An estimated 1.38 million new cases of breast cancer (BC) are diagnosed each year in women worldwide. Of these, the majority are categorized as invasive ductal cell carcinoma. Subgroups of BC are frequently distinguished into five “intrinsic” subtypes, namely, luminal A, luminal B, normal-like, HER2-positive, and basal-like subtypes. Epidemiological evidence has shown that anthropometric factors are implicated in BC development. Overall consistent positive associations have been observed between high body mass index (BMI) and waist-to-hip ratio (WHR) and the risk of BC among postmenopausal women, while conflicting results persist for premenopausal BC, both for BMI and for other anthropometric parameters as well as across ethnic groups. Furthermore, some evidence suggests that body size, body shape, and weight gain during childhood or adolescence may play a role in the risk of BC. In this paper, we describe the evidence linking anthropometric indices at different ages and BC risk, in order to improve our understanding of the role of body fat distribution in the risk of BC, investigate differences in these associations according to menopausal status and ethnic groups, and discuss the potential biological mechanisms linking body size and BC risk.
Breast cancer (BC) is the most frequently diagnosed cancer in women worldwide, accounting for 23% (1.38 million) of the total new cancer cases in 2008 [
The incidence rates of BC show a heterogeneous distribution, while Western countries present the highest incidence rates, the lowest incidences are observed in low resource countries. BC ranks as the fifth cause of death from cancer overall (458,000 deaths), but is still the most frequent cause of cancer death in women in both developing (269,000 deaths) and developed regions (189,500 deaths) [
The risk factors related to reproductive factors such as delayed childbearing, lower parity, and reduced breastfeeding are becoming more prevalent in countries in economic transition but do not fully explain the increase of BC incidence rates. Other risk factors such as changes in lifestyle, physical activity, and anthropometry as well as ethnicity and genetic susceptibility play a role in the development of BC [
Overweight and obesity have become major public health challenges throughout the world in both high and low income countries, with over 1 billion overweight and 315 million obese adults currently estimated worldwide [
Anthropometric indices, height, weight, body mass index (BMI), waist circumference (WC), hip circumference (HC), or waist-to-hip ratio (WHR), are commonly used as tools for assessing overweight/obesity and recently methods for evaluating body shape and body size at different ages have also been used. Several studies and meta-analyses have examined the associations between anthropometric indices and BC among both pre- and postmenopausal women. Overall consistent positive associations have been observed between BMI and WHR and the risk of BC among postmenopausal women [
To review the epidemiologic literature on the association of overweight, obesity, fat distribution, and BC risk, we conducted a MEDLINE and PUBMED search including all publications using height, weight, BMI, WC, HC, WHR, anthropometric factors, body shape, early life body size, BC, premenopausal, premenopausal BC, case-control, and cohort studies as key words. Our paper follows the preferred reporting items for systematic reviews and meta-analysis (PRISMA) statement guidelines described by Liberati et al. [
Overweight and obesity are defined as abnormal or excessive fat accumulation that may impair health [
(a) Combined recommendations of body mass index and waist circumference cut-off points made for overweight or obesity, and association with disease risk. (b) World Health Organisation cut-off points and risk of metabolic complications.
Body mass index | Obesity class | Disease risk (relative to normal weight and waist circumference) | ||
---|---|---|---|---|
Men < 102 cm | Men > 102 cm | |||
Women < 88 cm | Women > 88 cm | |||
| ||||
Underweight | <18.5 | |||
Normal | 18.5–24.9 | |||
Overweight | 25.0–29.9 | Increased | High | |
Obesity | 30.0–34.9 | I | High | Very high |
35.0–39.9 | II | Very high | Very high | |
Extreme obesity | >40 | III | Extremely high | Extremely high |
Indicator | Cut-off points | Risk of metabolic complications |
---|---|---|
Waist circumference | Men > 94 cm; women > 80 cm | Increased |
Waist circumference | Men > 102 cm; women > 88 cm | Substantially increased |
Waist-hip ratio | Men ≥ 0.90 cm; women ≥ 0.85 cm | Substantially increased |
Most available studies and meta-analyses have focused on BMI as a marker of general obesity [
Selected characteristics of studies in postmenopausal women included in the paper.
