Background: Overweight/obesity are strongly implicated in breast cancer development, and weight gain post-diagnosis is associated with greater morbidity and all-cause mortality. The aim of this study was to describe the prevalence of overweight/obesity and the pattern of weight gain after diagnosis of breast cancer amongst Australian women. Methods: We collected sociodemographic, medical, weight and lifestyle data using an anonymous, self-administered online cross-sectional survey between November 2017 and January 2018 from women with breast cancer living in Australia. The sample consisted mainly of members of the Breast Cancer Network Australia Review and Survey Group. Results: From 309 responses we obtained complete pre/post diagnosis weight data in 277 women, and calculated pre/post Body Mass Index (BMI) for 270 women. The proportion of women with overweight/obesity rose from 48.5% at diagnosis to 67.4% at time of survey. Most women were Caucasian with stage I-III breast cancer (n = 254) or ductal carcinoma in situ (DCIS) (n = 33) and mean age was 59.1 years. The majority of women (63.7%) reported they had gained weight after diagnosis with an average increase of 9.07 kg in this group. Of the women who provided complete weight data, half gained 5 kg or more, 17.0% gained > 20 kg, and 60.7% experienced an increase in BMI of >1 kg/m2. Over half of the women rated their concern about weight as high. Of those women who gained weight, more than half reported that this occurred during the first year after diagnosis. Two-thirds (69.1%) of women aged 35–74 years gained, on average, 0.48 kg more weight per year than age-matched controls. Conclusions: Although the findings from this survey should be interpreted cautiously due to a limited response rate and self-report nature, they suggest that women in Australia gain a considerable amount of weight after a diagnosis of breast cancer/DCIS (in excess of age-matched data for weight gain) and report high levels of concern about their weight. Because weight gain after breast cancer may lead to poorer outcomes, efforts to prevent and manage weight gain must be prioritized and accelerated particularly in the first year after diagnosis.
Keywords: Breast cancer; DCIS; Overweight; Obesity; Weight gain; Australian women; National survey; Prevalence
Breast cancer is the most common cancer in women worldwide and in Australia [[
Obesity at diagnosis is associated with worse BC survival and all-cause mortality rates and may increase the risk of cancer recurrence by 30–40% [[
The prevalence of weight gain after BC in Australia has not been adequately quantified. One prospective cohort study conducted in Queensland, in women who had been diagnosed with early breast cancer, described an increase in the proportion of women who were overweight/obese from 57% at diagnosis to 68% over 6 years [[
A cross-sectional self-administered anonymous survey was conducted in Australia between November 2017 and January 2018 using Qualtrics® online survey software [[
The survey was emailed to 1835 members on December 5th, 2017 and a reminder email sent January 15th, 2018 (Appendix). A smaller sample (n = 26) was also drawn from online communities (women's health organization social media pages and online breast cancer support groups in Australia) or through word of mouth during November and December 2017. Ethics approval for this study was provided by the Human Research Ethics Committee, Western Sydney University (H12444, October 2017).
The survey was developed after reviewing previous literature on weight after BC and was subsequently revised to include feedback from six BCNA representatives and several health researchers. The 60-item survey included questions on the sociodemographic characteristics, medical details such as diagnosis and treatment, lifestyle habits, weight status, and weight management. Details of the survey questions are outlined in the Appendix. In this paper, we report on change in weight from time of diagnosis to time of the survey.
Women were asked to self-report their weight in kg at the time of diagnosis, and current weight and height (in meters). Body Mass Index (BMI) was calculated from weight and height as weight/height
IBM SPSS® statistics package version 23 [[
We described the self-reported weight gain pattern as percentage of body weight at diagnosis, the proportion of women who gained
We calculated the mean weight gain per year in our sample as total weight gain divided by time since diagnosis in years. We removed one outlier who reported gaining 10.5 kg per year over 2 years and reported rate of weight gain across age groups in five-year brackets (see Fig. 3 and Table 5).
