Magnitude and attributed reasons for adult weight gain amongst women at increased risk of breast cancer

doi:10.21203/rs.3.rs-1545605/v1

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Research Article

Magnitude and attributed reasons for adult weight gain amongst women at increased risk of breast cancer

https://doi.org/10.21203/rs.3.rs-1545605/v1

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Background: Excess weight (BMI ≥25.0 kg/m²) and weight gain during adult life increase the risk of postmenopausal breast cancer in women who are already at increased risk of the disease. Young adulthood (18-35 years) has previously been identified as the main time for weight gain in women. Reasons for weight gain in this population can inform strategies for weight gain prevention.

Methods: Baseline data from six weight loss studies for women at increased risk of breast cancer were collated. Self-reported patterns of adult weight gain and attributed reasons for weight gain before joining the weight loss study were reported for the whole population and secondary analyses reported the different reasons given by women with/without children, pre-/peri- or postmenopausal, and moderate/high risk of breast cancer.

Results: 521 women with a mean age of 47.6 (SD 8.2) years and median BMI of 30.2 (IQR 27.1-35.0) kg/m² were included in the analyses. The median weight gain since young adulthood (18-20 years) was 20.8 (IQR 14.2-30.0) kg or 33.9 (23.4-50.2) % and median annual weight gain was 0.74 (IQR 0.51-1.09) kg. 421 women were included in analysis of weight gain reasons. The main five self-reported reasons for weight gain were children / childcare / pregnancy (stated by 55.6% of participants), followed by inactivity (43.2%), comfort or boredom eating (38.2%), portion size (33.0%), and stress (27.3%). Reasons appeared broadly similar between the different groups in the secondary analyses.

Conclusions: We have highlighted common reasons for weight gain in women at increased risk of breast cancer. This will inform future interventions to support women to avoid weight gain in adulthood which would reduce the burden of breast cancer.

Trial registration: NIHR NRR N0226132725, ISRCTN52913838, ISRCTN77916487, ISRCTN91372184, ISRCTN10803394 and ISRCTN16431108.

breast cancer

weight gain

BMI

women

Excess weight (BMI ≥ 25.0 kg/m²)(1) and weight gain during adult life increases the risk of postmenopausal breast cancer (BC)(2, 3). Currently in England, 60% of adult women are overweight including 29% with obesity(4). BC is the most common cancer in women worldwide(5), and the second highest cause of cancer death in UK women(6). It is estimated that 8% of UK BCs are caused by overweight and obesity(7), equating to around 4,500 cases per year(6). Various groups have highlighted young adulthood (18–35 years) as the main time for weight gain in women (summarised in (8) and recent additional data from a large English cohort(9)). In addition to increasing risk of BC, weight gain during adulthood increases risk of diabetes, cardiovascular disease and other cancers in females(10).

A significant proportion of breast cancer cases, around 40%, are reported to occur in the 20% of women who are at increased risk (lifetime risk of BC ≥ 17% or 1 in 6 as defined by the Tyrer Cuzick model(11)). Targeting higher risk women with health behaviour interventions will have the biggest impact on reducing BC rates. Observational studies have reported that the relative risks of higher BMI and adult weight gain apply equally to women already at increased risk of the disease, i.e. with a family history or high polygenic risk score, compared to lower risk women(12–14). An Australian cohort study found that being overweight and obese is associated with a greater absolute increase in BC risk amongst women already at high familial risk compared with women from the general population. They concluded that “maintaining a healthy weight throughout adult life is of clinical significance for all women, and especially those with a family history of breast cancer”(15).

Many women known to be at increased risk of BC attend Family History, Risk and Prevention Clinics (FHRPCs) of which there are around 90 in the UK, including our own based at The Nightingale Centre, Manchester University NHS Foundation Trust (MFT). Analysis of BMI and health behaviour data from a sample of high risk women in our Manchester FHRPC (n = 136) highlighted the prevalence of unhealthy behaviours which were comparable to the general population, i.e. almost 60% had overweight or obesity, 30% did not meet physical activity (PA) recommendations, and 45% exceeded alcohol recommendations(16).