First author, year, and country | Study design | Population | Cases/controls or P-years | Type of exposure | Range of exposure | RR (95% CI) | Variables of adjustment or comment |
---|---|---|---|---|---|---|---|
Lahmann 2004 |
BMI | Study center, age, educational attainment, | |||||
non-HRT | >30 versus <25 |
| |||||
Cohort | Caucasian | 1,405/103,344 | HRT | >30 versus <25 |
| ||
WHR | |||||||
non-HRT | >0.84 versus <0.73 | 0.94 (0.74–1.21) | |||||
HRT | >0.84 versus <0.73 | 0.85 (0.60–1.20) | |||||
Tehard 2006 |
Cohort | Caucasian | 860/41497 | BMI |
≥30 versus <18.5 |
|
FHBC, age at menarche, age at first birth, parity, history of benign breast disease, alcohol consumption, number of years of education, marital status, and physical activity |
Bardia 2008 |
Cohort | Caucasian | 2503/35941 | Weight at age 12 | Above versus average |
|
Age, education status, age at menopause, age at menarche, parity, age at first birth, BMI at age 18 years, OC, HRT, smoking, alcohol, and physical activity level |
Baer 2010 |
Cohort | Caucasian | 4974/188,860 | Body fatness |
|
|
Age, time period, parity/age at first birth, FHBC, personal history of benign BC, height, alcohol intake, OC use, birth weight, age at menopause, and HRT use |
Kuriyama 2005 |
Cohort | Asian | 65/9,666 | BMI | ≥30 versus <25 |
|
Age, smoking, alcohol, consumption of meat, fish, fruits, green or yellow consumption of bean-paste soup, type of health, parity, age at menarche, and age at FFT pregnancy |
Iwasaki 2007 |
Cohort | Asian | 441/55,537 | BMI | >30 versus <19 | 2.28 (0.94–5.53) | Age, area, number of births, age at first birth, and height |
Kawai 2010 |
Cohort | Asian | 108/10,106 | BMI | ≥25 versus <20 |
|
Age, education, smoking, alcohol, and time spent walking, Menstrual and reproductive factors, HRT, and FHBC |
Palmer 2007 |
Cohort | African-American | 455/59,000 | BMI at age 18 |
≥25 versus <20 |
|
Age, age at menarche, parity, age at first birth, and family history of breast cancer |
Friedenreich |
Case-control | Caucasian | 771/762 | BMI |
≥31.3 versus <24.1 |
0.99 (0.74–1.32) |
Age, total caloric intake, physical activity, educational level, HRT, diagnosed with benign BC, FHBC, alcohol, and current smoke |
Huang 1999 |
Case-control | Caucasian |
436/354 | WHR | >0.8 versus ≤0.8 |
|
Age at menarche, nulliparity, breastfeeding, Abortion or miscarriage, BMI, WHR, oral contraceptive, HRT, FHBC, smoking, alcohol, education, medical radiation to the chest |
BMI | |||||||
Black | 30.1–59.2 versus 14.6–24.6 | 0.68 (0.33–1.42) | |||||
Hall 2000 |
Case-control | Caucasian |
382/419 | White | 30.1–59.2 versus 14.6–24.6 | 1.08 (0.58–2.00) | Age, age at menarche, parity/age at FFT pregnancy, lactation, and education |
WHR | |||||||
Black | 0.86–1.34 versus 0.6–0.77 | 1.62 (0.70–3.79) | |||||
White | 0.86–1.34 versus 0.6–0.77 | 1.64 (0.88–3.07) | |||||
BMI at 18 years | ≥25 versus <20 |
|
|||||
Berstad 2010 |
Case-control | Caucasian |
1,900/2,006 | Recent BMI | Age, race, education, study site, FHBC, parity, age at menopause, and HRT | ||
Caucasian | ≥35 versus <25 | 0.75 (0.53–1.06) | |||||
African-American | ≥35 versus <25 | 1.26 (0.55–1.85) | |||||
Ogundiran 2010 |
Case-control | African | 498/266 | BMI | ≥28 versus <21 | 0.76 (0.48–1.21) | Age, ethnicity, education, menarche, parity, age at FFTP, breastfeeding, menopausal status, age at menopause, FHBC, benign breast disease, contraceptive, alcohol |
Adebamowo 2003 |
