Intentional weight loss and incidence of obesity-related cancers: the Iowa Women's Health Study

Abstract

OBJECTIVE:To examine the association of voluntary vs involuntary weight loss with incidence of cancer in older women. DESIGN: Prospective cohort study from 1993 to 2000, with cancer incidence identified through record linkage to a cancer registry. SUBJECTS: A total of 21 707 postmenopausal women initially free of cancer. MESUREMENTS: Women completed a questionnaire about intentional and unintentional weight loss episodes of Z20 pounds during adulthood. RESULTS: Compared with women who never had any Z20 pounds weight loss episode, women who ever experienced intentional weight loss Z20 pounds but no unintentional weight loss had incidence rates lower by 11% for any cancer (RR ¼ 0.89, 95% CI 0.79-1.00), by 19% for breast cancer (RR ¼ 0.81, 95% CI 0.66-1.00), by 9% for colon cancer (RR ¼ 0.91, 95% CI 0.66-1.24), by 4% for endometrial cancer (RR ¼ 0.96, 95% CI 0.61-1.52), and by 14% for all obesity-related cancer (RR ¼ 0.86, 95% CI 0.74-1.01) after adjusting for age, body mass index, waist-to-hip ratio, physical activity, education, marital status, smoking status, pack-years of cigarettes, current estrogen use, alcohol use, parity, and multivitamin use. Furthermore, although overweight women were at increased risk of several cancers, women who experienced intentional weight loss episodes of 20 or more pounds and were not currently overweight were observed to have an incidence of cancer similar to nonoverweight women who never lost weight. Unintentional weight loss episodes were not associated with decreased cancer risk. CONCLUSIONS: These findings suggest that intentional weight loss might reduce risk of obesity-related cancers.

Metabolic surgery and cancer

“…29 The role, therefore, for intentional weight loss to decrease cancer rates has gained increased favor, although this has proven difficult to achieve with diet and lifestyle therapies. 30 Both randomized and prospective studies reveal that the long-term weight loss with intensive lifestyle intervention in diabetic patients with a body mass index of 30 kg/m 2 is approximately 2% at 2 years 31 and 10 years 32 and is even less in patients 7 with a body mass index above 35 kg/m 2 . The significant weight reductions required for the proposed decrease in cancer risk, however, can be consistently achieved in the vast majority of patients who undergo metabolic surgery (Table 1).…”

Body Mass Index and Cancer Risk: The Evidence for Causal Association~!2009-04-22~!2009-06-16~!2010-07-13~!

“…However, in humans, there are no randomized data on this issue; data in the main comes from secondary analyses of large observational cohort studies. Most studies have been pertinent to risk reduction of breast cancer [35][36][37][38][39][40][41], with smaller numbers of studies on risk reduction of endometrial [42] and prostate cancers [43]. The emphasis on studies in breast cancer, however, serves to demonstrate that the question of reversibility is not trivial.…”

Body Mass Index and Cancer Risk: The Evidence for Causal Association

“…However, in humans, there are no randomized data on this issue; data in the main comes from secondary analyses of large observational cohort studies. Most studies have been pertinent to risk reduction of breast cancer [35][36][37][38][39][40][41], with smaller numbers of studies on risk reduction of endometrial [42] and prostate cancers [43]. The emphasis on studies in breast cancer, however, serves to demonstrate that the question of reversibility is not trivial.…”

“…Third, within these cohorts, there are three broad questions: (i) is weight loss in later reproductive years associated with reduced risk of post-menopausal breast cancer risk; (ii) is weight loss in early adult years associated with reduced risk of post-menopausal breast cancer; and (iii) is weight loss in early adult years associated with reduced risk of pre-menopausal breast cancer risk -and not all three are addressed in all papers. Accepting these limitations and difference in study design, the following observations can be stated for breast cancer: (i) weight loss in later reproductive years is associated with reduced risk of post-menopausal breast cancer risk in some [36,40] but not all studies [37][38][39]41]; (ii) weight loss in early reproductive years appears to reduce risk of post-menopausal breast cancer in most studies [35,37,38,41]; and (iii) whether or not weight loss in early reproductive years is associated with reduced risk of premenopausal breast cancer risk is equivocal as the data are sparse [39].…”