,544 population-based controls and 952 incident rectal cancer cases and 1,205 controls were available for analysis. Inconsistent associations were identified between BMI, physical activity, energy intake and insulin-related genes. The 192/192 IGF1 genotype was associated with significant reduction in colon cancer risk among those with high physical activity (odds ratio [OR] 0.57; 95% confidence interval [CI] 0.39-0.83; p interaction 0.01). Although there was no significant pattern of interaction between either BMI or energy intake and polymorphisms assessed, specific sources of energy did appear to be more related to colon cancer risk in the presence of specific IRS2 and IGF1 genotypes. A high sucrose-to-fiber ratio increased risk of colon cancer in men who had the IRS2 DD genotype and among men who did not have the 192/192 IGF1 genotype. In summary, these data support the importance of components of energy balance in risk of colorectal cancer. Obesity, physical activity and energy intake appear to alter risk of colorectal cancer; however, the risk appears to be minimally influenced by genetic variants evaluated.
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PMID:Energy balance, insulin-related genes and risk of colon and rectal cancer. 1568 7

Hyperinsulinemia, hyperglycemia, and elevated insulin-like growth factor (IGF)-1 levels have been implicated in the etiology of colorectal cancer. However, the joint effects of insulin and IGF-I have not been considered, and whether hyperinsulinemia or hyperglycemia is more etiologically relevant is unclear. IGF binding protein-1 (IGFBP-1) has been hypothesized to mediate the effects of insulin, but epidemiologic data on IGFBP-1 are sparse. We conducted a nested case-control study among the 32,826 women of the Nurses' Health Study who provided a blood sample in 1989 to 1990. After excluding diabetics, we confirmed 182 incident colorectal cancer cases over 10 years of follow-up and 350 controls. Cases were matched to two controls on year of birth, date of blood draw, and fasting status. C-peptide levels were weakly associated with risk of colon cancer [top quartile (Q4) versus bottom quartile (Q1): multivariable relative risk (MVRR), 1.76; 95% confidence interval (95% CI), 0.85-3.63]. Fasting IGFBP-1 was inversely associated with risk of colon cancer (MVRR, 0.28; 95% CI, 0.11-0.75). We observed no clear association between glycosylated hemoglobin and risk for colorectal cancer. The IGF-I to IGFBP-3 molar ratio was associated with colon cancer risk (MVRR, 2.82; 95% CI, 1.35-5.88), and women with low levels of both IGF-I/IGFBP-3 and C-peptide (or high IGFBP-1) were at low risk, and elevation of either was sufficient to increase risk. Although altering IGF-I levels may not be practical, the growing burden of obesity and consequently hyperinsulinemia, which seems increasingly important for colon cancer, may be a target for effective prevention.
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PMID:A prospective study of C-peptide, insulin-like growth factor-I, insulin-like growth factor binding protein-1, and the risk of colorectal cancer in women. 1582 55

Peroxisome proliferator-activated receptor-gamma (PPARgamma) has been hypothesized as being involved in colorectal cancer given its role in adipocyte development and insulin resistance. In this study we evaluated the association between the Pro12Ala (P12A) PPARgamma polymorphism and body mass index (BMI), waist-to-hip ratio (WHR), physical activity level, and energy intake and risk of colorectal cancer using data from a population-based, case-control study of colon cancer (1,577 cases and 1,971 controls) and rectal cancer (794 cases and 1,001 controls). We further evaluated how the P12A PPARgamma polymorphism is associated with obesity and fat pattern in the control population. The odd ratio for PPARgamma PA or AA genotype relative to the PP genotype for colon cancer was 0.9 (95% confidence interval, CI=0.8-1.0) and for rectal cancer was 1.2 (95% CI=1.0-1.5) adjusting for race, age, and sex. P12A PPARgamma did not significantly interact with BMI, WHR, energy intake, and energy expenditure to alter risk of colon or rectal cancer. Furthermore, the P12A PPARgamma polymorphism was not associated with obesity or WHR in the control population; it did not interact with energy intake or energy expenditure to alter risk of obesity or large WHR. These data do not support the hypothesis that the P12A PPARgamma polymorphism is associated with colon or rectal cancer through regulation of energy balance.
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PMID:PPARgamma, energy balance, and associations with colon and rectal cancer. 1586 Apr 37

