When there are nutritional deficiencies, particularly in antioxidant vitamins such as B and C, metabolism can become less efficient.

Metabolism requires the smooth running of many complex physiological processes.

Some people simply have a naturally more efficient metabolism than others. The body typically starts to lose muscle after age 30, so everything else being equal - activity level, calorie intake - you'll gain weight because of this loss of muscle. Protein requires more energy to be broken down, digested, and absorbed, and resting metabolic rate typically goes up after eating protein as much as two to three times more than after eating carbohydrates and fats. However, if your caloric intake exceeds your body's ability to burn up those calories over time, the excess calories are converted into fat and glucose. One study found that as calorie intake increases, there is a corresponding increase in metabolic efficiency that is designed to maintain you around a particular body weight. At the same time, eating more food increases metabolism. In turn, the body is storing much of the limited amounts of food these individuals eat as fat and wasting muscle tissue as an adaptive mechanism to create an alternative energy source.

already running 25 percent to 60 percent below its ideal metabolic-efficiency level. I have found that most of the people who come to me with weight and health problems are usually already ingesting far fewer calories than they should in order to efficiently fuel their bodies. In his book Turn Up the Heat, Philip L. It will hold on to fat as protection. When you are eating an insufficient amount of calories, your body perceives itself to be in starvation mode and will start to cannibalize your own muscle, burning it off for fuel. Metabolism is affected by how much you eat. And some experts believe that aerobic exercise boosts your resting metabolism for several hours afterward, as your muscles burn calories to recover and repair themselves. Aerobic exercise, which increases heart rate, will also raise metabolism while you're exercising.

People who are overweight may have lost the assistance of brown fat, and their excess calories go into fat storage. The hypothalamus helps your nervous system trigger the action of brown fat, whose specialized mitochondria are particularly effective at generating heat and energy. It helps convert deposits of body fat into heat. According to Stephen Langer, an expert on weight loss and thyroid function, one lesser-known aspect of metabolism is brown fat, also known as brown adipose tissue (BAT). Goglia talks about the impact of a too-low-calorie diet on weight problems.