Since 2002 we have performed a number of weight loss intervention studies for women at increased risk of BC with BMI ≥ 24 kg/m² or weight gain > 10 kg since young adulthood. Findings of these studies have been published separately (Table 1). As part of the studies, baseline data was collected on 1) self-reported weight gain since the age of 18 or 20 years, and 2) women’s perceived reasons for this weight gain.

The aim of this paper is to report findings on the above two elements.

[INSERT TABLE 1]

Data source

The analysis used anonymised baseline data from six weight loss studies conducted at the FHRPC between 2002 and 2019 (Fig. 1, n = 521)(17–22). Inclusion criteria and details of ethics approvals and trial registry listings are given in Table 1.

Measures

Weight and height at study entry were measured as per standard protocols. Weight at age 18 or 20 was recalled by the participant. BMI at age 20 and entry was categorised as underweight (< 18.5 kg/m²), healthy weight (18.5–24.9 kg/m²), overweight (25.0–29.9 kg/m²), and obese (≥ 30.0 kg/m²)(1). Adult weight gain is calculated as the difference between weight at joining the study, and young adulthood weight (18 or 20 years depending on study). Annual weight change was calculated as weight change (kg) / duration between young adulthood weight and study entry (years). Weight loss was defined as a loss of 5% or more between young adulthood and study entry(23), weight maintenance as maintaining between +/-5% and the two weight gain categories were gaining 5-9.9%, or 10% or more. Participants reported their perceived opinions on reasons for weight gain using standard in-house questionnaires which included tick boxes for commonly occurring life events, psychological and physiological factors as well as actual diet and PA behaviours, with free text space for other reasons. Women could give more than one reason for weight gain. English Index of Multiple Deprivation was derived from postcodes(24).

Data Inclusion

We included women at increased risk of BC (i.e. ≥17% lifetime risk) and age ≥ 30 years as we were interested in weight gain from young adulthood. Analysis of weight gain reasons included women who had both gained ≥ 5% weight and given reasons for their weight gain. Two of the included studies also recruited women from outside of the FHRPC, but the majority of women recruited attended the Manchester FHRPC.

Statistical analysis

Descriptive statistics are presented with normally distributed data presented as mean (SD), otherwise median (IQR 25th -75th percentile) is used. Categorical data are presented as n (%). Reasons for weight gain are presented as a proportion of the included population stating each reason in descending order. Secondary analyses were run in sub-populations: those with / without children, pre / peri or postmenopausal at study entry, moderate risk of BC (17–30% lifetime risk) / high risk of BC (> 30% lifetime risk).

Included data are shown in Fig. 1. Women were excluded who were at low or average risk of BC (i.e. <17% lifetime risk, n = 104) aged and age < 30 years (n = 1). Uptake to and withdrawal from the included studies is described in the published papers(18–20, 25). Upon joining the weight loss studies, the population had a mean age of 47.6 (SD 8.2) years and a median lifetime BC risk of 1 in 3.5 (IQR 3.0-4.4) or 29 (23–33) %. They were predominantly of white ethnicity (96%) and from the two least deprived quintiles (54.3%, Table 2).