Case-control | African | 234/273 | BMI | ≥30 versus <20 | 1.82 (0.78–4.31) | Age, age at menarche, age at FFT pregnancy, height |
Wenten 2002 |
Case-control | Caucasian |
687/820 | BMI | Age; FHBC; total MET-hours; parity; OC; breastfeeding; age at first live birth; months of HRT use | ||
Caucasian | ≥30 versus <22 | 2.77 (0.86–8.89) | |||||
Hispanic | ≥30 versus <22 | 1.32 (0.47–3.72) | |||||
BMI non-HRT user | Age, center, physical activity level, energy intake, alcohol intake, age at menopause, parity, and Height | ||||||
Caucasian | >30 versus <25 |
| |||||
Slattery 2007 |
Case-control | Caucasian |
2,325/2,525 | Hispanic | >30 versus <25 | 0.80 (0.44–1.45) | |
WHR non-HRT user | |||||||
Caucasian | >0.9 versus <0.8 | 1.51 (0.93–2.46) | |||||
Hispanic | >0.9 versus <0.8 | 0.77 (0.39–1.50) | |||||
Ng 1997 |
Case-control | Asian | 130/585 | WHR | >0.86 versus <0.75 |
|
Age, menopausal status, age at menarche, parity, number of birth, age at FFT birth, HRT, OC, breast feeding, smoking, height, weight, and BMI |
Chow 2005 |
Case-control | Asian | 198/353 | BMI | 23–27 versus <19 |
|
Age, number of pregnancies, family history of breast cancer, income, smoking, alcohol, use of OC, and education |
Wu 2007 |
Case-control | Asian | 1,277/1,160 | BMI |
>24.60 versus ≤20.43 |
1.35 (0.95–1.93) |
Age, Asian ethnicity, duration of residence in the US, education, menarche, parity, menopausal status, age at menopause, intake of tea and soy, and physical activity |
Mathew 2008 |
Case-control | Asian | 968/691 | BMI | 25–29.9 versus <25 |
|
Age, center, religion, marital status, education socioeconomic status, residence status, parity, age at 1st childbirth, duration of breast feeding, and physical activity |
Connolly 2002 |
Meta-analysis | All | 19 studies | WHR | 0.1 unit increase |
|
A meta-analysis was done to summarize the literature on WHR and breast cancer risk published from January 1966 to August 2002 |
Harvie 2003 |
Meta-analysis | All | 8 studies: |
WHR | Lifestyles and reproductive factors (confounders that were found to be significant in proportional hazard regression analysis) | ||
Cohort studies | 0.75 versus 0.80 |
| |||||
Case-control studies | 0.75 versus 0.80 | 1.82 (0.85–3.85) | |||||
Suzuki 2009 Sweden [ |
Meta-analysis | All | 31 studies: |
BMI ER+PR+ | 0.5 unit increase |
|
Meta-analysis of cohort and case-control studies (from 1970 to 2007) was performed to clarify the association between body weight and the incidence of BC defined by ER/PR status of the tumors |
Van Den Brandt 2000 |
Meta-analysis | Caucasian | 4,385/337,819 | BMI | 21 versus 31 |
|
HRT, OC, history of benign breast disease, FHBC, smoking status, education, fat intake, fiber intake, energy intake, and alcohol intake |
Renehan 2008 |
Meta-analysis | Caucasian |
31 studies | BMI all |
5 units increase |
|
Cohort and case-control studies published from 1966 to November 2007 were included in the analysis. The dose response meta-analysis was adjusted by geographic region and cancer site |
Sarkissyan 2011 |
Cross- |
African-American |
237/234 | BMI | Age, ethnicity, comorbidity, and menopausal status | ||
African-American | ≥30 versus <25 | 4.8 (1.8–12.7) | |||||
Hispanic | ≥30 versus <25 | 1.4 (0.5–4.1) |
BMI: measurement of body mass index (in kg/m2); WHR: waist-hip ratio; ER: estrogen receptor; PR: progesterone receptor; BC: breast cancer; HRT: hormonal replacement therapy; OC: oral contraceptives; FFT: age at first full-term pregnancy; FHBC: family history of breast cancer; Y: years.
