Effects of inulin supplementation on body composition and metabolic outcomes in obese children


This was a randomized, double-blind, placebo-controlled trial conducted from August 2017 to July 2020 at King Chulalongkorn Memorial Hospital (KCMH), Thailand. The study was conducted in accordance with the Declaration of Helsinki and the Ethics Committee of Chulalongkorn University Medical School approved the study protocol (IRB No. 240/60). Participants signed informed consent forms prior to enrollment. This trial has been registered at http://www.clinicaltrials.gov under number NCT03968003. CONSORT was produced as a checklist of health research reports for randomized trials. Obese children aged 7-15 who had a BMI greater than the median plus 2 standard deviations (SD) from the WHO growth reference14 were recruited from KCMH’s Pediatric Nutrition and Pediatric Obesity clinics, as well as social media (Chula Kids Club). All the children who fulfilled the inclusion criteria as well as their parents were approached by the researchers and those who accepted the monthly follow-up and consented to the study were enrolled. Exclusion criteria were syndromic obesity, endocrine causes of obesity (e.g. hypothyroidism, growth hormone deficiency), concurrent use of drugs that influence appetite or body weight (e.g. example, corticosteroids) and participation in other concurrent weight reduction programs.

study design

The participants were randomly assigned to 3 groups: inulin, placebo and dietary fiber advice group. Randomization was performed using computer-generated permuted blocks of size 6. A research assistant who was not involved in the data collection and analysis generated the random allocation sequence and prepared the sealed envelopes. Other researchers recruited participants and blindly assigned them to each group. To ensure concealment, study products were weighed, packaged, and signed with consecutive numbers according to the randomization list by uninvolved personnel. The inulin group consumed 13 g of inulin powder extracted from Thai Jerusalem artichoke approximately 30 minutes before dinner daily. Participants were recommended to consume the powder by mixing the powder with 150ml of lukewarm water and then stirring the powder until dissolved. The placebo group consumed 11 g of isocaloric maltodextrin (Oligocarb; Ma-Jusmin Company Limited, Bangkok, Thailand) in the same way. Blinding of the placebo to match the light brown color of the inulin extract was addressed throughout the study. Both supplements came in identical foil pouches. All participants were followed monthly for 6 months. During the monthly visit, participants were asked to return all empty, half-empty and full sachets, and the information was recorded. Parents/guardians were asked to make a parental checklist and checked in with researchers during follow-up visits. The third group received structured advice (with pictures of portion sizes) to consume age-appropriate amounts of dietary fiber15.16. Research assistants conducted telephone contact every 1st and 3rd week to verify and monitor compliance and side effects.

Apart from the interventions, all groups received the same dietary advice regarding a diet low in energy (1000 to 1200 kcal/day) and low in fat (25% of total energy from fat). All participants were asked to exercise without weight bearing for 60 minutes a day at least 4-5 days a week, to maintain a physically active lifestyle and to reduce screen time.

Inulin Extraction Process

Inulin was prepared from Jerusalem artichoke (Helianthus tuberosus). Jerusalem artichoke dry energy was purchased from local distributors in Nakhon Ratchasima, Thailand. The product has been approved for human consumption by the Food and Drug Administration of Thailand (No. 30–1-14,358–1-001). The inulin extract was prepared according to the patented protocol developed by our team (Patent n° 15858, Inventor: Chonnikant Visuthranukul and Supakarn Chamni, Chulalongkorn University and National Science and Technology Development Agency, Thailand). Briefly, Jerusalem artichoke powder was decocted in water at 60-80°C for 45-90 min. The resulting slurry was filtered, mixed with absolute ethanol and incubated at room temperature overnight for inulin precipitation. Inulin was collected by filtration. All remaining moisture contents were dried at 40-50°C and pulverized to obtain the fine and homogeneous inulin powder. Inulin content was assessed based on standard methods for dietary fiber, including energy (ASTM Method D 240–76), total dietary fiber (AOAC (2016) 985.29), soluble dietary fiber (AOAC (2016) 991.42, 991.43), insoluble dietary fiber. fiber (AOAC (2016) 991.42), and fructans (Inulin + Oligofructose) (s) AOAC (2005) 997.08 + J. AOAC, 2000, 83(4); 1020–1025)17.18. The tests were carried out by a certified laboratory of the Institute of Nutrition, Mahidol University, Thailand. The degree of polymerization (DP) of the resulting inulin was determined by MALDI-TOF mass spectrometry and gel permeation chromatography coupled with multi-angle laser light scattering. Jerusalem artichoke inulin showing a large distribution of fructan polymerization containing a molecular mass of 3460 m/z, which refers to the large DP of the resulting inulin extract. Microbial and heavy metal contaminants, as well as pesticide residues were reviewed and confirmed by the Department of Science Service, Thailand. The inulin extract was kept in foil pouches and stored in a dry container at room temperature until use.