Table 2

Characteristics at young adulthood and joining weight loss study, and weight change between those times (n = 521)
	Young adulthood	At joining weight loss study
Age at joining weight loss study¹	-	47.6 (8.2)
Height (m)¹	-	1.64 (0.06)
Ethnicity² White Asian or Asian British Black or Black British Mixed Other	-	499 (95.8) 8 (1.5) 8 (1.5) 3 (0.6) 3 (0.6)
English Index of Multiple Deprivation quintile² 1 (most deprived) 2 3 4 5 (least deprived)	-	71 (13.6) 70 (13.4) 97 (18.6) 125 (24.0) 158 (30.3)
Premenopausal / Peri or postmenopausal²	-	283 (55.0) / 232 (45.0) Missing n = 6
Parous²	-	408 (79.1) Missing n = 5
Risk (1 in x)³	-	3.5 (3.0-4.4) Missing n = 13
Weight (kg)³	60.3 (54.0-66.7)⁴ Missing n = 33	82.1 (73.0–94.0) Missing n = 0
BMI (kg/m²)³	22.1 (20.4–24.1)⁴ Missing n = 33	30.2 (27.1–35.0) Missing n = 0
BMI categories²: Underweight (< 18.5 kg/m²) Healthy weight (18.5–24.9 kg/m²) Overweight (25–29.9 kg/m²) Obese (≥ 30.0 kg/m²)	34 (7.0) 363 (74.4) 67 (13.7) 24 (4.9)	0 (0.0) 37 (7.1) 218 (41.8) 266 (51.1)
Weight gain since young adulthood (kg)³	-	20.8 (14.2–30.0) Missing n = 33
Weight gain since young adulthood (%)³	-	33.9 (23.4–50.2) Missing n = 33
Duration between young adulthood weight and study entry (y)¹	-	27.8 (22.8–34.8)
Weight gain per year (kg)³	-	0.74 (0.51–1.09) Missing n = 33
Weight change category²: Lost ≤ 5% Maintained (within ± 5%) Gained 5-9.9% Gained ≥ 10%	-	6 (1.2) 7 (1.4) 10 (2.0) 465 (95.3) Missing n = 33
¹ mean (SD), ² n (%), ³ median (IQR: 25th and 75th percentiles), ⁴ young adulthood weight was self-reported

[INSERT Table 2]

In early adulthood (age 18–20 years), 74.4% had a healthy range BMI whilst only 7.1% were in the healthy BMI range at study entry (age 31–74 years, all ≥ 24 kg/m² as per eligibility criteria for the weight loss studies, Table 1). Only 2.6% (13/498) of the population either lost weight or maintained within ± 5% of their young adulthood weight while 95.3% gained ≥ 10% weight. The median annual weight gain was 0.74 (0.51–1.09) kg (Table 2).

Amongst participants who had gained ≥ 5% weight since young adulthood and provided reasons for weight gain (n = 421), the median number of reasons given per participant was 4 (IQR 2–6). Two thirds of women gave three or more reasons for their weight gain. The main reason given for weight gain was children / childcare / pregnancy (stated by 55.6% of participants), followed by inactivity (43.2%), comfort or boredom eating (38.2%), portion size (33.0%), and stress (27.3%, Table 3).

Table 3

Self-reported reasons for weight gain for women with weight gain of ≥ 5% weight in adulthood (n = 421)
Reason		Number stating reason	% stating reason
1	Children / Childcare / Pregnancy	234	55.6¹
2	Inactivity	182	43.2
3	Comfort or boredom eating	161	38.2
4	Portion Size	139	33.0
5	Stress	115	27.3
6	Marriage / settling down	101	24.0
7	Work / Study	86	20.4
8	Menopause / HRT	78	18.5²
9	Bereavement	77	18.3
10	Depression	65	15.4
11	Takeaways / Ready meals	63	15.0
12	Lack of time to prepare food	57	13.5
13	Alcohol	50	11.9
14	Food Preferences (own/family)	44	10.5
15	Giving up smoking	44	10.5
16	Health problems / Medications	38	9.0
17	Contraceptives	17	4.0
18	Cooking skills	12	2.9
19	Cost of healthy food	10	2.4
20	Eating out	6	1.4
21	Lack of sleep / tiredness	6	1.4
22	Carer	4	1.0
23	Fertility treatment	4	1.0
24	Social life / holidays	4	1.0
25	Sweet tooth	3	0.7
26	Divorce	2	0.5
27	Hysterectomy / oophorectomy	1	0.2
28	Appetite / Hunger	1	0.2
29	Premenstrual hunger	1	0.2
30	Progesterone replacement	1	0.2
¹ Includes all women but only n = 342 women known to have children. Of those with children, 234/342 (68.4%) gave Children / Childcare / Pregnancy as a reason for their weight gain.
² Includes all women but only n = 197 women known to be peri/postmenopausal women. Of peri/postmenopausal women, 96/197 (48.7%) gave menopause/HRT as a reason for their weight gain.
Excluding women missing percentage weight change (n = 33), women with percentage weight gain ≤ 5% (n = 6), and women not giving reasons for weight gain (n = 75): women could have been excluded for more than one of these reasons. Total excluded = 100. Participants could give multiple reasons for weight gain.

