Time-restricted Eating for Postpartum Weight Loss

Primary outcomes

1. Study Participation Rate

   Time frame: Baseline (6-16 weeks postpartum)

   Percentage of eligible subjects who agreed to participate out of those who were screened.

2. Oral Glucose Tolerance Test (OGTT)

   Time frame: Baseline (6-16 weeks postpartum), follow-up (18-28 weeks postpartum)

   Indices of glucose tolerance and insulin action will be assessed via a 2-hr OGTT. Participants will consume a 75-g glucose load within 5 minutes, which will be timed to begin at each participant's habitual breakfast time. Fasting blood samples will be collected at 15-, 30-, 60-, 90-, and 120-minutes relative to glucose consumption.

3. Energy Intake

   Time frame: Baseline (6-16 weeks postpartum), follow-up (18-28 weeks postpartum)

   Dietary intake will be collected at each assessment by 3 self-administered 24-hr recalls on 3 non-consecutive days (2 weekdays, 1 weekend day) using the Automatic Self-Administered 24-hour Dietary Assessment Tool (ASA24), an online platform developed and hosted by the National Cancer Institute. Total energy intake and kcals from each macronutrient will be derived from 24-hr recalls.

4. Participant Retention

   Time frame: Baseline (6-16 weeks postpartum), follow-up (18-28 weeks postpartum)

   The proportion of enrolled participants who complete follow-up.

5. Change in Visceral Fat

   Time frame: Baseline (6-16 weeks postpartum), follow-up (18-28 weeks postpartum)

   Bioelectrical impedance analysis (BIA) (seca® mBCA 514) will be used to assess visceral adipose tissue.

6. Participant Adherence to Intervention

   Time frame: Collected daily from intervention start (6-16 weeks postpartum) to follow-up (18-28 weeks postpartum)

   Adherence to eating window based on responses to daily electronic REDCap surveys that record start and stop time of the eating window.

7. eTRE Intervention Satisfaction

   Time frame: Baseline (6-16 weeks postpartum), follow-up (18-28 weeks postpartum)

   Participant satisfaction with the eating schedule will be assessed using a 5-point Likert scale. Long-term eating schedule preferences will be assessed by asking intervention participants at follow-up whether they plan to: (a) continue following the assigned eTRE schedule; (b) follow a modified eTRE schedule [and specifying what modifications they plan to make]; or (c) stop eTRE and return to prior meal timing habits.

   Qualitative data on eTRE intervention satisfaction will be collected at follow-up. These one-on-one interviews will be conducted in-person or remotely via videoconferencing. Topics explored will include participants' typical day during the intervention, experiences with eTRE, adherence barriers/facilitators, intervention satisfaction, and suggested improvements.

8. Change in Body Weight

   Time frame: Baseline (6-16 weeks postpartum), follow-up (18-28 weeks postpartum)

   Body weight measured at baseline and follow-up will be used to calculate weight change.

9. Change in Subjective Appetite

   Time frame: Baseline (6-16 weeks postpartum), follow-up (18-28 weeks postpartum)

   Subjective ratings of appetite (hunger and satiety) over the past week will be collected at baseline and follow-up using visual analogue scales scored from 0 (less hunger/less satiety) to 100 (more feelings of hunger/more feelings of satiety) based on the response along a 100-mm line.

10. Self-Reported Fatigue

    Time frame: Baseline (6-16 weeks postpartum), follow-up (18-28 weeks postpartum)

    Fatigue will be assessed using the NIH's validated 8-item Patient-Reported Outcomes Measurement Information System (PROMIS) Fatigue Short Form (SF) 8a to assess fatigue over the past 7 days. The PROMIS Fatigue SF 8a is scored on a T-score metric with a mean of 50 and standard deviation of 10. The T-score metric is referenced to the US general population with respect to race/ethnicity, age, education, and sex (e.g., T-score of 40 would be one SD below the US general population). A higher PROMIS T-score represents more of the concept being measured (higher score indicates more fatigue).