Effects of Diet-Induced Obesity and Programs for Body Weight Reduction on the Histostructure of the Triceps Surae Muscle in Male Rats

We studied the effects of visceral obesity induced by a high-calorie diet and health-improving variants of its correction on morphological characteristics of the muscle tissue in male Wistar rats. At stage I, the rats received standard (StD) or high-calorie diet (HCD) for 8 weeks. At stage II, the animals were divided into the following subgroups: no correction (StD and HCD), switching from HCD to StD (HCD/StD) and/or connection of physical activity in the form of treadmill running (StD+running, HCD+running, and HCD/StD+running) for the next 8 weeks. Diet-induced visceral obesity was shown to result in a decrease in the weight of the triceps surae muscle, fatty infiltration, intracellular edema, partial lysis of contractile elements, weak inflammatory response, and decreased muscle fiber area on cross section. Treadmill running (HCD+running) exacerbates the morphological changes, but returns muscle fiber area to normal. Correction of visceral obesity and relative normalization of muscle tissue structure was noted when switching to a standard diet (HCD/StD and HCD/StD+running).