[INSERT Table 3]

For the sub-cohort with no children (n = 76), the most common reason for weight gain was inactivity (stated by 59.2%). Comfort or boredom eating, portion size, stress, and work / study as reasons for weight gain were all given by a higher proportion of women with no children compared to women with children (53.9% vs. 35.0%, 42.1% vs. 31.2%, 35.5% vs. 25.7%, 28.9% vs. 18.7% respectively) (Table 4).

Table 4

Self-reported reasons for weight gain for women with weight gain of ≥ 5% weight in adulthood: women with and without children
	Women with children (n = 343)		Women without children (n = 76)
Reason	Number stating reason	% stating reason	Number stating reason	% stating reason
Children / Childcare / Pregnancy	234	68.2	0	0.0
Inactivity	136	39.7	45	59.2
Comfort or boredom eating	120	35.0	41	53.9
Portion Size	107	31.2	32	42.1
Stress	88	25.7	27	35.5
Marriage / settling down	79	23.0	21	27.6
Work / Study	64	18.7	22	28.9
Menopause / HRT	62	18.1¹	16	21.1²
Bereavement	62	18.1	15	19.7
Depression	49	14.3	16	21.1
Lack of time to prepare food	46	13.4	11	14.5
Takeaways / Ready meals	46	13.1	17	22.4
Alcohol	37	10.8	13	17.1
Food Preferences (own/family)	36	10.5	8	10.5
Giving up smoking	33	9.6	11	14.5
Health problems / Medications	33	9.6	5	6.6
Contraceptives	15	4.4	2	2.6
Cost of healthy food	10	2.9	0	0.0
Cooking skills	9	2.6	3	3.9
Lack of sleep / tiredness	6	1.7	0	0.0
Eating out	3	0.9	3	3.9
Fertility treatment	3	0.9	1	1.3
Social life / holidays	2	0.6	2	2.6
Sweet tooth	2	0.6	1	1.3
Carer	1	0.3	3	3.9
Divorce	1	0.3	1	1.3
Hysterectomy / oophorectomy	1	0.3	0	0.0
Premenstrual hunger	1	0.3	0	0.0
Progesterone replacement	1	0.3	0	0.0
Appetite / Hunger	0	0.0	1	1.3
¹ Includes all women but only n = 160 women known to be peri/postmenopausal women. Of peri/postmenopausal women, 62/160 (38.8%) gave menopause/HRT as a reason for their weight gain.
² Includes all women but only n = 37 women known to be peri/postmenopausal women. Of peri/postmenopausal women, 16/37 (43.2%) gave menopause/HRT as a reason for their weight gain.
Excluding women missing percentage weight change (n = 33), women with percentage weight gain ≤ 5% (n = 6), women not giving reasons for weight gain (n = 75), women with unknown parity status (n = 5). Women could have been excluded for than one of these reasons. Participants could give multiple reasons for weight gain.

[INSERT Table 4]

For the sub-cohort who were peri/postmenopausal and who provided reasons for weight gain (n = 197), the proportion stating menopause / HRT as a reason for weight gain was 39.6% (Table 5). Peri/postmenopausal women were less likely to report children / childcare / pregnancy, work / study, and stress as reasons for their weight gain. For premenopausal women (n = 222), Menopause / HRT as a reason for weight gain had been replaced in the main ten reasons again by takeaways / ready meals.

