Hormonal
Weight loss significantly reduces the risk of postmenopausal breast cancer, with a dose-response relationship where greater weight loss leads to greater decreases in estrogen and increased sex hormone-binding globulin (SHBG).
If you are postmenopausal and overweight, losing even a small amount of weight (more than 5% of your body weight) can significantly lower your risk of breast cancer. This happens because losing fat reduces the amount of estrogen your body produces and increases the protein that binds up remaining estrogen, protecting your breast tissue. You don't need to reach an 'ideal' weight to see benefits; the act of losing weight itself changes your hormonal environment in a protective way.
A meta-analysis assessing the effect of weight loss on breast cancer incidence found that weight loss significantly reduces breast cancer risk in both pre- and post- menopausal women (112). ... women who lost weight (> 5% of body weight) compared to women with stable weight had a significantly lower breast cancer risk (HR, 0.88, 95% CI, 0.78–0.98). ... greater weight loss was associated with greater decreases in estrone, estradiol, free estradiol, and free testosterone, as well as a greater increase in SHBG (120).
Why this rating
Supported by multiple observational studies (Women's Health Initiative, Nurses' Health Study), a meta-analysis, and mechanistic trials, though the paper notes more rigorous clinical trials are needed.
Source
The Many Faces of Obesity and Its Influence on Breast Cancer Risk
Tanya Agurs‐Collins et al. · Frontiers in Oncology · 2019
DOI 10.3389/fonc.2019.00765
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- Obesity increases the risk of estrogen-receptor-positive (ER+) breast cancer in postmenopausal women through the 'obesity-inflammation-aromatase axis,' where visceral fat produces estrogen via the enzyme aromatase.Strong
- Obesity increases the risk of triple-negative breast cancer (TNBC) in premenopausal women, primarily through abdominal (visceral) obesity rather than overall BMI.Good
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