Excess weight has been associated with increased risk of cancer. The effect of body mass index (BMI, kg/m(2)) on overall cancer risk and on risk of developing several common cancer types was examined in a population-based cohort study. Height and weight measurements were available for 35,362 women and 33,424 men recruited in the Northern Sweden Health and Disease Cohort between 1985 and 2003. Among cohort members, 2,691 incident cancer cases were identified. The association of BMI with cancer risk was examined using Poisson regression. Women with BMI > 27.1 (top quartile) had a 29% higher risk of developing any malignancy compared to women with BMI of 18.5-22.2 (lowest quartile), which increased to 47% in analysis limited to nonsmokers. Analyses according to WHO cut-off points showed that obese women (BMI > or = 30) had a 36% higher risk of cancer than women with BMI in the normal range (18.5-25). Individual cancer sites most strongly related to obesity were endometrium (risk for top quartile = 3.53, 95% confidence interval 1.86-7.43), ovary (2.09, 1.13-4.13) and colon (2.05, 1.04-4.41). BMI was inversely related to breast cancer occurring before age 49 (0.58, 0.29-1.11, p(trend) < 0.04). In men, there was no association of BMI with overall cancer risk. Obese men (BMI > or = 30), however, were at increased risk of developing kidney cancer (3.63, 1.23-10.7) and, after exclusion of cases diagnosed within 1 year of recruitment, colon cancer (1.77, 1.04-2.95). Our study provides further evidence that BMI is positively associated with cancer risk. In women from northern Sweden, up to 7% of all cancers were attributable to overweight and obesity and could be avoided by keeping BMI within the recommended range.
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PMID:Body mass index and cancer: results from the Northern Sweden Health and Disease Cohort. 1604 63

Overweight and obesity increase the risk of developing several cancers. Once cancer develops, individuals may be at increased risk of recurrence and poorer survival if they are overweight or obese. A statistically significant association between overweight or obesity and breast cancer recurrence or survival has been observed in the majority of population-based case series; however, adiposity has been shown to have less of an effect on prognosis in the clinical trial setting. Weight gain after breast cancer diagnosis may also be associated with decreased prognosis. New evidence suggests that overweight/obesity vs normal weight may increase the risk of poor prognosis among resected colon cancer patients and the risk of chemical recurrence inprostate cancer patients. Furthermore, obese cancer patients are at increased risk for developing problems following surgery, including wound complication, lymphedema, second cancers, and the chronic diseases affecting obese individuals without cancer such as cardiovascular disease and diabetes. Mechanisms proposed to explain the association between obesity and reduced prognosis include adipose tissue-induced increased concentrations of estrogens and testosterone, insulin, bioavailable insulin-like growth factors, leptin, and cytokines. Additional proposed mechanisms include reduced immune functioning, chemotherapy dosing, and differences in diet and physical activity in obese and nonobese patients. There have been no randomized clinical trials testing the effect of weight loss on recurrence or survival in overweight or obese cancer patients, however. In the absence of clinical trial data, normal weight, overweight, and obese patients should be advised to avoid weight gain through the cancer treatment process. In addition, weight loss is probably safe, and perhaps helpful, for overweight and obese cancer survivors who are otherwise healthy.
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PMID:Obesity and cancer: the risks, science, and potential management strategies. 1605 36

Among men there is epidemiological evidence for an association between obesity and increased risk of renal cell carcinoma, colon cancer and adenocarcinoma of the oesophagus. The evidence for other cancer sites remains inconsistent. We conducted a large population-based, multi-site, case-control study of environmental causes of cancer among males in Montreal, Canada. Among the many questionnaire items collected by interview were height and usual weight. We compared height, weight and body mass index (BMI) among individuals with 11 different cancer types (combined N=3016) and population-based controls (N=509). Linear regression was used to model the relationship of the disease status with each of three dependent continuous variables (height, weight and BMI), while adjusting for covariates. For most cancer groups, weight and BMI were lower than among population controls. Because of potential information bias and reverse causality bias, we focused on the comparisons among cancer types. The lowest BMI values were observed among men with squamous cell carcinoma of the oesophagus, lung and stomach cancers. The highest BMIs were reported by men with prostate and kidney cancers, and oesophageal adenocarcinoma. Inconsistencies in the epidemiological literature on obesity and cancer risk could be related to the difficulties in obtaining unbiased reports of pre-disease weight and to publication bias.
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PMID:Comparison of self-reported height and weight by cancer type among men from Montreal, Canada. 1617 48

Regular physical activity improves quality of life and reduces risk for coronary heart disease, colon cancer, hypertension, diabetes, and overall mortality. Physical activity also has been associated with reduced symptoms of depression and greater independence. A sedentary lifestyle is associated with obesity. However, despite the health benefits of physical activity, 23.1% of adults in the United States report they do not engage in any leisure-time physical activity. Neighborhood environment (e.g., sidewalks and street lighting), perceived trustworthiness of neighbors, and perceptions of neighborhood safety all have been associated with levels of physical activity. During 2004, to assess the association between these factors and leisure-time physical inactivity in eastern Travis County, Texas, the local health department collected and analyzed data by using the methodology of the Behavioral Risk Factor Surveillance System (BRFSS). This report describes the results of that analysis, which indicated that persons who perceived their neighborhoods as less than extremely safe were more than twice as likely to have no leisure-time physical activity, and those who perceived their neighborhoods as not at all safe were nearly three times as likely to have no leisure-time physical activity. Public health agencies promoting physical activity in neighborhoods should consider how residents perceive their safety and design programs that specifically address those safety concerns.
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PMID:Perceptions of neighborhood characteristics and leisure-time physical inactivity--Austin/Travis County, Texas, 2004. 1617 84


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