Time Restricted Eating and Cardiac Rehabilitation

Overview

This study will use a form of intermittent fasting called time-restricted eating (TRE) where individuals consume ad libitum energy intake within a set window of time, commonly 8 hours, which induces a fasting window of 16 hours per day (i.e., 16:8 TRE). TRE could be an effective addition to cardiac rehabilitation as it has demonstrated cardiovascular health benefits and potential for synergy when combined with exercise training. This study will determine if TRE is a feasible and safe nutrition intervention during cardiac rehabilitation and if TRE improves the health benefits of cardiac rehabilitation compared to cardiac rehabilitation alone.

HYPOTHESIS 1. Cardiac rehabilitation and TRE will be feasible in terms of adherence to a 16-hour daily fast (≥70%, which would represent 5/7 days/week) and safe (no excess symptoms or adverse events) 2. Cardiac rehabilitation and TRE will provide added cardiovascular health benefits (improved VO2peak, reduced fat mass) compared to cardiac rehabilitation alone. JUSTIFICATION: Past animal and human clinical trials have demonstrated TRE to be beneficial in realigning circadian rhythm, improve coronary artery disease (CAD) and peripheral artery disease (PAD) through the reduction in calorie intake, and promote cell signalling and repair pathways during the fasting period. TRE has not been tested in patients with CAD or other heart diseases but has shown to improve comorbid conditions (diabetes and hypertension) and improve metabolic profiles (blood pressure, hemoglobin A1c, fasting glucose, insulin sensitivity, and lipid profiles. Additionally, TRE when combined with exercise, such as in cardiac rehabilitation programs, improves VO2 peak and reduces fat mass compared to exercise alone. The proposed study will deliver a TRE intervention in combination with the cardiac rehabilitation program and is expected to be feasible, safe, and improve outcomes of cardiac rehabilitation. OBJECTIVES: The primary aim of this study is to evaluate the feasibility (adherence) and safety (adverse events) of TRE in combination with cardiac rehabilitation. The secondary aim is to assess the efficacy of the intervention on: 1. VO2peak, body composition, fasted glucose, hemoglobin A1c, blood pressure and waist circumference 2. Lifestyle behavioral change outcomes (dietary intake, dietary quality, physical activity, perceived stress) 4.Cardiac rehabilitation adherence Exploratory aims of the study include identifying sex differences (equal recruitment of males and females) and participants' experience with TRE (including confidence in maintaining this eating pattern or modifications to increase adherence). RESEARCH METHOD This study will be a two-site (Toronto Rehabilitation Institute and Toronto Western Hospital), 2-arm, parallel-group, randomized feasibility trial of cardiac rehabilitation alone or cardiac rehabilitation plus 16:8 TRE. Men and women who are referred through the standard clinical pathways for coronary artery disease and are willing to accept random assignment and complete the study assessments will be enrolled. Both groups will receive the standard, multi-dimensional cardiac rehabilitation program consisting of physician-directed risk factor management, an individualized exercise prescription, and virtual education. Participants randomized to the TRE group will be asked to eat only between 11 am and 7 pm for the duration of the cardiac rehabilitation program (\~16 weeks). Adherence will be collected via twice daily text messages asking participants to respond with the time they started and stopped eating. Safety will be collected by self-report and medical records. Efficacy outcomes will be assessed by cardiopulmonary exercise test, blood draw, dual x-ray absorptiometry, 3-day diet records, accelerometers, and questionnaires. Study outcomes will be measured at baseline and at the end of the cardiac rehabilitation program. SAMPLE SIZE A priori sample size for recruitment (n=60, 30 per group, equal recruitment of sex) was not fully achieved within the study period. Over the course of two years, the study efforts successfully recruited 30 male participants within the first 12 months of recruitment. Only 15 female participants were recruited after 2 years of recruitment efforts. The lower enrollment rate of females reflects both time limitations on the recruitment window and less females attending cardiac rehabilitation within the study criteria. The study team decided to end recruitment at n=45 (30 males, 15 females) after 2 years of recruitment due to personnel limitations STATISTICAL ANALYSIS Participant characteristics will be summarized using descriptive statistics. For adherence, both the text message response rate and adherence rate to the 16-hour daily fast will be reported. The change in caloric intake, diet quality, physical activity and efficacy outcomes will be compared between groups by analysis of covariance with baseline values as covariates. Relative risk will be used to compare the incidence of safety outcomes between groups. The primary analysis will be intention to treat and performed with both sexes combined. Secondary analyses will be performed separately in each sex.

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