Your metabolism is the rate your body uses energy -- not just for movement, but for countless chemical or "hidden" processes, such as cell growth, hormone adjustment and blood circulation. Your metabolism is influenced by many factors, including age, gender, diet and activity level. It's normal for your metabolism to slow down as you age -- about 3 percent for every decade, but you can also permanently slow your metabolism by changing your body composition or consuming too few calories -- putting your body into "starvation" mode.
Basal Metabolic Rate
There are three components to your metabolism. The majority of your energy is used for your Basal Metabolic Rate, keeping your body alive. Physical activity accounts for up to 20 percent of your energy and digestion uses between 5 and 10 percent. You can slow your BMR by changing your muscle-to-fat ratio. Muscle uses more energy, even at rest; the higher your muscle-to-fat ratio, the faster your metabolism. You can permanently slow your metabolism by losing muscle mass and gaining gaining body fat. Following a low-calorie, low-protein diet or discontinuing your strength-training exercises will slow your metabolism.
Calories and Metabolism
Your metabolism has a built-in survival mechanism for times of famine of long periods of fasting. When you don't eat enough calories to support your BMR, your metabolism slows down and conserves energy. This slowdown is why dieters often hit a plateau or their weight-loss efforts stall. The National Institutes of Health say you need a minimum of between 1,200 and 1,500 calories daily to keep your metabolism functioning normally. You can slow your metabolism by eating fewer than 1,200 calories every day. In general, men need more calories than women and younger people need more calories than older ones.
Dietary Choices
Certain foods speed up your metabolism; if you eliminate these foods, your metabolism will slow down. According to Dr. Mark Hyman, author of "Ultra Prevention" a high-fiber diet can boost metabolism by up to 30 percent. If you eat less than 25 g of fiber daily, your metabolism suffers. Also, caffeine speeds your metabolism; just 1 cup of coffee can boost your metabolism by 12 percent -- burning about 100 extra calories. Go caffeine-free to slow your metabolism.
Eating
What you eat and when will impact metabolic function. When you go for long periods of time between meals, your metabolism starts to slow down. Your body doesn't know when it will have a fresh supply of calories, so it goes into "mini-starvation" mode when you wait more than four or five hours between meals. Fat and carbs digest relatively easily and don't require a great deal of energy to process -- only between 4 and 6 percent; but protein may use up to 30 percent of the energy it provides simply to be digested. The lower your protein consumption, the lower your metabolism.
References
- MayoClinic.com: Metabolism and Weight Loss: How You Burn Calories; October 2009
- Medline Plus: Tips for Losing Weight; David Zieve, MD,; October 2009
- Better Health Channel: Metabolism Explained
- Ultra Prevention: Top 10 List for Successful Weight Loss
- Nutritional Reviews: Caffeine Effects on Weight Loss and Sport
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