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Study Suggests That Body Composition Is Key Player in Controlling Cancer Risks
 
 
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Scientists have long thought that limiting the calories a person consumes can prevent, or at least slow the progression of certain cancers. But research at UAB using mice suggests that body composition - whether a person is lean or obese - actually is key to reducing cancer risks.
 
Newswise.com - Scientists have long thought that limiting the calories a person consumes can prevent, or at least slow the progression of certain cancers. But research at UAB (University of Alabama at Birmingham) using mice suggests that body composition - whether a person is lean or obese - actually is key to reducing cancer risks.
 
In other words, how the body handles calories is much more important to controlling cancer risks than how many or how few calories are consumed-a finding that could have strong implications for preventing and treating cancer in humans.
 
In findings published in the Jan. 1 issue of Cancer Research, the UAB team found that transgenic mice predisposed to prostate cancer that were lean had a much slower progression of cancer than did heavier mice.
 
"This study suggests that body composition, being lean as opposed to being obese, has a greater protective effect against cancer," said Tim R. Nagy, Ph.D., UAB professor of nutrition sciences and study principal investigator. "Excess calorie retention, rather than consumption, confers cancer risk."
 
Nagy's team placed transgenic mice into two controlled environments, either 27 degrees centigrade or 22 degrees centigrade, and fed them equal amounts of food. The mice living at the cooler environment needed more energy to regulate their internal temperature and so burned more calories simply to stay warm. These mice lost weight and were leaner than the mice kept at the warmer temperature.
 
The mice kept at 27 degrees were heavier and had more fat mass. Cancer in these mice progressed at a much greater rate than in the lean mice. The heavier mice also had higher levels of leptin, a hormone associated with obesity that promotes cancer, and lower levels of adiponectin, a hormone that appears to protect against cancer.
 
"We believe this is the first study to show that the beneficial effect on cancer risk by reducing the number of calories in the diet is more closely related to leanness or obesity than previously thought, and not a factor of food intake or total calories ingested," Nagy said.
 
Nagy's team kept two other groups of transgenic mice in the 27 and 22 degree environments. These mice were allowed to eat as much food as they wished. The mice in the cooler environment ate 30 percent more food than the mice in the warmer environment, indicating they required the additional calories to maintain body temperature.
 
The body composition for both of these groups of mice remained the same; and both had the same level of cancer progression, indicating that the increased calorie intake from the cooler-temperature mice plays no role in cancer protection.
 
This research was supported by funding from the National Cancer Institute, part of the National Institutes of Health.
 
ABSTRACT
 
Cancer Progression in the Transgenic Adenocarcinoma of Mouse Prostate Mouse Is Related to Energy Balance, Body Mass, and Body Composition, but not Food Intake

 
Derek M. Huffman 1, Maria S. Johnson , Amanda Watts , Ada Elgavish , Isam A. Eltoum , Tim R. Nagy * 1 Departments of 1Nutrition Sciences, 2Genetics, and 3Pathology, University of Alabama at Birmingham, Birmingham, Alabama
 
Calorie restriction can inhibit or delay carcinogenesis, reportedly due to a reduction in calorie intake rather than by concurrent changes in body mass and/or composition. Our objective was to test the hypothesis that body mass and/or composition have an important effect, independent of energy intake, on the benefits or hazards associated with calorie restriction or overeating, respectively. In the first experiment, transgenic mice that spontaneously develop prostate cancer [transgenic adenocarcinoma of mouse prostate (TRAMP)] were housed at 27 C or 22 C and pair fed the same diet for 21 weeks (95% of ad libitum intake at 27 C). In the second experiment, TRAMP mice were housed at 27 C or 22 C and fed the same diet ad libitum for 21 weeks. Despite a similar calorie intake, pair-fed mice at 27 C (PF27) were heavier (28.3 ± 3.3 versus 17.6 ± 1.6 g at 21 weeks; P < 0.001; mean ± SD) and had greater fat (6.4 ± 2.1 versus 1.9 ± 0.3 g; P < 0.001) and lean mass (P < 0.001) than pair-fed mice at 22 C. Furthermore, PF27 mice had greater levels of serum leptin (P < 0.001), lower levels of adiponectin (P < 0.05), and a greater frequency of prostatic adenocarcinoma (P < 0.05). In contrast, ad libitum-fed mice housed at 22 C consumed 30% more calories than ad libitum-fed mice at 27 C, but there was no difference between groups in body composition or cancer progression. These results imply that the ability of calorie restriction to inhibit or delay cancer incidence and progression is mediated in part by changes in energy balance, body mass, and/or body composition rather than calorie intake per se, suggesting that excess calorie retention, rather than consumption, confers cancer risk. [Cancer Res 2007;67(1):417-24]
 
 
 
 
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