Are Your Muscle Fibers Making You Fat? by Jerry Brainum 5/25

 

 

 

We've all seen people who seem able to eat and drink anything they want with impunity. They seem to be immune to becoming obese. What are the factors that explain this? Some people remain thinner, regardless of how much food they consume, because they have a faster metabolism. The resting metabolic rate is controlled by thyroid hormone output and muscle mass. The notion of "faster metabolism" is largely nonsense, as the resting metabolic rate among individuals does not differ significantly to explain the apparent differences in body composition. Another often-repeated statement is that people tend to gain body fat as they age because their resting metabolic rate declines. However, recent studies show that, contrary to popular belief, the resting metabolic rate (RMR) does not decline with age. On the other hand, losing muscle mass due to a long-standing lack of muscle stimulation through physical activity and exercise can slightly lower the RMR with age. Those who maintain a more svelte appearance do not produce greater amounts of thyroid hormone. In many cases, they have hypothyroidism or low thyroid hormone output. 

If none of the usual explanations of why some people don't get fat are true, how is it explained? Several explanations are offered to explain this. One is that they engage in what's known as non-shivering thermogenesis. This involves constant small movements, such as fidgeting, that can burn a surprising amount of calories. Another feasible reason to explain why some people don't gain body fat is related to a specialized type of body fat called brown adipose tissue, or BAT. BAT is brown because it contains an abundance of blood vessels as well as mitochondria. The mitochondria are the powerhouse of cells, where energy is produced as ATP  and fat is oxidized. More active mitochondria equal a greater ability to oxidize or "burn" stored fat. BAT is a thermogenic tissue that converts calories, including excessive calories, into heat. As such, those calories are not stored as body fat. Previously, scientists thought BAT only existed in infants, where it was needed to keep the body warm. More recently, BAT was shown to also exist in adults, and since BAT is like having an internal heater, it burns up excess calories and prevents fat gain.

Indeed, some scientists who study BAT think it may be a possible cure for obesity. They say this because BAT can be manipulated by exercise and diet. Certain food supplements promote the conversion of white adipose tissue, the usual kind of stored fat, into BAT. What these specific supplements are will be discussed in an upcoming article in Applied Metabolics. Training in a cold environment is another way to promote BAT. Note that a primary function of BAT is to warm the body . . .