Effect of omega-3 fatty acids supplementation on anthropometric indices in children and adolescents: A systematic review and meta-analysis of randomized controlled trials
Introduction
Childhood obesity is a major public health problem with a global prevalence greater than 23 %.1,2 There has been a steady increase from 5 million to 50 million in girls and from 6 million to 74 million in boys from 1975 to 2016.3 Obesity in childhood has been associated with negative consequences for youth physical and psychosocial health.4, 5, 6 Moreover, childhood obesity is associated with an increased risk of morbidity and early death from cardiovascular diseases, diabetes mellitus and cancer,2,7,8 demonstrating the global importance of prevention and treatment of children and adolescents' obesity.
Lifestyle modifications including diet, behavior and physical activity alterations, anti-obesity medications and bariatric surgery are the main strategies for obesity management. In spite of the various treatments options, dietary factors are the main interventions to treat excess body weight.9 One dietary component that has the potential for obesity control is omega-3 polyunsaturated fatty acids (omega-3 FAs). In vitro and in vivo studies have confirmed that omega-3 FAs are an essential nutrient for humans, have many biological effects and may play an important role in health by improving triglyceride levels, affecting vasodilation, anti-inflammatory properties and reducing fat mass.10, 11, 12, 13 Omega-3 FAs have a body weight/fat mass reducing effect in high fat diet-fed obese animal models.14,15 Increased adipocyte apoptosis and fat oxidation, attenuated appetite, elevated plasma adiponectin, altered energy expenditure and gene expression may account for some of the mechanisms of action involved in the beneficial effects of omega-3 FAs on body fat.16, 17, 18 It remains unknown whether omega-3 FAs supplementation has anti-obesity properties for children and adolescents, though there is emerging evidence that omega-3 FAs may improve lipid profiles11,19, 20, 21 and cardiovascular function22, 23, 24, 25 in child and adolescent trials.
The results from randomized controlled trials of weight reduction effects of omega-3 FAs in overweight/obese children and adolescents has not reached a consensus, partly due to the limited number of subjects in these studies, varied intervention methods, the source, amount and duration of omega-3 supplementation, and race, age, sex, and initial weight of subjects. Omega-3 FA has high eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) content. Several studies have reported that omega-3 FAs have a beneficial impact on anthropometric measurements in children and adolescents, and patients with and without metabolic disorders. Some of these studies have shown that omega-3 FAs has lowering effect on weight,23,24 BMI24,26 and waist circumference23,24; however, other studies have shown increasing effects on weight 27 and waist circumference.28 Still other studies did not report any impact on weight28,29 or BMI.27, 28, 29 A recent meta-analyses that looked at omega 3-FA intake in adults found that supplementation modulated central obesity with no observed effect on body weight.16,30,31 Furthermore, the impact of maternal omega-3 FAs supplementation during pregnancy on the body weight of children has demonstrated conflicting results.32, 33, 34, 35, 36 No systematic review or meta-analysis has examined the impact of omega-3 FAs on anthropometric indices in children and adolescents. Therefore, we have conducted the first meta-analysis examining the role of omega-3 FAs supplementation on anthropometric indices in children and adolescents.
Section snippets
Search strategy
We performed a extensive online database search of the published literature on omega-3 FAs supplementation and anthropometric indices in children. We used SCOPUS (http://www.scopus.com), Web of Science (http://apps.webofknowledge.com), PubMed (http://www.ncbi.nlm.nih.gov/pubmed), EMBASE (http://www.embase.com), and the Cochrane library (http://www.thecochranelibrary.com) databases from the index date through April 2019 with the keywords: Childhood Obesity OR Adolescent Overweight AND Fish Oil
Search results
In total, our search yielded 3681 articles initially through the database searches. Of these, 1316 studies were duplicates and 2330 studies were excluded because they were irrelevant to the current meta-analysis based on titles and abstracts screening. Of the 35 potentially relevant studies identified, six23,24,26, 27, 28, 29 met the inclusion criteria of our meta-analysis. We excluded 29 studies due to: 22 having no relevant variables or sufficient data and authors did not reply to our email;
Discussion
This meta-analysis of six randomized, placebo-controlled trials, determined whether omega-3 FAs supplementation could have an effect on anthropometric indices with the use of a random effects model. To our knowledge, this is the first systematic review and meta-analysis that has evaluated the effect of omega-3 FAs supplementation on anthropometric indices in children and adolescents. In our study, we showed that omega-3 FAs intake by supplementation did not lead to anthropometric changes in the
Authors' contributions
SH.J. contributed to study design and preparing the final article version. J.H. contributed to performing search, data collection, data analysis, and interpretation, and drafted the manuscript. Z.M. contributed to interpretation, drafted and edited the manuscript. M.S. (Mehdi Sepidarkish) contributed to performing search and statistical analysis. GH.N. contributed to interpretation and edited the manuscript. M.S. (Marsa Zaroudi) contributed to study design, performing search, data collection,
Declarations of competing interest
None.
Acknowledgments
We thank Iran University of Medical Sciences (IUMS) for providing research atmosphere. The authors thank Professor Wendy H. Oddy from Menzies Institute for Medical Research at the University of Tasmania, for helpful contributions in the writing of this manuscript. We also thank Malihe Khoramdad for useful suggestions regarding writing of the manuscript. I received acknowledgement permission from Dr. Wendy H. Oddy from Menzies Institute for Medical Research at the University of Tasmania and from
Funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
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