Assessment of food intake, physical activity and exercise

Food intake was assessed by a dietitian, using 3-day food records (two weekdays and one weekend day). Fiber and other nutrient intakes were calculated using the Institute of Nutrition, Mahidol University Calculation-Nutrients Version 3 (INMUCALs)19. Adherence to physical activity and exercise instructions was assessed by a physical activity questionnaire at each visit. Intensity of physical activity was defined by day/week and duration of physical activity in minutes/hours. Aerobic dancing or cycling with speed were classified as high intensity exercises. Brisk walking was classified as moderate intensity while walking from place to place for at least 10 minutes was classified as low intensity. Sedentary activity was defined as a lifestyle involving little or no physical activity that was questioned and assessed by a research assistant. Screen time, such as watching TV and playing computer, smartphone, and tablet games, was assessed separately from sedentary activity.

Anthropometry, body composition and clinical assessment

Trained personnel carried out the anthropometric measurement. Weight and height were measured without shoes and with light clothing using a stadiometer to the nearest 0.1 kg and 0.1 cm, respectively. Waist circumference was measured at the level of the navel after normal exhalation with the participants in a standing position. Hip circumference was measured at the maximum circumference of the hips. BMI was calculated as the weight in kilograms divided by the square of the height in meters (kg/m2), and the BMI z-score was calculated based on the 2007 WHO Growth Reference using the WHO Anthroplus program20. Body composition was measured by bioelectrical impedance analysis (BIA) using the InBody 770® (InBody Co., Ltd., Chungcheongnam-do, Korea). This multifrequency with 8-point tactile electrodes was evaluated in Korean children aged 6 to 18 years21 with a reproducibility of 99%. Fat mass index (FMI) and fat-free mass index (FFMI) were calculated in the same way as BMI22.

Blood pressure was measured by a tensiometer (Dinamap®). The presence of acanthosis nigricans has been documented by a pediatrician. Tanner’s staging was assessed by a self-administered photo questionnaire and verified by a pediatrician.

Metabolic profiles

Venous blood was drawn after a 12 h fast to assess biochemical parameters at the 1st and 6th study visits. Fasting blood glucose (FPG) was measured by the hexokinase method (GLUCOSE, Architech; Abbott Laboratories, Irving, TX). Serum total cholesterol, HDL-C and triglycerides were measured by enzymatic colorimetric assay (CHOLESTEROL, Architech; ULTRA HDL, Architech; and TRIGLYCERIDE, Architech; Abbott Laboratories). LDL-C was measured by a homogeneous liquid selective detergent (DIRECT LDL, Architech; Abbott Laboratories). Serum alanine aminotransferase (ALT) was determined according to the standard of the International Federation of Clinical Chemistry (ALANINE AMINOTRANSFERASE, Architech; Abbott Laboratories).

statistical analyzes

Sample size estimation: With a power of 0.80 and an alpha level of 0.05, the sample size of 55 obese children per group was estimated using one standard deviation of 0.267 and the minimum clinical difference for change in BMI z-score was 0.17.

Baseline characteristics of participants in each group were described as mean and SD or frequency and percentages. A one-way ANOVA was used to assess the difference in change in variable outcomes between baseline and Month 6. The Generalized Estimating Equation (GEE) model was used to assess changes in outcomes, which included body weight and adiposity, among three groups at three time points (baseline, three and six month). To assess the effect of time on the difference in outcomes between the three groups, the GEE model with an interaction term between the time point and the group was assessed using the likelihood ratio test. The alpha level of 0.05 was considered statistically significant for all analyses. All analyzes were performed using STATA version 16.1 (STATA statistical software: version 16. College Station, TX: STATA Corp LLC. 2019).