Obesity induces metabolic and functional alterations in skeletal muscle, particularly at the mitochondrial level, contributing to insulin resistance, oxidative stress, and reduced contractile capacity. This study evaluated the effects of moderate-intensity exercise, diazoxide, an activator of mitochondrial ATP-sensitive potassium (mitoK_ATP) channels, and their combination on mitochondrial bioenergetics in rats with high-fat diet-induced obesity over eight weeks. Eight experimental groups were used (n = 6 per group), with eight weeks of exercise and 14 days of diazoxide administration. Morphometric, biochemical, and functional parameters of mitochondria isolated from skeletal muscle were analyzed. Obesity was associated with significant increases in body weight, visceral adiposity, plasma glucose, and triglyceride levels, along with impaired mitochondrial respiration, increased mitochondrial swelling, reduced electron transport chain complex activity, increased oxidant-associated fluorescence, and decreased activity of superoxide dismutase (SOD) and glutathione peroxidase (GPx). In obese rats, exercise, diazoxide, and their combination were associated with favorable changes in redox-related parameters compared to the untreated obese group. Significant improvements were also observed in selected parameters of mitochondrial function, although responses varied among the interventions. Conversely, changes in certain morphometric and biochemical parameters, such as the Lee index and glucose levels, primarily reflected numerical trends toward control values. Overall, these findings suggest that exercise and diazoxide, individually or in combination, may attenuate selected mitochondrial alterations associated with obesity in this experimental animal model.