Bold: statistically significant.
Forest plot of the association between BMI and breast cancer risk in postmenopausal women. The size of each box indicates the relative weight of each study; the horizontal bars show the 95% confidence intervals (CI). RR: relative risk; 95% CI: 95% confidence intervals.
WHR is commonly used as a measure of central obesity [
Forest plot of the association between WHR and breast cancer risk in postmenopausal women. The size of each box indicates the relative weight of each study; the horizontal bars show the 95% confidence intervals (CI). RR: relative risk; 95% CI: 95% confidence intervals.
Previous studies, reviews, and pooled analyses have addressed the association of BMI and premenopausal BC (Table
Selected characteristics of studies in premenopausal women included in the paper.
Authors, years, and country | Study design | Population | Cases/controls or P-years | Type of exposure | Range of exposure | RR (95% CI) | Variables of adjustment or comments |
---|---|---|---|---|---|---|---|
Weiderpass et al., 2004 |
Cohort | Caucasian | 733/99,717 | BMI |
|
|
Age at enrolment, parity, age at FFT pregnancy, OC, age at menarche, FHBC, total duration of breast feeding, and country |
Lahmann et al., 2004 |
Cohort | Caucasian | 474/73,542 | BMI |
≥28.8 versus <21.5 |
0.82 (0.59–1.14) |
Study center, age, educational attainment, smoking, alcohol, parity, age at first pregnancy, age at menarche, and current pill use |
Baer et al., 2005 |
Cohort | Caucasian | 1,318/109,267 | Increase body fatness | Age, time period, birth weight, height, | ||
From age 5 to 10 | ≥2 levels versus no change |
|
|||||
From age 5 to 20 | ≥2 levels versus no change |
|
|||||
From age 10 to 20 | ≥2 levels versus no change |
|
|||||
Tehard and Clavel-Chapelon, 2006 |
Cohort | Caucasian | 275/20,068 | BMI |
>30 versus <18.5 |
|
FHBC, age at menarche, age at FFTP, parity, history of benign breast disease, alcohol consumption, education, marital status, and physical activity |
Baer et al., 2010 |
Cohort | Caucasian | 2,188/188,860 | Body fatness |
|
|
Age, time period, parity, age at first birth, FHBC, personal history of benign breast disease, height, alcohol intake, OC, and birth weight |
Harris et al., 2011 |
Cohort | Caucasian | 620/45,799 | WHR ER− | ≥0.84 versus <0.73 |
|
Age, height, history of benign breast disease, FHBC, age at menarche, age at FFTP, parity, OC, alcohol, and physical activity |
Kuriyama et al., 2005 |
Cohort | Asian | 33/5,214 | BMI | ≥29.9 versus <25 |
0.84 (0.24–2.88) |
Age, smoking, alcohol, consumption of meat, fish, fruits, green or yellow consumption of bean-paste soup, type of health, parity, age at menarche, and age at FFT pregnancy |
Iwasaki et al., 2007Japan [ |
Cohort | Asian | 441/55,537 | BMI | >30 versus <19 | 1.47 (0.53–3.47) | Age, area, number of births, age at first birth, and height |
Wu et al., 2006 |
Cohort | Asian | 104/11,889 | BMI |
>26.2 versus 21.6 |
1.90 (1.00–3.40) |
Age at enrollment, height, weight |
Kawai et al., 2010 Japan [ |
Cohort | Asian | 108/10,106 | BMI | ≥25 versus <20 |
|
Age, education level, smoking, alcohol, time spent walking, which are known or suspected risk factors for BC. Menstrual and reproductive factors, HRT, and FHBC |
Palmer et al., 2007 |