To compare weight gain in our sample against normative data in the Australian population, we used data the AusDiab study. The AusDiab study is a large national, longitudinal population-based study involving > 11,000 adults aged 25 years and older. Baseline data collection for the AusDiab study occurred during 1999–2000, with a subsequent 5-year follow-up (during 2004–2005) [[
Of the 1857 BCNA members, 283 (15%) responded to the survey. A further 26 women responded to the survey from other channels giving a total of 309 responses.
Demographic characteristics of respondents are described in Table 1. The majority of women were Caucasian (92.5%, n = 285) with a mean age of 59.1 years (SD = 9.5, range 33–78, n = 298). Characteristics were similar across BCNA members and non-BCNA respondents with no differences between these groups on Pearson's Chi-squared test. The majority of women were either premenopausal (43%) or perimenopausal (12%) at the time of diagnosis. Of the 145 women who were still menstruating at time of diagnosis, 68% were premenopausal and became postmenopausal, 18% were perimenopausal and became postmenopausal, while a smaller number (13%) remained perimenopausal.
Demographic characteristics of survey respondents
Description N (responses) % State ( Australian Capital Territory 14 4.5% New South Wales 91 29.5% Northern Territory 0 0.0% Queensland 48 15.5% South Australia 28 9.1% Tasmania < 5 1.0% Victoria 95 30.7% Western Australia 30 9.7% Education ( High school- year 10 30 9.8% High school- year 12 35 11.4% Vocational College 55 17.9% Bachelor's degree 90 29.3% Postgraduate degree 97 31.6% Ethnicity ( European/Anglo Saxon/Caucasian 285 92.5% Asian 5 1.6% Oceanic (incl. Australian and New Zealand first peoples, Polynesian and Micronesian) 13 4.2% North/South/Central American < 5 0.7% Mixed ethnicity < 5 0.7% Indian < 5 0.3% Employment ( Employee 140 45.5% Self-employed 33 10.7% Home duties/caring for children or family 15 4.9% In education (going to school, university, etc.) < 5 1.3% Doing voluntary work 10 3.3% Unable to work because of illness 6 2.0% Unable to work for other reasons < 5 0.3% Retired 99 32.1% Relationship Status ( Single 39 12.6% Married/de facto (living with partner) 230 74.4% In a relationship (not living with partner) 7 2.3% Divorced/separated 24 7.8% Widowed 9 2.9%
Clinical diagnoses of the respondents are summarized in Table 2. The majority of women (82%, n = 252) had been diagnosed with non-metastatic BC. The mean time since diagnosis of BC was 8.2 years (SD 5.12, range 1–32 years) and mean age at diagnosis was 50.9 years (SD = 9.02, range 29–74).
Diagnoses and treatments received
Description N % Missing n (%) Diagnoses 1 (0.3%) Ductal Carcinoma In Situ (DCIS) 33 10.7% Localised breast cancer 252 81.8% Metastatic breast cancer 14 4.6% Inflammatory breast cancer <5 0.7% Other including second primary 7 2.3% Treatment to the Breast 2 (0.6%) Lumpectomy alone <5 0.7% Lumpectomy and radiation 129 42.0% Mastectomy alone 74 24.1% Mastectomy and radiation 71 23.1% Lumpectomy and mastectomy alone 10 3.3% Lumpectomy, mastectomy and radiation 16 5.2% Double mastectomy 5 1.6% Reconstruction after mastectomy ( No 84 51.2% Immediate 37 22.6% Delayed 43 26.2% Treatment to the Axilla ( 13 (7.8%) Sentinel node biopsy only 24 15.6% Axillary dissection +/− Sentinel node biopsy 56 36.4% Axillary dissection +/− Sentinel node biopsy + radiation 72 46.8% Radiation only <5 1.3% Intravenous Systemic Therapy Chemotherapy without Herceptin 164 53.1% Herceptin only < 5 0.7% Chemotherapy + Herceptin 46 14.9% None/not reported 97 31.4% Hormonal Treatments Tamoxifen alone 58 18.8% Other 146 47.3% None 105 34.0% Current use of hormone therapy Yes 125 40.5%
Women reported receiving a range of BC treatments including surgery and/or radiation, and axillary, systemic and hormonal treatments, which are detailed in Table 2. The most commonly visited health care providers, within the last 12 months, were breast surgeons (n = 172), physiotherapists (n = 124) and medical oncologists (for chemotherapy) (n = 119). On average, respondents (n = 247) had visited three health care providers in the last 12 months (range, 1–10). For women with DCIS, 18 (53%) had a mastectomy, 17 (50%) had received radiation and 19 (56%) had received hormonal treatment.
