December 13, 2005
The Effects of CLA Supplementation on body composition, exercise endurance, and serum insulin levels.
More and more in the literature the benefits of CLA and EFA supplementation is being realized. At a time when obesity rates are at an all-time high and which is correlated with insulin resistance and diabetes, the stage has been set for may discoveries in lipid-research, with lipids being so intimately involved in with obesity and the metabolic syndrome whether referring to body fat stores or lipids in the diet. CLA has shown much promise in the area of obesity and insulin resistance, however the exact mechanisms by which it elicits its positive effects are incompletely understood. The abstract below is from a study that examined the effects of a typical dose of CLA supplementation on exercise endurance and body composition, while also analyzing its effect of factors involved in dyslipidemias and insulin resistance.
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Summary of Results and Practical Applications
In this study 44 healthy female subjects were evaluated for the effects of CLA supplementation on Body Composition and endurance exercise performance. Subjects consisted of CLA, CLA+ 30 min cardio 3days/week, exercise only, and a control group; no exercise and no CLA. The subjects were evaluated after 6 weeks. The CLA, Exercise+ CLA, and Exercise-only groups all showed favorable changes in body composition. The results of the study were that the CLA and CLA+ Exercise group showed in increase in fat free mass in addition to a decrease in bodyweight compared to exercise-alone and the control group. The study failed to show any significant changes in serum leptin, apo-AI, apo-B, total cholesterol, HDL, LDL, free fatty acid, and triglyceride levels. In addition, subjects in the CLA and CLA+exercise group failed to show increased endurance compared to the exercise-only control. Serum insulin and glucose concentrations, however, were reduced in both the CLA and CLA + exercise groups.
The fact that this study showed improvements in body-composition in addition to decreases in serum insulin and glucose is extremely important, suggesting that CLA supplementation is directly influencing insulin sensitivity, likely at the muscle insulin-receptor level. It has been known for quite some time that high serum triglyceride and free fatty acid concentrations are correlated with insulin resistance. CLA failed to affect these in addition to markers of cholesterol metabolism, including apo-AI, apo-B, total cholesterol, HDL, LDL, further supporting an insulin-sensitizing mechanism resulting in an improvement in body composition. Leptin, along with another hormone, resistin, is secreted by fat cells in addition to free fatty acids and further contributes to insulin resistance; although resistin was not measured, leptin levels were additionally shown not to change. .It is becoming more- and more recognized that the body fat mass is an endocrine organ in-and of itself; the more fat we get the more insulin-resistant we become and the fatter we get; truly a viscous cycle. It should be noted that there are also insulin receptors in adipose tissue; however when insulin receptors of fat cells are stimulated glucose is taken into the fat cell, converted to triglyceride, and stored as body fat. While in advanced cases of diabetes it is advantageous to augment the sensitivity of insulin receptors on fat cells as well as muscle cells in order to reduce a dangerously high serum glucose level, in non-diabetic subjects it is desirable for muscle cell insulin receptors to be much more sensitive relative to those on fat cells in order to store the least possible amount of body fat. While the regulatory system that determines the fate of glucose uptake into muscle or fat cells is extremely complex and incompletely understood, it is obvious that energy intake is a dominant factor in muscle-vs.-fat cell insulin sensitivity. The results of the study are exciting because they suggest that CLA preferentially increases insulin sensitivity of insulin receptors on the muscle cell independent of the energy balance, explaining the positive changes in body composition, even in the absence of aerobic exercise in the CLA-only group. While there is certainly much more to this story this study provides convincing evidence of the benefits of CLA supplementation for any fitness program. The supplementation of CLA will help to increase muscle mass and decrease body fat in conjunction with a diet and exercise program.