Table 5

Self-reported reasons for weight gain for women with weight gain of ≥ 5% weight in adulthood: peri/post- and premenopausal women
	Peri/postmenopausal women (n = 197)		Premenopausal women (n = 222)
Reason	Number stating reason	% stating reason	Number stating reason	% stating reason
Children / Childcare / Pregnancy	96	48.7¹	128	62.2²
Inactivity	90	45.7	90	40.5
Menopause / HRT	78	39.6	0	0.0
Comfort or boredom eating	70	35.5	92	41.0
Portion Size	67	34.0	72	32.4
Stress	46	23.4	69	31.1
Marriage / settling down	44	22.3	57	25.7
Work / Study	32	16.2	57	25.7
Bereavement	30	15.2	47	21.2
Depression	29	14.7	36	16.2
Alcohol	29	14.7	21	9.5
Takeaways / Ready meals	26	13.2	37	16.7
Lack of time to prepare food	21	10.7	36	16.2
Health problems / Medications	20	10.2	18	8.1
Giving up smoking	19	9.6	25	11.3
Food Preferences (own/family)	17	8.6	27	12.2
Cooking skills	5	2.5	7	3.2
Eating out	4	2.0	2	0.9
Cost of healthy food	3	1.5	7	3.2
Lack of sleep / tiredness	3	1.5	3	1.4
Carer	3	1.5	1	0.5
Social life / holidays	3	1.5	1	0.5
Contraceptives	2	1.0	15	6.8
Sweet tooth	2	1.0	1	0.5
Fertility treatment	1	0.5	3	1.4
Appetite / Hunger	1	0.5	0	0.0
Divorce	0	0.0	2	0.9
Hysterectomy / oophorectomy	0	0.0	1	0.5
Premenstrual hunger	0	0.0	1	0.5
Progesterone replacement	0	0.0	1	0.5
¹ Includes all women but only n = 160 women known to have children. Of those with children, 96/160 (60.0%) gave Children / Childcare / Pregnancy as a reason for their weight gain.
² Includes all women but only n = 182 women known to have children. Of those with children, 138/182 (75.8%) gave Children / Childcare / Pregnancy as a reason for their weight gain.
Excluding women missing percentage weight change (n = 33), women with percentage weight gain ≤ 5% (n = 6), women not giving reasons for weight gain (n = 75), women with menopausal status unknown (n = 6). Women could have been excluded for than one of these reasons. Participants could give multiple reasons for weight gain.

[INSERT Table 5]

Comparison of weight gain reasons between women with moderate (lifetime risk of BC 17–30% and) versus high risk (> 30% lifetime risk) of BC showed that the proportions of women at moderate risk stating many of the reasons were higher than amongst women at high risk of BC (for example comfort or boredom eating 42.9 vs. 34.5%, portion size 38.1 vs. 29.1%) (Table 6). The main ten reasons for both groups differed only by the tenth reason which was depression for women at moderate risk, and takeaways / ready meals for women at high risk of BC.