Table 3 and Fig. 1 describe weight and BMI change patterns in our respondents. Mean self-reported weight at time of diagnosis was 71.24 kg (SD 14.01, range 47–158, n = 277) and at time of survey was 76.08 kg (SD 15.37, range 46–150, n = 293). Mean self-reported current BMI was 28.02 kg/m
Weight change patterns after diagnosis of breast cancer
Description N % Missing N (%) Self-reported weight gain pattern 17 (5.5%) Weight gain 186 63.7% Weight loss 38 13.0% Stable 48 16.4% Fluctuated 20 6.9% Calculated % weight change from baseline 32 (10.4%) Weight loss 62 22.4% <5% weight gain 53 19.1% 5–10% weight gain 64 23.1% >10% weight gain 98 35.4% Calculated weight change 32 (10.4%) Weight loss 62 22.4% Weight gain up to 5 kg 75 27.1% Weight gain ≥5 kg and < 10 kg 75 27.1% Weight gain ≥10 kg and < 20 kg 18 6.5% Weight gain 47 17.0% Timing of weight gaina ( <6 months post diagnosis 47 25.3% 6–12 months post diagnosis 60 32.3% 12–18 months post diagnosis 38 20.4% 18–24 months post diagnosis 16 8.6% 2–3 years post diagnosis 14 7.5% >3 years post diagnosis 11 5.9% Change in BMI classification from time of diagnosis to time of survey ( Weight gain Healthy to overweight 49 18.2% Overweight to obese 40 14.8% Healthy to obese 5 1.9% Underweight to healthy weight <5 1.5% Underweight to overweight <5 0.4% Stable Remained in healthy range 69 25.6% Remained in overweight range 39 14.4% Remained in obese range 40 14.8% Remained in underweight range 8 3.0% Weight loss Healthy weight to underweight 3 1.1% Obese or overweight to healthy weight 6 2.2% Overweight to underweight <5 0.4% Obese to overweight 5 1.9%
Graph: Fig. 1 Change in BMI classification after diagnosis of breast cancer. BMI=Body Mass Index
One fifth (54/270, 20.0%) of women went from being in the healthy weight range at diagnosis (BMI <25), to an unhealthy weight range (BMI
There was a statistically significant difference between both weight and BMI at diagnosis and current weight and BMI (mean difference 4.50 kg, CI 3.45–5.55, p = 0.00, n = 277 and 1.64 kg/m
Of the women who reported gaining weight overall and for whom we had complete weight data (n = 175), 87.4% (153/175) gained ≥5 kg of weight, and 54.9% gained > 10% of pre-diagnosis body weight. Average weight gain in this group was 9.07 kg. Women reported that weight gain predominantly occurred within the first 2 years of diagnosis (86.6%) with 57.5% reporting that weight gain mostly occurred within the first 12 months. Weight gain was not correlated with time since diagnosis (n = 173, r =.114, p = 0.14). There was no difference in the amount of weight gain by time since diagnosis when this was examined in blocks of 2.5 years, in women who had reported weight gain overall (n = 175, p = 0.26), and in women who self-reported weight gain of greater than 5% of diagnosis body weight (n = 162, p = 0.27). (Table 4).
