['Whether moderate to severe obesity (body mass index (BMI)≥30 to <40kg/m(2)) contributes to breast cancer recurrence and mortality remains uncertain.', '1199 women, recruited within 12 months of their diagnosis of hormone receptor positive (HR+), human epidermal growth factor receptor 2 negative (HER2-) invasive breast cancer completed an enrolment questionnaire and an annual follow-up questionnaire every 12 months for another 5 years. The impact of obesity on time to either local or distant recurrence or new breast cancer, or death due to breast cancer was determined by Cox regression. Women in the most extreme categories of BMI (<18.5 and ≥40) were excluded from the analysis.', 'Of the 1155 included women, mean age, 58.4±11.6 years, 53.8% had Stage 1 disease and 88.9% received oral adjuvant endocrine therapy (OAET) within 2 years of diagnosis. The likelihood of an event was significantly associated with moderate to severe obesity (HR=1.71, 95%CI, 1.12-2.62, p=0.014), disease beyond Stage 1 (HR=2.87, 95% CI 1.73-4.75, p<0.001), OAET (HR=0.26, 95%CI 0.14-0.46, p<0.001), mastectomy (HR=3.28, 95%CI 1.98-5.44, p<0.001) and radiotherapy (HR=2.12, 95%CI 1.24-3.63, p=0.006). For Stage 1 disease, only moderate to severe obesity (HR 3.23, 95%CI 1.48-7.03, p=0.003) and OAET use (HR 0.41, 95%CI 0.17-0.98, p=0.046) were significantly associated with an event.'] Is obesity associated with a poorer prognosis in women with hormone receptor positive breast cancer?