Supplementation with Conjugated Linoleic Acid for 24 Months Is Well Tolerated by and Reduces Body Fat Mass in Healthy, Overweight Humans

Abstract

After 12 mo in a randomized, double-blind, placebo-controlled trial of conjugated linoleic acid (CLA) supplementation (2 groups received CLA as part of a triglyceride or as the free fatty acid, and 1 group received olive oil as placebo), 134 of the 157 participants who concluded the study were included in an open study for another 12 mo. The goals of the extension study were to evaluate the safety [with clinical chemistry analyses and reported adverse events (AEs)] and assess the effects of CLA on body composition [body fat mass (BFM), lean body mass (LBM), bone mineral mass (BMM)], body weight, and BMI. All subjects were supplemented with 3.4g CLA/d in the triglyceride form. Circulating lipoprotein(a) and thrombocytes increased in all groups. There was no change in fasting blood glucose. Aspartate amino transferase, but not alanine amino transferase, increased significantly. Plasma total cholesterol and LDL cholesterol were reduced, whereas HDL cholesterol and triglycerides were unchanged. The AE rate decreased compared with the first 12 mo of the study. Body weight and BFM were reduced in the subjects administered the placebo during the initial 12 mo study (-1.6 +/- 3.2 and -1.7 +/- 2.8 kg, respectively). No fat or body weight changes occurred in the 2 groups given CLA during the initial 12 mo. LBM and BMM were not affected in any of the groups. Changes in body composition were not related to diet and/or training. In conclusion, this study shows that CLA supplementation for 24 mo in healthy, overweight adults was well tolerated. It confirms also that CLA decreases BFM in overweight humans, and may help maintain initial reductions in BFM and weight in the long term.

The role of conjugated linoleic acid in reducing body fat and preventing holiday weight gain

“…9-11 Gaullier et al 11 found fat mass losses of 2.4 and 1.7 kg during 1 year of supplementation with CLA in TG and free-fatty acid forms, respectively. In a 1-year, open-label extension of Gaullier's study 10 with all three groups taking CLA TG, there was a significant decrease in fat mass in the placebo-TG group (À1.7 kg), whereas the remaining two groups maintained their previous losses and showed additional, but non-significant, decreases in fat mass. During 12 weeks of supplementation, Blankson et al 9 showed that fat mass decreased by 1.2, 1.7 and 1.3 kg for CLA doses of 1.7, 3.4 and 6.8 g/day, respectively.…”

“…25 We did not see a change in liver function tests including AST, ALT, ALP and total bilirubin. Of six recent studies including similar measures of liver function, only Gaullier et al 10,11 showed significant within-group increases in AST. [8][9][10][11]13,29 However, this increase in AST was not significantly different from the control group and was not accompanied by changes in ALT or bilirubin.…”

“…6 Proposed mechanisms have included increased fat mobilization and oxidation, reduced adipocyte proliferation and differentiation, and increased apoptosis in pre-adipocytes. 6 Despite clear evidence that CLA reduces body fat in animals, the effect of CLA supplementation on body composition in humans has been inconsistent: of seven studies that have evaluated body composition change with mixed-isomer CLA among overweight or obese adults, [7][8][9][10][11][12][13] only three have shown a significant reduction in fat mass. [9][10][11] The conflicting results in human versus animal studies have been attributed to factors such as lower doses per unit body weight; the use of young, growing animals versus adult humans; and the limited sensitivity and accuracy of in vivo body composition measures.…”

“…6 Despite clear evidence that CLA reduces body fat in animals, the effect of CLA supplementation on body composition in humans has been inconsistent: of seven studies that have evaluated body composition change with mixed-isomer CLA among overweight or obese adults, [7][8][9][10][11][12][13] only three have shown a significant reduction in fat mass. [9][10][11] The conflicting results in human versus animal studies have been attributed to factors such as lower doses per unit body weight; the use of young, growing animals versus adult humans; and the limited sensitivity and accuracy of in vivo body composition measures. 6 In fact, a commonality among previous human studies has been the assessment of body composition with techniques, such as bioelectrical impedance analysis (BIA), dual-energy X-ray absorptiometry (DXA) and underwater weighing, that may be less sensitive in detecting change when compared to criterion multicompartment models.…”

“…28 The longest human trial of CLA to date reported no detectable change in glucose and insulin levels during 2 years of supplementation with 3.4 g/day mixedisomer CLA in the free fatty acid form; yet these individuals failed to show any improvements in glucose and insulin, which might have been expected for their weight loss, and there was a significant increase in insulin within the group taking CLA in the TG form. 10 We therefore cannot rule out the potential for small, subclinical effects to develop with prolonged use.…”