Devastating metabolic consequences of a life of plenty: focus on the dyslipidemia of overnutrition.

Although undernutrition and starvation continue to affect a substantial portion of the world's population, billions of people in both developed and developing countries are affected by the opposite problem: consumption of calories that exceed their daily energy expenditure, a condition of overnutrition. The body's response to a positive net energy balance is to store energy, predominantly as triglyceride molecules, in the subcutaneous and visceral fat compartments that expand and ultimately manifest in obesity. The body's fat depot, however, does not have an infinite capacity to store and expand, and at set points, which differ from individual to individual and are also influenced by ethnicity, energy substrates 'spill over', resulting in 'ectopic' fat storage in tissues and organs that are not typically major fat storage depots in lean individuals. A complex web of nutrient overload, chronic inflammation, hormonal action, mitochondrial dysfunction and insulin resistance, to mention some of the factors involved, results in devastating metabolic abnormalities that have far reaching implications for health and disease, leading ultimately to some of the most common chronic diseases of our time; i.e., diabetes mellitus, cancer, chronic liver disease and atherosclerosis. Given the complexity and wide-ranging manifestations of overnutrition (also referred to here as insulin resistant states), we will highlight a specific aspect of the condition, that of dyslipidemia. This review will draw mainly on knowledge acquired from whole body, integrative physiology research in animals and humans affected by overnutrition, and will demonstrate how these types of studies can shed light on our understanding of the pathophysiology of the typical dyslipidemia of obesity, insulin resistance and type 2 diabetes.