Weight gain by time in years since diagnosis
Women who had gained >5% weight ( Women who reported weight gain pattern overall ( Mean weight gain (kg) SD Freq. Mean weight gain (kg) SD Freq. Time since diagnosis (years) < 2.5 9.00 (6.51) 6 8.14 (6.36) 7 2.5–5 8.42 (4.57) 23 7.36 (4.73) 28 5–7.5 9.27 (5.27) 54 8.90 (5.47) 56 7.5–10 9.15 (5.42) 22 8.43 (5.64) 24 > 10 11.21 (7.14) 57 10.38 (7.37) 60
SD Standard Deviation, Freq Frequency
Three quarters (74.7%, n = 68/91) of women who were currently obese reported very high levels of concern about their weight, compared to a quarter of women in the healthy weight range (25.9%, n = 21/81) (p = 0.00). Women who had gained more weight were more likely to express high levels of concern about their weight. Of the women who gained 5–10% of weight and > 10% of weight, 54.8 and 78.4% reported being very concerned about their weight respectively, compared with 22.5% of women who had gained less than 5% of their diagnosis weight (X
Graph: Fig. 2 Weight gain concern and current BMI classification (n = 285). BMI=Body Mass Index
On average, women in our study gained 0.64 kg per year (n = 270, SD = 1.76, range − 8 to 10.5) (see Table 5). For women aged 25–74 years (the age range for which we have normative data), the mean weight gain in excess of age-matched controls was 0.48 kg per year (n = 235, SD = 1.67, range − 8.38 to 7.62). Overall, two thirds (69.8%) of women in our sample gained in excess of normative weight gain in the AusDiab study, including 25.1% of women who gained > 1 kg per year in excess of normative rates of weight gain. There was no difference between age groups with regard to the number of women who gained in excess of normative weight gain (X2, (n = 235) = 6.6929, p = 0.153). See Fig. 3 for mean weight gain in excess of normative data for each age group. There was only one woman in the 25–34 age group; to protect confidentiality we did not include her data in Table 5 or Fig. 3.
Mean weight gain per year in each age group, and proportion who gained in excessive of normative rates
Age (years) Mean weight gain per year in kg in our study (SD) % who gained in excess of AusDiab data 35–44 ( 1.59 (1.16) 81.0 45–54 ( 0.75 (2.35) 61.1 55–64 ( 0.50 (1.47) 76.0 65–74 ( 0.39 (0.94) 64.3 All ( 0.64 (1.76) 69.8
Graph: Fig. 3 Mean weight gain per year in excess of normative data, by age (n = 234)
This is the first national survey conducted in Australia to describe weight after breast cancer. The distribution of responses according to state and territory in our survey is broadly consistent with the incidence of BC in these regions [[
The proportion of women who were overweight or obese in our study is consistent with those from a prospective study of 287 women conducted in Queensland, Australia which compared weight gain after diagnosis of early BC. By 6 years, 68% of women in the cohort were overweight or obese, [[
A large international review found that 50–96% of early stage BC patients experience weight gain during treatment in the range of 1.7 kg to 5.0 kg in the 18 months following treatment [[
Our findings are of concern because weight gain pre- and post- BC diagnosis have both been associated with increased morbidity and mortality. Whilst those at heaviest weight at diagnosis appear to carry an increased risk, even those within the healthy weight range at diagnosis face increased risk following weight gain [[
Our findings indicate high levels of concern about weight, particularly in women who were currently overweight or obese. Weight gain exacerbates the significant body image concerns already faced by BC survivors, has a negative impact on quality of life, and may be a cause of distress if it was unanticipated [[
Although the proportion of overweight and obesity in our survey is similar to national data for women aged 45–64 (which ranges from 61 to 69%) [[
This study also highlights the importance of treatment teams being aware that weight gain, particularly in the first year after treatment, is an important issue, which would benefit from interventions such as diet and exercise. In this study, 186 of 292 patients (63.69%) gained weight, 57% gained within the first 12 months and 77% within 18 months. The timing of weight gain within the first year of treatment has been reported by others [[
Strengths of this survey include the higher than expected response rate from the BCNA Review and Survey Group. According to the Research and Evaluation Manager, BCNA (email communication 3 Oct 2017), the typical response rate in this group is 10%, whereas the response to our survey was 15%. However, given that the Review and Survey Group represents only approximately 2% of all BCNA members, the validity of our findings is somewhat limited but important to highlight particularly to clinicians managing patients with breast cancer to ensure they encourage and more importantly "prescribe" an exercise program after cancer treatment.
