Hormonal, metabolic, and skeletal muscle adaptations following weight loss: Effect of dietary fat type

These studies investigated the effect of dietary weight-loss and a specific dietary fat type, ALA(18:3n-3), on the hormones leptin and insulin and the peroxisome proliferator activated receptor (PPAR) family of nuclear receptors in the skeletal muscle of obese humans. All subjects were prescribed hypocaloric diets at 80% of resting metabolic rate until 10% weight-loss was achieved. In addition, a subset of subjects exchanged some of their dietary fat with a flaxseed oil capsule supplement because flaxseed oil contains ∼60% ALA(18:3n-3). The difference in fatty acid diet composition between diets was reflected in erythrocyte membranes, as flaxseed oil supplemented subjects experienced a significant increase of ALA(18:3n-3) composition in the erythrocyte membranes. Western blots of PPAR isoforms showed that PPARβ significantly increased with dietary weight-loss. The effect of weight-loss was reversed, however, in subjects supplemented with ALA(18:3n-3). A similar, but insignificant effect was seen for PPARα, and the opposite effect was seen for PPARγ. Plasma concentrations of leptin and insulin decreased significantly for both groups, but there was no effect of ALA(18:3n-3) supplementation. The observations seen in these studies may be important in future treatment of obesity. The significance and relationship of these observations is discussed, in addition to ideas for future research.