Improvement of the lipid profile with exercise in obese children: A systematic review

Abstract

Objective

The objective of this systematic review was to assess the effectiveness of different physical exercise interventions on the lipid profile (high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), total cholesterol (TC), and triglycerides (TG)) of obese children.

Method

A computerized search was made of seven databases using keywords. Effect sizes (ES) and 95% confidence intervals were calculated, and the heterogeneity (I²) of the studies was estimated using Cochran's Q-statistic applied to the effect size means. The studies were grouped according to the intervention program—aerobic alone or combined (aerobic fitness, strength, and flexibility).

Results

Seven studies were selected for review as satisfying the inclusion criteria. Six were randomized controlled trials (n = 318) and one was a controlled clinical trial (groups not randomly assigned) (n = 38). The main cumulative evidence indicates that the programs based on aerobic exercise alone have a moderate (ES = − 0.49; I² = 87) and a large effect (ES = − 0.55; I² = 77) on LDL-C and TG concentrations, respectively; and the programs based on combined exercise have a moderate effect (ES = 0.50; I² = 0) on HDL-C concentration.

Conclusions

The programs based on aerobic exercise (60 min, 3 times/week, ≤ 75% maximum heart rate) improve the LDL-C and TG concentrations. Moreover, the programs based on combined exercise (≥ 60 min, > 75% maximum heart rate) also improve the HDL-C concentration.

Introduction

The lipid profile is defined as the relationship between the blood concentrations of total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and triglycerides (TG) (Grundy et al., 2005). Dyslipidemia is an alteration of the profile corresponding to abnormal blood levels of TG and/or cholesterol-carrying lipoproteins affecting one or all of the subfractions of blood lipids. Characteristically, these levels are abnormally high, although some forms of dyslipidemia may include low values (typically of HDL-C) (American College of Sport Medicine, 2010). Dyslipidemia is associated with cardiovascular disease (Rohatgi, 2010). Prospective studies show that the serum lipid and lipoprotein levels can track from childhood into young adulthood and are predictive of adult levels (Lobstein et al., 2004). Much of the information on atherosclerosis in children comes from studies on autopsies after accidents. The Bogalusa Heart Study concluded that 50% of children of 2–15 years had evidence of fatty streaks in the arterial intimae (Berenson et al., 1998). The American Heart Association therefore stresses the need to develop strategies for primary prevention of atherosclerotic cardiovascular disease in childhood (Kavey et al., 2003).

In this sense, obesity in childhood causes a wide range of co-morbidities including dyslipidemia among others (Burke, 2006). Worldwide, the prevalence of childhood obesity has increased greatly during the past three decades (Han et al., 2010). In the young, obesity accelerates the advance of atherosclerosis even before clinical symptoms appear (McGill et al., 2002). For instance, according to the latest report of the American Academy of Paediatrics, it increases the risk of future coronary artery disease, although the actual risk is unknown (Daniels and Greer, 2008). Children who are obese or overweight with co-morbidities (dyslipidemia, atheroma, or hypertension) should receive treatment (Han et al., 2010). Frequently, an exercise program is used to treat obese children because it improves aerobic fitness (Saavedra et al., 2011), although this improvement is less clear than for normal-weight children (Watts et al., 2005). It also has to be borne in mind that the maturing process in children causes their physiological response to exercise to be different from that of adults (American College of Sport Medicine, 2010). For children, the treatment of obesity and its associated pathologies ultimately involves the child eating less and being more physically active. Increased physical activity has been associated with increased life expectancy and decreased risk of cardiovascular disease (Williams et al., 2002). One study in normal-weight children have reported little or no alteration of the lipid profile following programs of physical exercise (Stoedefalke, 2007). The overall findings of a recent meta-analysis of aerobic exercise and lipid profiles in children and adolescents which considered only studies carried out in the United States suggest that short-term aerobic exercise does not improve HDL-C, LDL-C, or TC, but does reduce TG (Kelley and Kelley, 2007). It has to be noted, however, that this meta-analysis included only two studies which clearly reported that all the subjects studied were overweight or obese. There is little information available on how obese children who are prone to lipid profile alterations respond to exercise. One review on overweight and obese children suggests that diet is more relevant than exercise in improving the lipid profile, although more information is required since physical exercise does indeed lead to improvements in blood pressure and body composition (Watts et al., 2005). Given this context, the purpose of this systematic review was to examine the evidence for the effectiveness of diverse exercise interventions on the lipid profile (HDL-C, LDL-C, TC, and TG) of obese children.