Summary

Post-diagnosis weight gain is common in early-stage breast cancer and is associated with increased risk of recurrence and mortality. Intentional weight loss is difficult to maintain, and digital lifestyle interventions may provide a scalable approach to address this challenge. In this prospective single-arm study (ClinicalTrials.gov NCT04753268; February 15, 2021), key eligibility criteria included: stage I–III breast cancer, body mass index (BMI) ≥ 27.5 kg/m2, and completion of cancer treatment ≥6 months before study enrollment. Participants were provided with a behavioral change mobile application (Noom®). The primary endpoint was a change in self-reported weight from baseline to 26 weeks. Secondary endpoints included engagement, changes in physical activity, dietary patterns, and patient-reported outcomes (PRO). In total, 31 patients were enrolled (mean age 56.8 ± 9.9, mean baseline BMI 33.5 kg/m2 ± 6.5). The mean weight change was −4.8 kg ( ± 4.4, P < 0.001), mean percent weight change was −5.6% ( ± 5.0%); 11/31 patients (35.5%) lost ≥5% of their initial weight. Metrics of digital application engagement associated with weight loss ≥5% included articles read (P = 0.012), weights logged (P = 0.006), food records logged (P = 0.001), messages sent (P = 0.001), and application open count (P = 0.014). Significant increases were seen in mean daily step count (P = 0.004), GPAQ scores (P = 0.002), and Body Image Scale scores (P < 0.001). Mean energy intake remained consistently in a calorie-restricted range of 1300–1400 kcal/day. In this study, breast cancer survivors were highly engaged with a behavioral change smartphone application which led to clinically significant weight loss, increased physical activity, maintenance of an energy-restricted diet, and improvements in body image.