Basal metabolic rate, or BMR, is the bare minimum number of calories needed if you were to stay on the couch all day and do nothing. Your BMR decreases as you age. It also decreases in response to eating less food in an effort to lose weight. Your BMR naturally slows down later in the day.

Many medications have potential negative side effects. Depending on the type of medication, these can include changes in appetite, energy and activity level, metabolism and weight. Antidepressants are one class of medication that carries a risk of such changes.

You’re typically told to eat less and move more to lose weight. But if you eat too little, you'll face a metabolic slowdown that interferes with weight management. Eating enough calories at predictable intervals will help boost a metabolism that has stalled.

Neurotransmitters are the chemical communicators that are shared between neurons in your body, causing an action or reaction of a specific nerve or group of nerves. The neurotransmitters norepinephrine and serotonin play an important role in your psychological wellness.

If you struggle to lose every ounce -- and seem to gain it all back by simply looking at a cheeseburger -- you know the power of a slow metabolism. Your metabolic rate depends on a few factors within your control, such as your activity level, but factors outside your control can play a role, too.

Ah, the fresh air, the solitude, the relative quiet of early morning. If you are a morning person, there is nothing like getting a jump-start on the day by revving up your body's engine.

The body is comprised of several individual systems that work in conjunction with one another.

Progesterone helps form and thicken the endometrial lining in the uterus of pregnant women. Without progesterone, a fertilized egg will not attach to the uterine wall and placenta will not support an embryo. Women who experience multiple miscarriages may have low levels of progesterone.

Metabolism refers to the collective chemical processes that convert food into energy. Similar to gas for your car, food is your body's fuel. If you have a fast metabolism, your body lacks fuel efficiency.

The pineal gland, deep in the brain, is responsible for the production of melatonin, and adequate levels of melatonin are necessary for restful sleep. The body produces between 5 and 25 mcg of melatonin each night, according to the book "Melatonin."

Thyroxine is the main hormone produced by the thyroid gland and what controls the body’s basal metabolic rate (BMR). A person's basal metabolic rate refers to the minimum number of calories he needs to survive in the absence of any activity.

Your metabolism consists of the energy you use to exist, perform daily functions, exercise and digest food. Basal metabolic rate and resting metabolic rate are two different measures that tell you how many calories you burn without any extra daily activity -- as if you were lying in bed all day. You may see the terms "