Weight management

Using UK Biobank data, researchers constructed a cancer prevention adherence score incorporating healthy body weight among WCRF/AICR recommendations. Cox proportional hazards models showed that in women without recent dietary changes, higher lifestyle adherence was inversely associated with breast cancer in situ risk (HR = 0.92 per unit increase, 95% CI = 0.85–0.99). The overall cohort demonstrated a non-significant trend (HR = 0.96, 95% CI = 0.91–1.03). Among women who changed their diet due to illness, no association was found (HR = 1.04, 95% CI = 0.94–1.15).

View Source →

In this population-based cohort of 13,802 women followed prospectively, pre-diagnostic metabolic factors (BMI, waist:hip ratio, serum lipids, blood pressure) were measured. Of 557 women who developed invasive breast cancer, those from south Asia with an unfavorable metabolic profile had 2.3 times higher breast cancer risk compared to western European women (HR 2.30, 95% CI 1.18–4.49). Among women with triple-negative breast cancer, above-median triglycerides:HDL-cholesterol ratio (>0.73) was associated with 2.9 times higher overall mortality (HR 2.88, 95% CI 1.02–8.11) over a median 7.7-year follow-up. These findings support metabolic health optimization as part of breast cancer prevention, particularly for women migrating from low- to high-incidence countries.

View Source →

Pooled data from 121,435 women with invasive breast cancer across 67 studies (16,890 deaths over 10 years) showed that BMI ≥30 versus 18.5-25 kg/m² was associated with a hazard ratio of 1.19 (95% CI 1.06-1.34) for 10-year all-cause mortality. The association was consistent across tumor subtypes with no evidence of heterogeneity by ER status or intrinsic-like subtype (P adj > 0.30). Cox regression models adjusted for relevant covariates confirmed obesity as an independent modifiable prognostic factor.

View Source →

In a prospective cohort of 150,257 women (median age 51 at entry) followed for an average of 14 years (SD = 3.9), 6,532 breast cancer cases occurred. Compared with women maintaining stable weight (±2.5 kg), those gaining >10 kg from age 20 had significantly elevated postmenopausal breast cancer risk: HR = 1.42 (95% CI: 1.22–1.65) among women lean at age 20, HR = 1.23 (95% CI: 1.04–1.44) in ever HRT users, HR = 1.40 (95% CI: 1.16–1.68) in never HRT users, and HR = 1.46 (95% CI: 1.15–1.85) for ER+PR+ breast cancer specifically.

View Source →

Among 96,869 women in the NOWAC cohort, the Healthy Lifestyle Index incorporating BMI as one of five components showed a statistically significant inverse association with postmenopausal breast cancer (HR 0.97 per one-point increment, 95% CI: 0.96–0.98). Cox proportional hazard regression with multiple imputation for missing data confirmed the association. Higher HLI scores, reflecting healthier BMI among other factors, corresponded to lower cancer incidence.

View Source →

In the EPIC cohort of 150,257 women (median age 51 at entry) followed for an average of 14 years (SD 3.9), 6,532 breast cancer cases were identified. Women who gained >10 kg from age 20 compared to those with stable weight (±2.5 kg) had significantly elevated postmenopausal breast cancer risk: HR 1.42 (95% CI 1.22–1.65) among women lean at age 20, HR 1.23 (95% CI 1.04–1.44) in ever HRT users, HR 1.40 (95% CI 1.16–1.68) in never HRT users, and HR 1.46 (95% CI 1.15–1.85) for estrogen-and-progesterone-receptor-positive breast cancer. The association was consistent regardless of HRT use history.

View Source →

In this case-control study from the Mohammed VI Centre in Casablanca, anthropometric analysis showed the odds of developing breast cancer were 1.78 (OR) in overweight women and 2.39 in obese women compared to normal-weight women. Women with a waist circumference greater than 88 cm had an OR of 1.82, and those with a waist-to-hip ratio above 0.85 had an OR of 1.70. At age 10, having a large body figure carried an OR of 1.60 compared to a small figure. The study concluded that overweight status is a major modifiable risk factor for breast cancer in this population.

View Source →

This systematic review examined body mass and physical activity interactions across multiple epidemiological studies and found obesity had a positive association with breast cancer incidence in women. Evaluation of the 'fat but fit' hypothesis using formal interaction terms between body fatness and physical activity revealed no evidence that high physical activity or fitness attenuates the obesity-related breast cancer risk. The review concluded that obesity-related cancer risks are not eliminated by high fitness levels, supporting the independent necessity of weight management alongside physical activity to reduce breast cancer incidence in women.

View Source →

Meta-analysis of 7 prospective European cohorts (24,751 women; mean age 63 years; median follow-up 12 years). Significant effect modification by hormone therapy (HT) use was observed for postmenopausal breast cancer (P interaction < 0.001). Never-HT users showed approximately 20% increased breast cancer risk per standard deviation increment of BMI, waist circumference, and hip circumference, compared to substantially lower risk elevations among ever-HT users. Overall obesity-related cancer hazard ratios per SD were 1.11 (95% CI 1.02-1.21) for BMI and 1.13 (95% CI 1.04-1.23) for waist circumference.

