Lipedema is a painful fat disease of loose connective tissue usually misdiagnosed as lifestyle-induced obesity that affects ~10% of women of European descent as well as other populations. Lipedema is characterized by symmetric enlargement of the buttocks, hips, and legs due to increased loose connective tissue; arms are also affected in 80% of patients. Lipedema loose connective tissue is characterized by hypertrophic adipocytes, inflammatory cells, and dilated leaky blood and lymphatic vessels. Altered fluid flux through the tissue causes accumulation of fluid, protein, and other constituents in the interstitium resulting in recruitment of inflammatory cells, which in turn stimulates fibrosis and results in difficulty in weight loss. Inflammation and excess interstitial substance may also activate nerve fibers instigating the painful lipedema fat tissue. More research is needed to characterize lipedema loose connective tissue structure in depth, as well as the form and function of blood and lymphatic vessels. Understanding the pathophysiology of the disease will allow healthcare providers to diagnose the disease and develop treatments.