What is brown adipose tissue?
First, let us delve into answering what adipose tissue is, and then we can assimilate the differences between the types of adipose tissues. The adipose organ must send a signal to the brain to regulate the need for food. If these signals are not accurate, it will cause the individual to have unnecessary cravings for food. These cravings cause the individual to intake more energy or calories than they are expending. The excess calories are stored in the adipose organ. When the adipose organ is filled, hyperplasia will occur, and the individual is now left with more adipose organs. The new organs exhibit the same inaccurate signals to the brain, which in turn will cause more cravings, so the cycle continues. This is thought to be one of the causes of obesity. The enzyme lipoprotein lipase resides in the fat cell and accumulates the fatty acids from the blood and other sources. The cells also have another enzyme called hormone sensitive lipase, which is responsible for the breakdown and release of triglycerides from the adipose organ. Fat cells, which contain more hormone sensitive lipoprotein lipase, will have a better chance of breaking down the triglycerides than the cells with less active lipoprotein lipase. This will lead to less hyperplasia and will slow down the fat accumulation leading towards obesity.
We can now get to the original question. Brown adipose tissue is more vascular and is heavily packed with mithochondria. Brown adipose tissue is used in thermogenisis or heating of the body. It is generally much less active than its white tissue counterpart. White adipose tissue is used as a substrate in the production of energy or ATP. Brown tissue cannot be used as substrate and is not involved in the ATP process. Brown adipose tissue releases energy straight into the body in the form of heat. We must accept, at least for now, that many of the controlling mechanisms of fat cells and their role in hyperplasia are not fully understood. The scientific community is hard at work trying to figure out exactly how it works so we can fight against one of the largest health concerns facing Americans: obesity and its secondary complications of diabetes and heart problems.
I hope this answered your question without leading you in a different direction. For the personal trainer, the incongruence between white and brown adipose tissues will rarely make a significant difference. In a nutshell, we can only process white adipose tissue for energy production or aerobic production of ATP. Brown adipose tissue can produce energy independently of ATP for the sole purpose of heat production.