ImpRoving hEalth behaviourS for LIfe After ENdometrial CancEr Trial

Inclusion Criteria:

• ≥ 18 years old

• Histologically confirmed endometrioid adenocarcinoma (low-grade), FIGO 2009 stages Ito III.

• 1 month to 10 years post-surgery and completion of adjuvant treatment.

• BMI ≥25 and ≤45 kg/m2.

• Willing and able to adhere to the study interventions and assessments

• Seeking best weight using the readiness to change questionnaire.

• Have a cell phone compatible with the Fitbit app with internet access and Bluetoothcapabilities.

• Able to speak, read and understand English.

Exclusion Criteria:

• Recurrent (local, regional, or distant) or metastatic EC.

• Abnormal (i.e., mutated) p53 status in combination with FIGO 2009 stage III or IV

• Weight fluctuations (±5 kg) within the previous 3 months.

• Planned surgery in the next 6 months.

• Previous bariatric surgery.

• Uncontrolled thyroid disorder

• Type 1 diabetes.

• Type 2 diabetes with HbA1c > 10% or are taking insulin, sulfonylureas, or GLP-1agonists.

• Taking corticosteroids.

• Taking anti-obesity drugs.

• Current smoker (of any type, e.g e-cigarettes, tobacco, marihuana, vaping)

• Self-report >90 moderate-intensity min/week of aerobic physical activity on averageover the past three months.

• Potential safety risk with exercise or maximal exercise testing screened with the 2023 Physical Activity Readiness Questionnaire (PAR-Q+)53, signs and symptoms ofCVD, and any of the American Heart Association's absolute or relativecontraindications to exercise testing.

• Physical or mobility limitations impacting ability to perform physical activity.

• Self-report following a structured hypocaloric diet (e.g., using formulated mealreplacements, weight loss meal program) or a restrictive diet (intermittent fasting,or high-fat diet) in the past three months, or self-report currently following avegan diet but for less than two years.

• Self-reported history of an eating disorder diagnosed by a physician.

• Intending to be away longer than 2 weeks consecutively during the intervention andunable to adhere to the study protocol during this period.

• Active substance abuse (alcohol, cannabis, illicit drugs, prescription drugs).

• Dual-energy x-ray absorptiometry (DXA) or magnetic resonance imaging (MRI)contraindications for research purposes, such as pacemakers or pregnancy

• Unable to participate in telephone and virtual intervention protocols (e.g., havinga severe hearing or vision loss).

• Unable to adhere to the study protocol (i.e., unavailable to commit to scheduledgroup video conferencing sessions; limited access to the Internet; not willing touse platform, individuals who have been advised by a health professional not to loseweight or reduce caloric intake; cognitive impairment or dementia; etc.).

• Unable to come to study location.

• Unable to provide written informed consent.