Understanding the functional aspects of BAT under obese and overweight conditions is important to improve metabolic dysfunction. Mechanisms that regulate the quality of BAT are influenced by dietary lipids and plays a vital role in fat oxidation. Our imaging and molecular biology data suggests that lipid oxidative capacity of the mitochondria in iBAT is compromised with increased accumulation of lipids. High fat dietary feeding did not affect the mitochondrial content. However, the mitochondrial function was profoundly impaired. The novel finding in this study is the reduction in the activity of complex II in HFD fed rats leading to mitochondrial dysfunction.