View Source →

The IARC working group found sufficient evidence that absence of excess body fatness lowers postmenopausal breast cancer risk. Numerous studies demonstrated a positive association, with a relative risk of approximately 1.1 (95% CI, 1.1–1.2) per 5 BMI units, particularly for estrogen-receptor-positive tumors. Waist circumference and body-weight gain in adulthood were also positively associated with postmenopausal breast cancer risk. Among women who received hormone-replacement therapy, no association was observed with postmenopausal breast cancer. Notably, for premenopausal breast cancer, consistent inverse associations between BMI and risk were observed. A large volume of evidence supported an association between increased BMI near the time of cancer diagnosis and reduced survival in breast cancer patients.

View Source →

Among women in a representative Scottish cohort of 3839 children followed for 67 years to age 77, each 1 standard deviation increase in BMI at age 11 was associated with a 27% higher rate of breast cancer mortality (hazard ratio 1.27; 95% confidence interval: 1.04 to 1.56). This was the strongest single-cause association observed in the study, exceeding the hazard ratios for all-cause mortality (HR 1.09; 95% CI: 1.03–1.14) and all cancers combined (HR 1.12; 95% CI: 1.03–1.21). Results were adjusted for childhood socioeconomic status and cognitive ability.

View Source →

The EPIC cohort followed 242,918 postmenopausal women for a median of 10.9 years, identifying 7,756 incident breast cancer cases. Anthropometry was one of five HLIS components scored 0-4. Comparing the highest to the second HLIS category yielded an adjusted HR of 0.74 (95% CI: 0.66-0.83) for overall breast cancer. A 3% risk reduction was observed per point increase in the HLIS. The protective effect was evident for hormone receptor double positive breast cancer (adjusted HR = 0.81, 95% CI: 0.67-0.98) and hormone receptor double negative breast cancer (adjusted HR = 0.60, 95% CI: 0.40-0.90).

View Source →

A case-control study of 59 breast cancer cases and 59 matched neighborhood controls at Kudus Hospital (2010) identified obesity as a statistically significant risk factor for breast cancer (p=0.00; OR=4.49; 95% CI=2.01–10.02). Obese women had approximately 4.5 times higher odds of developing breast cancer compared to non-obese women. Chi-square analysis confirmed the association at α=0.05 significance level.

View Source →

In a pooled analysis of 5,683 operable breast cancer patients from four randomized clinical trials (GEICAM/9906, GEICAM/9805, GEICAM/2003-02, BCIRG 001), severely obese patients (BMI ≥ 35) had a 26% increased risk of recurrence (HR = 1.26, 95% CI 1.00-1.59, P = 0.048), 32% increased breast cancer mortality (HR = 1.32, 95% CI 1.00-1.74, P = 0.050), and 35% increased overall mortality (HR = 1.35, 95% CI 1.06-1.71, P = 0.016) compared to patients with BMI < 25. Obese patients with BMI 30.0-34.9 did not show significantly worse outcomes. The harmful prognostic effect of severe obesity was consistent across all pathological subtypes in multivariate analyses adjusting for age, tumor size, nodal status, and other clinical factors.

View Source →

In 168 Mexican women (84 cases, 84 controls), obesity was significantly associated with breast cancer risk. Bivariate analysis showed OR 3.09 (95% CI 1.64–5.80) for obesity, OR 3.10 (95% CI 1.65–5.84) for elevated BMI, and OR 3.43 (95% CI 1.81–6.47) for elevated waist-hip ratio. Multivariate analysis using a BMI cutoff of 34 yielded OR 32.96 (p<0.002), indicating a 32-fold increased risk of breast cancer at BMI ≥34.

View Source →

The European Cancer Prevention Organization working group consensus declared that obesity is to be avoided and that it should be a public health priority in cancer prevention. Body mass index was identified as a poor parameter for body fat content, with the recommendation that body impedance measures of fat and lean body mass replace BMI in future epidemiological studies. Breast cancer is 1 of 7 cancer types potentially related to fat consumption and energy balance. The Danish population obtains 43% of energy from fat with a steadily increasing 30-year trend. The combined effect of known dietary and environmental exposures was calculated, and even the most conservative estimation of explainable cancer cases was very low compared to actually observed cases.

View Source →

In a population-based cohort of 5,394 women diagnosed with AJCC Stage I–III locoregional breast cancer in 2004, drawn from National Program of Cancer Registries in seven U.S. states, BMI was examined in relation to mortality using Cox proportional hazards regression adjusted for demographic and clinical covariates. Among women with Stage I disease, those with BMI ≥35 kg/m² had significantly higher breast cancer-specific mortality compared to normal-weight women (BMI 18.5–24.9 kg/m²), with a hazard ratio of 4.74 (95% CI 1.78–12.59). This association was not observed in women with more advanced Stage II or III disease. For overall mortality among women aged 70 or older, each 5 kg/m² increase in BMI was associated with lower all-cause mortality (HR 0.85, 95% CI 0.75–0.95), while no significant association was found for women under 70.

View Source →