Fiber and Cardiovascular Risk Factors

Overview

This study was a parallel randomized controlled feeding trial conducted in overweight and obese participants who were attending the Nutrition Clinic in Isfahan, Iran. Inclusion criteria were as follows: women aged 18 to 50 years; body mass index (BMI) 25 kg/m2 ; having noncommunicable diseases such as diabetes, hyperlipidemia, and hypertension; having no history of liver and renal disease, hormonal disorders, food allergy, and other special diseases; not taking specific medications affecting weight; willingness to introduce a dietary change to lose weight; and habitual daily consumption of fruits, vegetables, and whole grains. The exclusion criteria were the following: weight loss of more than 10% of body weight within the 6 months before registration in the study; attending a competitive sport; no consumption of fruits, vegetables, or whole grains habitually; abnormal thyroid hormone concentration; intake of drugs or supplementation that could affect energy expenditure or weight; and not following recommended diets or returning for following visits. Recruitment ran from January 2016 to July 2016. The sample size was calculated based on the standard formula (45): by considering the Type 1 error (a) of 0.05 and Type 2 error (b) of 0.20 (power D 80%). Based on a previous study in Iranian women (46), we used a within-group BMI mean difference (d) of 2.5 kg/m2 and a standard deviation (SD) of 3.2 kg/m2 * Therefore, we needed 25 participants in each group. The study was approved by the research council and ethical committee of the School of Nutrition and Food Science, Isfahan University of Medical Sciences, Isfahan, Iran (grant number: 194172). All participants gave written consent before study enrollment. This trial was registered at ClinicalTrial.gov with code NCT03340298. Study design and interventions A randomized feeding trial was designed that aimed to compare the effect of different sources of fibers with low-calorie conventional diets on weight loss, waist circumference (WC), blood pressure, fasting blood glucose (FBS), and lipid profiles in overweight and obese women. Eligible participants were randomly assigned to the three groups after baseline measures of BMI, using a computer-generated random numbers method of randomization. Seventy-five participants who were eligible for the study were randomly divided to one of the three groups ("whole grains" high fiber diet, "fruits and vegetables" high fiber diet, and diet containing "whole grains, fruits, and vegetables") in a 1:1:1 allocation (Figure 2). Participant allocation was stratified by age and BMI. All participants consumed 35 g of fiber per day as follows: in the whole grains group (n D 25), 25 g of fiber from whole grain products and 10 g fiber from fruits and vegetables was to be consumed with the main meals; in the fruits and vegetables group (n D 25), 25 g of fiber from fruits and vegetables and 10 g from whole grain sources was to be consumed with the main meals; and in the whole grains, fruits, and vegetables group, participants were to consume an equal amount of fiber from both sources (17.5 g fiber from whole grains and 17.5 g fiber from fruits and vegetables) with their main meals daily for 10 weeks. The main meals were determined by an expert dietitian, based on the Harris-Benedict formula, considering 0.5 kg weekly weight loss for each participant. The distribution of macronutrients was similar among groups (carbohydrates, 55%; fat, 30%; and protein, 15%) and the number of servings of each food group was estimated and given to participants. Participants in each group were given their allowed food that contained a list of exchangeable foods, food groups, and subgroups (Table 2). All participants were instructed to attend the nutrition clinic to take their intended products. Participants were supplied with the fruits, vegetables, and whole grains for their diet and they consumed these food items under supervision in the nutrition clinic for 10 weeks. Other components of their weight loss diets, such as dairy, meats/alternatives, and fat groups were asked to be consumed in a free-living situation. To assess compliance of participants' intake of weight loss diets, participants were asked to record their 24-hour food intakes for 3 d/wk during weeks 2, 5, and 10 of the trial. Duration of all physical activities was collected, similar to dietary intakes. To obtain the metabolic equivalent for daily physical activity, the recorded physical activities were multiplied by the relevant metabolic equivalents task hours per day (MET-h/d) to give the MET-h/d values.