Table 6

Self-reported reasons for weight gain for women with weight gain of ≥ 5% weight in adulthood: moderate and high risk of BC
	Moderate risk (17–30% lifetime risk) (n = 210)		High risk (> 30% lifetime risk) (n = 203)
Reason	Number stating reason	% stating reason	Number stating reason	% stating reason
Children / Childcare / Pregnancy	120	57.1¹	110	54.2²
Inactivity	90	42.9	89	43.8
Comfort or boredom eating	90	42.9	70	34.5
Portion Size	80	38.1	59	29.1
Stress	68	32.4	47	23.2
Work / Study	52	24.8	34	16.7
Marriage / settling down	48	22.9	51	25.1
Bereavement	46	21.9	31	15.3
Menopause / HRT	44	21.0³	31	15.3⁴
Depression	39	18.6	26	12.8
Lack of time to prepare food	36	17.1	21	10.3
Takeaways / Ready meals	35	16.7	28	13.8
Alcohol	31	14.8	19	9.4
Food Preferences (own/family)	31	14.8	13	6.4
Health problems / Medications	22	10.5	16	7.9
Giving up smoking	18	8.6	26	12.8
Cooking skills	7	3.3	5	2.5
Cost of healthy food	7	3.3	3	1.5
Contraceptives	7	3.3	10	4.9
Eating out	4	1.9	2	1.0
Lack of sleep / tiredness	3	1.4	3	1.5
Carer	3	1.4	1	0.5
Fertility treatment	3	1.4	1	0.5
Social life / holidays	2	1.0	2	1.0
Sweet tooth	2	1.0	1	0.5
Appetite / Hunger	1	0.5	0	0.0
Divorce	1	0.5	1	0.5
Hysterectomy / oophorectomy	1	0.5	0	0.0
Premenstrual hunger	0	0.0	1	0.5
Progesterone replacement	0	0.0	1	0.5
¹ Includes all women but only n = 176 women known to have children. Of those with children, 120/176 (68.2%) gave Children / Childcare / Pregnancy as a reason for their weight gain.
² Includes all women but only n = 161 women known to have children. Of those with children, 110/161 (68.3%) gave Children / Childcare / Pregnancy as a reason for their weight gain.
³ Includes all women but only n = 92 women known to be peri/postmenopausal women. Of peri/postmenopausal women, 44/92 (47.8%) gave menopause/HRT as a reason for their weight gain.
⁴ Includes all women but only n = 101 women known to be peri/postmenopausal women. Of peri/postmenopausal women, 31/101 (30.7%) gave menopause/HRT as a reason for their weight gain.
Excluding women with no % weight change (n = 33), women with % weight gain ≤ 5% (n = 6), women not giving reasons for weight gain (n = 75), women with unknown risk (n = 13). Women could have been excluded for than one of these reasons. Participants could give multiple reasons for weight gain.

[INSERT Table 6]

In this analysis of women at increased risk of BC who had joined weight loss studies in Manchester, most women gave multiple perceived reasons for their weight gain. The main causes of weight gain as perceived by the study participants were related to pregnancy and childcare, a lack of PA, and comfort and boredom eating. The predominant reasons for weight gain for sub-cohorts with/without children, pre/peri or postmenopausal and moderate/high risk of BC were broadly similar.

Our recent review of weight gain in 18–35 year old women highlighted many of the reasons also reported in the current analysis(8). Pregnancy and motherhood are amongst the life events associated with the largest amount of weight gain, with women in the UK weighing a mean of 3.5 (SD 6.2) kg heavier than their pre-pregnancy weight at 6 months postpartum (n = 12,583)(26). Motherhood is associated with a decrease in levels of PA(27, 28), mainly due to lack of time(29–31), which could contribute to further weight gain after pregnancy. This aligns with the current findings as children / childcare / pregnancy was the major reason given by women for their weight gain in both the whole cohort (56%) and the sub-cohort with children (68%). Inactivity was the next most cited reason by 43% of the whole cohort. Figures for England state that 34% of adult females (age 19–84) do not meet government guidelines for physical activity(32) (> 150 minutes of moderate or 75 minutes of vigorous intensity activity per week, or a combination of both) and a summary of evidence by the World Cancer Research Fund showed that there was convincing evidence that walking protects against weight gain and probable evidence for aerobic PA(33).

Thirty-three percent of women gave portion size as a reason for their weight gain. The link between portion size and weight gain is complex due the effects of other factors such as energy density and frequency of consumption, but reviews of the literature suggest that there is enough evidence to implicate portion size as an important component in the development of overweight and obesity(34, 35).