Cohort | African-American | 496/59,000 | BMI at age 18 years Current BMI |
≥25 versus <20 |
|
Age, age at menarche, parity, age at first birth, FHBC |
Enger et al., 2000 |
Case-control | Caucasian | 701/714 | BMI | Age at reference year, socioeconomic status, age at menarche, age at FFT, number of full-term pregnancies, months of breastfeeding | ||
ER+PR+ | >32.4 versus <17.36 | 1.11 (0.7–1.77) | |||||
ER+PR− | >32.4 versus <17.36 | 0.92 (0.34–2.47) | |||||
ER−PR− | >32.4 versus <17.36 | 1.07 (0.56–1.68) | |||||
Friedenreich et al., 2002 |
Case-control | Caucasian | 462/475 | BMI |
≥29.2 versus <23.1 |
0.69 (0.47–1.02) |
Age, total caloric intake, physical activity, educational level, HRT, diagnosed with benign BC, FHBC, alcohol, and smoking |
Magnusson and Roddam, 2005 |
Case-control | Caucasian | 1560/1548 | Body fatness at 10 Y |
Plump versus thin |
|
Age and recruitment, region, parity, age at first birth, height, OC, and alcohol |
Berstad et al., 2010 United States [ |
Case-control | Caucasian | 2,097/2,035 | BMI at 18 years |
≥25 versus <20 |
|
Age, race, education, study site, family history, parity, age at menopause, and HT use |
Wenten et al., 2002 |
Case-control | Caucasian |
687/820 | BMI | Age; FHBC; total MET-hours; parity; OC; breastfeeding; and age at first live birth | ||
Caucasian | ≥30 versus <22 | 0.71 (0.19–2.63) | |||||
Hispanic | ≥30 versus <22 | 1.64 (0.52–5.11) | |||||
Slattery et al., 2007 |
Case-control | Caucasian |
2,325/2,525 | Current BMI | Age, height, physical activity, energy intake, parity, alcohol consumption, age at first pregnancy, and center | ||
Caucasian | >30 versus <25 | 0.82 (0.58–1.17) | |||||
Hispanic | >30 versus <25 | 0.96 (0.63–1.46) | |||||
BMI at 30 years | |||||||
Caucasian | >30 versus <25 | 0.91 (0.52–1.60) | |||||
Hispanic | >30 versus <25 |
| |||||
John et al., 2011 |
Case-control | Caucasian |
672/808 | BMI all |
>30 versus <25 |
|
Age, country of birth, education level, FHBC biopsy-confirmed history of benign breast disease, age at menarche, parity, breastfeeding, alcohol, physical activity, daily caloric intake, and height. Analyses of all women combined were also adjusted for race/ethnicity |
Ng et al., 1997 |
Case-control | Asian | 74/297 | WHR | >0.86 versus <0.75 |
|
Age, menopausal status, age at menarche, parity, number of birth, age FFT birth, HR, OC, breast feeding, smoking, height, weight, BMI |
Chow et al., 2005 China [ |
Case-control | Asian | 198/353 | BMI | 27–31 versus <19 | 1.32 (0.39–4.43) | Age, number of pregnancies, FHBC, income, smoking, alcohol, use of OC, education |
Sangaramoorthy et al., 2011 |
Case-control | Hispanic | 210/265 | Weight at age 10 |
Heavier versus lighter |
0.63 (0.33–1.20) |
Age, country of birth, education, FHBC, prior biopsy-confirmed history of benign breast disease, parity, lifetime, breastfeeding, age at FFT, OC, adult height, alcohol consumption, and average caloric intake |
Huang et al., 1999 |
Case-control | Caucasian |
436/354 | BMI all |
>31 versus <31 |
1.00 (0.70–1.30) |
Age at menarche, nulliparity, breastfeeding, abortion or miscarriage, BMI, WHR, oral contraceptive, HRT, FHBC, smoking, alcohol, education, medical radiation to the chest |
Hall et al., 2000 |
Case-control | Caucasian |
390/319 | BMI | Age, age at menarche, parity/age at FFT pregnancy, lactation, education | ||