We achieved a broadly nationally representative sample according to location. The percentage of respondents from each Australian State and Territory is similar to national averages on BC incidence as described by the Australian Institute of Health and Welfare cancer data [[
Limitations of this survey included its self-report nature. In general, people tend to underestimate their weight and overestimate their height with self-reporting [[
We acknowledge that the inability to provide matched controls in this survey is a limitation. However, we were able to retrospectively match women by age to controls from the 2005 AusDiab study and found that women gained in excess of normative data, although limitations of our comparison is that we could not locate more recent data on normative rates of weight gain, and the duration of weight gain varied in our sample. Furthermore, that our findings are remarkably similar to a cohort study in the state of Queensland in Australia [[
We were unable to report on the proportion of fat mass gained relative to muscle mass lost, know as sarcopenia. Sarcopenia is common in many women even without body weight change, with 74% of women increasing total body fat relative to lean muscle, [[
Another potential weakness of our study is that the vast majority of survey respondents were Caucasian, thereby limiting the generalizability of our data to women from other ethnicities but provides an important perspective over and above the Shanghai study where patients were less overweight or obese at diagnosis and whose diet differed from a Western diet. Previous research from the United States, has shown when compared with non-Hispanic whites, Hispanic and black women have higher rates of obesity (21.8%, compared with 29.4 and 39.2%, respectively), lower rates of meeting physical activity guidelines (19.0%, compared with 12.5 and 17.5%, respectively), and lower intake of three or more servings of fruit and vegetables per day (27.7%, compared with 19.7 and 21.9%, respectively). Understanding this in the Australian context will be an important component of future research [[
Additionally, although the response rate from the BCNA Review and Survey Group was higher than what is typically seen, this represented a very small proportion of all BCNA members, limiting the validity of our findings. Notwithstanding such limitations, the demographics in our sample (who were predominantly well-educated and either employed or self-employed) are not inconsistent with national data indicating that the incidence of breast cancer is highest in the areas with highest socioeconomic advantage [[
This is the first national survey of Australian women to describe weight gain after diagnosis of BC. Survey respondents gained a subtantial amount of weight (mean of 9.07 kg), with a doubling of the proportion of women living with obesity. This is coupled with high rates of concern about weight after breast cancer. Given that weight gain after BC may lead to poorer outcomes, there is a need to prioritize and accelerate efforts to assist women to prevent and manage weight gain after BC, particularly during the first 12 months after diagnosis.
This study did not receive any funding. CE is supported by an endowment from the Jacka Foundation of Natural Therapies.
We thank the consumer representatives from Breast Cancer Network Australia who provided feedback on the survey instrument used in this study; Natalie Zakhary who assisted with formatting the online survey and Karen Monaghan who assisted with data cleaning.
Participants in this research were recruited from Breast Cancer Network Australia's (BCNA) Review and Survey Group, a national, online group of Australian women living with breast cancer who are interested in receiving invitations to participate in research. We acknowledge the contribution of the women involved in the Review and Survey Group who participated in this project. Part of this manuscript has previously been presented at the Australian New Zealand Obesity Society/Australasian Society for Lifestyle medicine and International Chair on Cardiometabolic Risk (ANZOS-ASLM-ICCR) Annual Scientific Meeting in 2019 (
CE conceived of the study, designed the survey instrument, and collected the data. JB and KB contributed to design of the survey instrument and study. AEC led the data analysis. DN contributed significantly to interpretation of the data, drafting of the manuscript, and critical revision for important intellectual content. CE, AEC, JB, KB and DN contributed significantly to the interpretation of the data, drafting the manuscript, critical revision of the manuscript for important intellectual content, and provided final approval for publication.
The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.
Consent was implied upon commencing the online anonymous survey. Ethics approval was provided by the Human Research Ethics Committee, Western Sydney University (H12444, Oct 2017).
Not applicable.
The authors declare that they have no competing interests.
State of residence, highest level of education, ethnicity, employment status, relationship status, current age and age at diagnosis were included to describe the characteristics of women.
Women were asked about their diagnosis, treatments received including treatments received to the axilla, the number of lymph nodes removed, whether they had a reconstruction, use of hormonal treatments, menopausal state (at diagnosis and current), presence of other medical conditions and symptoms such as hot flushes and the presence and severity of lymphoedema.
