The present study found that microencapsulated CLA supplementation significantly reduced plasma insulin concentrations. This change was also observed in the placebo group, although it was not statistically significant. This may be attributable to changes in body composition in both groups. Furthermore, microencapsulated CLA supplementation was associated with decreases in glycemia and insulin resistance, but these were not statistically significant. This could be due to the fact that subjects participating in the study were nondiabetic and the study variables may not be as sensitive to changes in extreme ranges.29
Moreover, the microencapsulated formulation of CLA enabled oxidative stability that could improve the study variables more than studies that have used the purified form of CLA. Other studies have shown either no interference30
or harmful effects on glucose metabolism.32
Some studies have found higher glycemia and insulin resistance with use of CLA,12
and the change is more significant in studies using the trans
The lipid profile did not change significantly with microencapsulated CLA supplementation in this study. These findings are similar to results from other studies.35
Moreover, the effects of CLA on the lipid profile are controversial due to the difference in dosages of CLA used, proportions of CLA isomers, and population samples. Some studies showed an increase34
and others a reduction in high-density lipoprotein cholesterol,12
and a reduction in total cholesterol, low-density lipoprotein cholesterol,11
with CLA supplementation.
There was no significant change in blood pressure with microencapsulated CLA supplementation. Raff et al41
and Sluijs et al42
evaluated the effects of CLA supplementation with an equivalent amount of isomer mixtures in individuals with normal weight and in obese subjects, respectively, and detected no change in blood pressure levels. On the other hand, some studies have found a significant decrease in blood pressure in groups on CLA supplementation.37
In this study, both treatment groups showed a decrease in body fat mass, with no significant differences between groups. However, these results were observed at an earlier time in the microencapsulated CLA group, with significant changes after 30 days in contrast with the placebo group, in which the changes occurred only after 90 days. It is important to consider that early reduction of body fat provides people with encouragement to continue on a hypocaloric diet and develop healthy lifestyle habits.
The current study confirmed previous observations indicating body fat mass reduction with CLA supplementation.44
Gaullier et al11
observed a decrease in body fat mass by supplementation with an isomeric mixture of CLA at doses of 3.4 g/day in subjects without dietary restriction for 24 months, with a significant reduction in body fat mass only in the first 6 months. After this period, the placebo group showed the same results, suggesting an adaptation mechanism or a decrease in the effectiveness of CLA supplementation. However, the positive results seen with the supplemental CLA mixture were observed only after 3 months. On the other hand, some studies did not show a reduction in body fat mass.29
Among the mechanisms by which CLA decreases body fat, there is one that may be validated, ie, CLA prevents lipid accumulation in human adipocytes by acting as a modulator of peroxisome proliferator-activated receptor gamma.47
In the present study, waist circumference did not show any significant change between groups, but decreased significantly in the placebo group from day 30, even though both groups achieved a reduction in body fat mass. These findings are in accordance with those of other studies reporting that CLA supplementation promotes reduction of body fat mass, mostly in areas other than the abdomen, despite that fact that CLA has a tendency to decrease the amount of abdominal fat mass.13
In this way, women with a gynoid fat distribution will probably benefit from use of CLA. Although microencapsulated CLA reduced body fat mass in our study, it did not cause a significant reduction in body weight. This result is similar to that found in other studies.30
Subjects from both groups showed remission of components of the metabolic syndrome, underscoring the importance of a hypocaloric diet in the treatment of this condition.49
The effects of CLA supplementation on blood pressure and biochemical variables suggest that microencapsulated CLA supplementation in women with metabolic syndrome for 3 months is safe. Only female subjects were chosen for this study due to gender-related differences in body composition.25
Because we evaluated body composition as an outcome variable, we aimed to homogenize the study sample. Moreover, Chen et al39
showed a better effect of CLA supplementation in lowering body mass index in female subjects than in male subjects.
The limitation of this study is that the sample size was small due to the strict inclusion and exclusion criteria. On the other hand, this is the only study that has evaluated the effects of microencapsulated CLA in women with metabolic syndrome.