Black | 14.6–24.6 versus 30.1–58.2 | 0.89 (0.38–2.07) | |||||
White | 14.6–24.6 versus 30.1–58.2 |
|
|||||
WHR | |||||||
Black | 0.6–0.77 versus 0.86–1.34 |
|
|||||
White | 0.6–0.77 versus 0.86–1.34 |
|
|||||
Adebamowo et al., 2003 |
Case-control | African | 234/273 | BMI | ≥30 versus <20 | 1.21 (0.56–2.60) | Age, age at menarche, age at first pregnancy, height |
Ogundiran et al., 2010 |
Case-control | African | 707/820 | BMI | 31.2 versus <19.5 |
|
Age, ethnicity, education, age at menarche, number of live births, age at first live birth, duration of breastfeeding, menopausal status, FHBC, benign BC, OC, and alcohol |
Wu et al., 2007 |
Case-control | Asian | 1,277/1,160 | BMI |
>24.60 versus ≤20.43 |
|
Age, Asian ethnicity, duration of residence in the US, education, age at menarche, number of live births, menopausal status, intake of tea and soy during adolescence and adult life, and physical activity |
Ma et al., 2006 |
Case-control | Asian | 1,725/440 | BMI | ≥35 versus <25 |
|
Race, age, education, first-degree FHBC, age at menarche, gravity, number of full-term pregnancy, BMI 1 year before reference date, OC |
Mathew et al., 2008 India [ |
Case-control | Asian | 898/1,182 | BMI | 25–29.9 versus <25 |
|
Age, center, religion, marital status, education, socioeconomic status, residence status, parity, age at 1st childbirth, breast feeding, and physical activity |
Connolly et al., 2002 |
Meta-analysis | All | 19 studies | WHR | 0.1 unit increase |
|
A meta-analysis was done to summarize literature on WHR and breast cancer risk published from January 1966 to August 2002 |
Harvie et al., 2003 |
All | 8 studies: |
WHR | Lifestyles and reproductive factors | |||
Meta-analysis | Cohort studies | >0.80 versus <0.75 |
| ||||
Case-control studies | >0.80 versus <0.75 |
| |||||
Suzuki et al., 2009 |
Meta-analysis | All | 31 studies: |
BMI ER+PR+ | 5 units increase | 0.90 (0.82–0.99) | Meta-analysis of cohort and case-control studies (from 1970 to 2007) between body weight, and the incidence of BC defined by ER/PR status |
Van Den Brandt et al., 2000 |
Meta-analysis | Caucasian | 7 cohort studies | BMI | >31 versus <21 |
|
OC use, history of benign BC, FHBC, smoking status, education, fat intake, fiber intake, energy intake, and alcohol intake |
Renehan et al., 2008 |
Meta-analysis | Caucasian |
20 studies |
BMI (all) | 5 units increase |
|
Cohort and case-control studies published from 1966 to November 2007 were included in the analysis. The dose response meta-analysis was adjusted by geographic region and cancer site |
North American | 5 units increase |
|
|||||
European and |
5 units increase |
| |||||
Asia-Pacific | 5 units increase |
|
BMI: measurement of body mass index (in kg/m2); WHR: waist-hip ratio; ER: Estrogen receptor; PR: progesterone receptor; BC: breast cancer; HRT: hormonal replacement therapy; OC: oral contraceptives; FFT: age at first full term pregnancy; FHBC: family history of breast cancer; Y: years.
Bold: statistically significant.
Forest plot of the association between BMI and breast cancer risk in premenopausal women. The size of each box indicates the relative weight of each study; the horizontal bars show the 95% confidence intervals (CI). RR: relative risk; 95% CI: 95% confidence intervals.