Finding effective ways to support women avoid weight gain during adulthood is a priority for women identified at increased risk of breast cancer. Our recent review summarised previous research into weight gain prevention interventions(8). Interventions based around pregnancy and postpartum have the strongest evidence base and a number of interventions could progress to practice. Evidence for interventions targeting other life events or general weight gain in young women is weaker and hampered by poor quality studies.

The strength of the current analysis is that combining data from a number of studies increased the sample size to over 500 women, with the majority (85%) providing reasons for weight gain.

There is likely to be an overlap between many of the reasons provided, i.e. inactivity is often attributed to lack of time which is commonly associated with motherhood and childcare(29–31). Lower PA is also associated with marriage and cohabiting in women(36, 37). Comfort or boredom eating (mentioned by 38% of the cohort) is often associated with stress (27%) and depression (15%)(38).

The generalisability of the findings to high risk populations is limited for a number of reasons. Women joined the included studies because they were interested in losing weight by joining dietitian-led weight loss programmes. The majority of participants were white and the population was skewed towards the least deprived quintile, as is a recognised problem in health research(39). Weight at study entry was reliably measured as per study protocols on calibrated scales, however weight in young adulthood was recalled therefore could be inaccurate, although studies have shown recalled weights to be fairly accurate on a population level(40). Providing tick box options could have been leading and altered results, for example attending university is often associated with weight gain in women(41, 42) but was not included in the tick boxes which may explain why it was not mentioned by any of the study participants. Primacy bias, where respondents are more likely to choose the first few response options when presented with a list, could also have affected the present results. Some of the sub-cohorts we analysed were small, for example there were only 76 women with no children.

Limiting weight gain that is frequently experienced by young women could reduce the burden of BC and other diseases. Our analysis has highlighted common reasons women at increased risk of BC attribute to their gain weight. This will help inform the design of future interventions to support women to avoid weight gain. Future research should focus on developing and testing such interventions thus reducing weight gain particularly in women identified at increased risk of BC which will lead to a reduction in the burden of BC.

Ethics approval and consent to participate: All studies were performed in accordance with the Declaration of Helsinki and relevant guidelines and regulations. All participants in the included studies provided informed consent. NHS Research Ethics Committee approvals for each study were as follows: Lifestyle: South Manchester REC (ref: 01/426), IER vs CER diets: Bolton (Lancashire) Local REC (ref: 05/Q1409/42), BRRIDE: North West 10 REC, Greater Manchester North (ref: 09/H1006/33), PROCAS-Lifestyle: NRES Committee West Midlands–Solihull (ref: 14/WM/1088), BRRIDE 2: NRES Committee South Central - Oxford B (ref: 14/SC/1097), Family History Lifestyle: North West - Preston Research Ethics Committee (ref: 17/NW/0440).

Consent for publication: Not applicable.

Availability of data and materials: The datasets analysed for this article are available in the Figshare repository (https://doi.org/10.48420/19614531.v1), apart from the Lifestyle Study for which the dataset is not publicly available as participants on this study did not consent to anonymous data sharing.

Competing interests: The authors declare that they have no competing interests.

Funding: Funding for the included studies is detailed in Table 1. None of the funding bodies played a role in the design of the study and collection, analysis, and interpretation of data or in writing this manuscript. MP and DGE are supported by the National Institute for Health Research (NIHR) Manchester Biomedical Research Centre (BRC1215-20007). The views expressed are those of the authors and not necessarily those of the NHS, the NIHR, or the Department of Health and Social Care.

Authors' contributions: Conception of the studies (MP, MH, DGE, AH), design of the work (MP, MH, EH), acquisition of data (MP, MH), analysis of data (MP), interpretation of data (MP, MH, EH), drafting the work (MP). All authors read and approved the final manuscript.

Acknowledgements: We thank the women who participated in, and the research staff who worked on the included studies.

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Table 1 is available in the Supplementary Files section

No competing interests reported.

Table1.xlsx
Table 1: Key information about the weight loss studies included in analyses

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Magnitude and attributed reasons for adult weight gain amongst women at increased risk of breast cancer

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Competing Interests

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