Women were asked to describe the type of breast cancer they were diagnosed with as either "ductal cancer in-situ (DCIS)", "localised stage breast cancer (where your breast cancer is contained within your breast and/or lymph nodes), "metastatic breast cancer (breast cancer that has spread beyond the breast tissue and lymph nodes to distant parts of the body, such as the bones, liver and lungs; also called advanced, secondary or stage four) " or "inflammatory breast cancer. "For convenience, inflammatory breast cancer and metastatic breast cancer were then combined and referred to as advanced breast cancer. Women were also asked to indicate the treatments they received such as "Lumpectomy alone", "Lumpectomy and radiation", "mastectomy alone", "mastectomy and radiation", "removal of lymph nodes", "chemotherapy", "hormonal therapy", "targeted therapy (Herceptin)", and "other". As chemotherapy is invariably not provided to women with DCIS, we recoded the diagnosis as "localised" if a woman indicated that she had received chemotherapy.
Menopausal state at the time of diagnosis was assessed as either "Premenopausal (regular periods with no menopausal symptoms such as hot flushes)", "Perimenopausal/in the menopausal transition (no periods for at least 2 months, plus hot flushes)", "Postmenopausal (no periods for at least 12 months)" or "Previous surgical menopausal (both ovaries or uterus/womb had been removed)." Participants who indicated they were premenopausal or perimenopausal at the time of diagnosis were asked if they were having periods before breast cancer treatment and to describe what has happened to their periods now; "they have stopped", "they stopped and then started again", "they have become more irregular", "no change" or "other".
Lymphoedema severity was defined as either "no problem (no noticeable swelling)", "mild (soft swelling that is not obvious to others and comes and goes)", "moderate (swelling with occasional hardness in some areas that is obvious to others and is always present)", "severe (profuse swelling with thickened skin, constant hardness, and a very large, heavy arm that is extremely obvious to others and is always present) as described elsewhere [[
Women were asked if they had tried the following specific diets in the previous 12 months: Atkins diet (low carbohydrate), 5:2 diet (eat what you want 5 days a week, send your body into starvation mode for 2 days), Paleolithic diet, Dukan diet (High-protein, low-carb), Vegetarian diet, Vegan diet, Weight Watchers diet, Raw food diet, Ultra low-fat diet, Zon diet, Cambridge diet (very low calories), South Beach diet (low-GI), Other. They were asked if they ate at least the recommended serves of fruit and vegetables a day (2 fruit, five vegetable) with answer options of Yes/No. Self-perceived diet quality was assessed as Excellent/Very Good/Good/Fair/Poor. Smoking was assessed as current cigarrete use (Never smoked/Ex smoker/Recently quit ex smoker (smoked in the last 3 months)/Current smoker) and current smokers were asked to indicate the number of cigarettes they smoked each day. Alcohol intake was assessed as Non drinker/1–7 standard drinks a week/8–14 standard drinks a week/> 14 standard drinks a week) and a guide to standard drink sizes was provided. The validated Weight Self Efficacy Scale (WEL-SF) [[
Weight management.
Experiences with a range of weight loss interventions (Exercise, Diet – various: Intermittent fasting, etc. (please specify), Meal replacements e.g. shakes, Medication, Weight loss supplements/products, Surgery (please specify), Online program e.g. 12 week Body Transformation, Social support, Weight loss program e.g. Jenny Craig, Psychological treatments such as CBT (Cognitive Behavioural Therapy) and the perceived effectiveness of the interventions on was described using a five-point Likert scale from 1 (not at all effective) to 5 (very effective). The responses were further dichotomized into 1 to 2 (not effective) and 3 to 5 (effective). Women were also asked about perceived barriers and facilitators to successful weight loss and weight maintenance, and what they believed should be research priorities in this area.
• BC
- Breast Cancer
• BCNA
- Breast Cancer Network Australia
• BMI
- Body Mass Index
• DCIS
- Ductal Carcinoma In Situ
• GP
- General Practitioner
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