WHR has not been consistently associated with increased BC risk in premenopausal women, for whom both null [
Forest plot of the association between WHR and breast cancer risk in premenopausal women. The size of each box indicates the relative weight of each study; the horizontal bars show the 95% confidence intervals (CI). RR: relative risk; 95% CI: 95% confidence intervals.
There is evidence suggesting that the waist-to-height ratio (WHtR) may be a more useful global clinical screening tool than WC, with a weighted mean boundary value of 0.5 [
The association between obesity and BC appears to vary according to the molecular subtype of BC, as defined by gene expression patterns into luminal A and B, HER2+, and triple-negative subtypes. A meta-analysis suggests that the association between BMI and BC risk is heterogeneous according to estrogen receptor (ER) and progesterone receptor (PR) status of the tumor. Higher BMI was associated with higher risk for ER+/PR+ tumors in postmenopausal women (RR = 1.82; 95% CI: 1.55–2.14) but had a protective effect on ER+/PR+ tumors in premenopausal women (RR = 0.80; 95% CI: 0.70–0.92). By contrast, no associations were observed for ER−PR− tumors [
In a pooled analysis of tumor marker and epidemiological risk factor data from 35,568 invasive BC case patients from 34 studies participating in the BC Association Consortium, obesity (BMI ≥ 30 kg/m2) in women ≤50 years was found to be more frequent in ER−/PR− than in ER+/PR+ tumors (
Most of the epidemiological studies have focused mainly on adult BMI and not on weight change or on the influence of early life body weight and body shape (silhouette). These factors, such as birth size, body shape, and weight during childhood or adolescence may play a role in the risk of BC. Epidemiologic studies have demonstrated that independently of BMI, greater body fatness during childhood or adolescence are associated with lower BC risk in both premenopausal women [
The complex associations between anthropometric measures of body fatness/obesity and the risk of BC suggest that metabolic conditions associated with high body fatness may influence this risk in several ways, with distinct effects on pre- and postmenopausal BC, as well as on different molecular subtypes of BC. It is now commonly accepted that the occurrence and development of BC is driven by the abnormal, clonal expansion of pools of initiated stem/progenitor cells [
Metabolic pathways linking obesity and breast cancer risk.
The above mechanisms are not mutually exclusive. They may operate in a complementary manner to promote specific forms of BC. One of the main paradox is the apparently opposite association of body fatness with pre- and postmenopausal BC. In Caucasians, most postmenopausal BC are ER+/PR+ (luminal A) subtypes and the effect of body fatness may involve increased hormone biosynthesis in adipose after the menopause, leading to the long-term maintenance of breast progenitor cells after the menopause. In contrast, in pre-menopausal women, the apparently protective effect of obesity may be due to hormone-independent forms of BC, which are more common among premenopausal women. Also, in premenopausal women estradiol levels are reduced in anovulatory cycles that are more frequent in obese than lean women. In addition, obese premenopausal women have been found to have reduced progesterone levels [
Obesity has become a crucial public health problem worldwide, especially for BC development and survival. Most studies have shown that BMI which reflects general obesity is associated with a decrease of the risk of developing BC before menopause and increase after menopause in most of the studies, while WHR which reflects central obesity is associated with an increased risk of both pre- and postmenopausal BC. Results are consistent with differences in metabolic risk and definitions of obesity according to ethnicity. Data regarding the relationship between obesity and young age and BC have demonstrated a strong inverse association between body fatness during childhood and adolescent and risk of BC throughout life in Caucasian population. The mechanisms for this inverse association are not fully understood and need further research. It will also be important to develop stringent recommendations and to maintain a healthy weight both at individual and community levels.
Body mass index
Breast cancer
Confidence interval
Estrogen negative
Hip circumference
Family history of breast cancer
Insulin-like growth factor 1
Odd ratio
Socioeconomic status
United States
Waist circumference
Waist hip ratio
World Health Organization.