Brown Fat in Humans: Turning up the Heat on Obesity
- 1Dana-Farber Cancer Institute and the Department of Cell Biology, Harvard Medical School, Boston, Massachusetts;
- 2Division of Endocrinology, Diabetes & Metabolism, Department of Medicine, University of Pennsylvania, and the Institute for Diabetes, Obesity & Metabolism, Philadelphia, Pennsylvania.
- Corresponding author: Patrick Seale, , or Mitchell A. Lazar, .
The looming pandemic of obesity and overweight, driven by ready access to high-calorie food and an increasingly sedentary way of life, poses a severe threat to global public health. The pathological accumulation of excess dysfunctional adipose tissue that characterizes obesity is a major risk factor for many other diseases, including type 2 diabetes, cardiovascular disease, hypertension, stroke, arthritis, and various types of cancer (1). A basic, but often misunderstood, concept is that weight gain is caused by a fundamental energy imbalance, when energy intake from food chronically exceeds energy expended by physical activity and metabolic processes (Fig. 1). Humans have evolved efficient biological mechanisms to acquire and defend their energy stores. A therapy for weight loss must, therefore, involve a decrease in food intake and/or an increase in energy expenditure.
In addition to the better-known white adipose tissue that specializes in lipid storage and undergoes pathological expansion during obesity, mammals are also equipped with thermogenic brown adipose tissue (BAT). BAT evolved in mammals to dissipate large amounts …