Although, much of the discussion around the health risks of obesity tends to focus around diabetes and heart disease, it is important not to forget that in women, excess weight is closely linked to the risk for post-menopausal breast cancer (by far the most common form of breast cancer).
Now, a team of researchers led by Kristin Campbell from the University of British Columbia, Vancouver, in a paper published in the Journal of Clinical Oncology, shows that weight loss achieved by calorie restriction and exercise can significantly reduce circulating levels of the sex-hormones implicated in the development of post-menopausal breast cancer.
The single-blind, 12-month, randomized controlled trial was conducted in 50 to 75 year-old women with a BMI greater than 25, who were assigned to one of three intervention groups: (1) reduced-calorie weight loss diet (“diet”; n = 118), (2) moderate- to vigorous-intensity aerobic exercise (“exercise”; n = 117), (3) combined reduced-calorie weight loss diet and moderate- to vigorous-intensity aerobic exercise (“diet + exercise”; n = 117), or (4) control (n = 87).
The weight loss diet intervention was a modification of the dietary component of the Diabetes Prevention Program36 and the Look AHEAD (Action for Health in Diabetes) lifestyle intervention programs, with a goal of daily energy intake of 1200 to 2000 kcal/d based on baseline weight, less than 30% daily energy intake from fat, and a 10% reduction in body weight by 6 months with maintenance to 12 months.
The exercise intervention goal was 45 minutes of moderate- to vigorous-intensity aerobic exercise, 5 days per week (225 minutes/wk). Each week, participants attended three monitored exercise sessions at the study facility and two at home. The program progressed to the maintenance target of 70% to 85% maximal heart rate for 45 minutes by week. Activities with four or more metabolic equivalents,38 such as brisk walking, were counted toward the prescribed exercise target.
These interventions resulted in significant weight loss at 12 months: diet alone and diet + exercise resulted in about 11-12 Kg weight loss, exercise alone resulted in about 3.5 Kg weight loss, the control group lost no weight.
Compared with controls, estrone decreased 9.6% with diet, 5.5% with exercise, and 11.1% with diet + exercise.
Estradiol decreased 16.2% with diet, 4.9% with exercise, and 20.3% with diet + exercise.
Sex hormone-binding globulin (SHBG) increased 22.4% with diet and 25.8% with diet + exercise.
Free estradiol decreased 21.4% with diet and 26.0% with diet + exercise.
Free testosterone decreased 10.0% with diet and 15.6% with diet + exercise.
Thus, weight loss significantly lowered serum estrogens and free testosterone, findings that support the notion that weight loss can likely reduce risk for breast caner by lowering the exposure to breast cancer biomarkers.
It may be worth recalling, that surgical weight loss studies have shown a remarkable 60% decrease in cancer mortality, including a reduction in breast cancers.
Thus, the potential of obesity treatment as a means to reducing breast cancer risk should not be underestimated.
AMS
Philadelphia, PA
Campbell KL, Foster-Schubert KE, Alfano CM, Wang CC, Wang CY, Duggan CR, Mason C, Imayama I, Kong A, Xiao L, Bain CE, Blackburn GL, Stanczyk FZ, & McTiernan A (2012). Reduced-Calorie Dietary Weight Loss, Exercise, and Sex Hormones in Postmenopausal Women: Randomized Controlled Trial. Journal of clinical oncology : official journal of the American Society of Clinical Oncology PMID: 22614972
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Calorie Restricted Diet Decreases Breast Cancer Biomarkers in Post-Menopausal Women,
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May 24th, 2012 at 6:51 pm
Was it the weight loss specifically that significantly lowered serum estrogens and free testosterone or was it the effects of dieting/exercising? Did the levels go back up once the diet and exercise regimes ended while weight remained stable?
June 1st, 2012 at 7:21 pm
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