Study Overview
Objective. To compare the effects of intermittent energy restriction (IER) with those of continuous energy restriction (CER) on blood pressure control and weight loss in overweight and obese patients with hypertension during a 6-month period.
Design. Randomized controlled trial.
Settings and participants. The trial was conducted at the Affiliated Hospital of Jiaxing University from June 1, 2020, to April 30, 2021. Chinese adults were recruited using advertisements and flyers posted in the hospital and local communities. Prior to participation in study activities, all participants gave informed consent prior to recruitment and were provided compensation in the form of a $38 voucher at 3 and 6 months for their time for participating in the study.
The main inclusion criteria were patients between the ages of 18 and 70 years, hypertension, and body mass index (BMI) ranging from 24 to 40 kg/m2. The exclusion criteria were systolic blood pressure (SBP) ≥ 180 mmHg or diastolic blood pressure (DBP) ≥ 120 mmHg, type 1 or 2 diabetes with a history of severe hypoglycemic episodes, pregnancy or breastfeeding, usage of glucagon-like peptide 1 receptor agonists, weight loss > 5 kg within the past 3 months or previous weight loss surgery, and inability to adhere to the dietary protocol.
Of the 294 participants screened for eligibility, 205 were randomized in a 1:1 ratio to the IER group (n = 102) or the CER group (n = 103), stratified by sex and BMI (as overweight or obese). All participants were required to have a stable medication regimen and weight in the 3 months prior to enrollment and not to use weight-loss drugs or vitamin supplements for the duration of the study. Researchers and participants were not blinded to the study group assignment.
Interventions. Participants randomly assigned to the IER group followed a 5:2 eating pattern: a very-low-energy diet of 500-600 kcal for 2 days of the week along with their usual diet for the other 5 days. The 2 days of calorie restriction could be consecutive or nonconsecutive, with a minimum of 0.8 g supplemental protein per kg of body weight per day, in accordance with the 2016 Dietary Guidelines for Chinese Residents. The CER group was advised to consume 1000 kcal/day for women and 1200 kcal/day for men on a 7-day energy restriction. That is, they were prescribed a daily 25% restriction based on the general principles of a Mediterranean-type diet (30% fat, 45-50% carbohydrate, and 20-25% protein).
Both groups received dietary education from a qualified dietitian and were recommended to maintain their current daily activity levels throughout the trial. Written dietary information brochures with portion advice and sample meal plans were provided to improve compliance in each group. All participants received a digital cooking scale to weigh foods to ensure accuracy of intake and were required to keep a food diary while following the recommended recipe on 2 days/week during calorie restriction to help with adherence. No food was provided. All participants were followed up by regular outpatient visits to both cardiologists and dietitians once a month. Diet checklists, activity schedules, and weight were reviewed to assess compliance with dietary advice at each visit.