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About Diets
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      Metabolism is a biochemical process that combines nutrients with oxygen to release the energy your body requires in daily life.

Metabolism has two phases. The anabolic ("constructive") phase converts compounds from nutrients into substances the body can use. The catabolic ("destructive") phase reconverts these substances into more basic compounds that provide the energy release that keeps the body functioning.

Metabolism is measured in calories. How many calories you burn in a day depends on several factors, including:

- A person's basal metabolic rate (BMR)
- Level of physical activity
- The body's muscle to fat ratio

Many things can affect metabolic rate, including fevers, menstrual periods, digesting food and hormones such as insulin.

Basal Metabolic Rate

The basal metabolic rate (BMR) is a term used to describe how many calories the body burns 'at rest', simply to keep the brain and body functioning and heart beating. The BMR usually accounts for at least half of all calories burned during the day.

Most of your calories are 'burned' by muscle tissue. Fat is basically metabolic 'dead weight'. The more lean muscle mass you have in your body and the less body fat you have, the more calories the body tends to burn. This is the primary reason why anyone looking to loose weight should not only exercise frequently, but also include weight training as part of their exercise plan. As well, loosing muscle mass (which often happens when dieting) hampers the body's ability to loose fat.

The ability of lean muscle mass to cause an increase in the body's ability to burn fat is the reason why men, who generally have more muscle mass than women, tend to gain weight slower than women and loose weight faster than women.

Metabolism and Dieting

Experts agree that dieting, particularly "yo-yo" dieting, are generally counterproductive to long term weight loss. There are two main reasons for this. When the body is starved for calories, the body's fat storage enzymes learn to become more efficient. This is the result of evolution and our body's ability to withstand famine.

Training your body to store fat more efficiently is exactly what anyone looking to loose weight wants to avoid. As well, most dieters, particularly those who loose a large amount of weight in very little time, actually loose that weight in water and lean muscle mass loss. Frequently, diets suggest ingesting so few calories that the body doesn't get the energy it needs and the dieter ends up feeling sluggish and without energy to burn. The end result is a loss of lean muscle mass - the body's number one ally in the fight against fat.

The message is clear when considering metabolism and it's relation to weight loss. Do not starve your body. Instead, keep the energy flowing and burn it off in exercise, including exercise that builds lean body muscle.

Some interesting facts about metabolism

- as we age, our BMR decreases approximately 2% each decade
- about 10% of daily calories are burned during digestion
- over 50% of daily calories are burned by the body just to function
- 15-40% of calories are burned through physical activity (the amount depends on how much a person exercises)

The Mayo Clinic's Health Living Centers provides excellent advice and research about diet and nutrition. Excellent resources about diets and nutrition are offered by the website.

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