Having a 'slow metabolism' can be a convenient excuse for those of us unable to watch what we eat or take enough exercise! But before we talk about the speeding up our 'slow' metabolism, let us understand what it is.
Metabolism is the process by which food is absorbed into the body to release energy. And our metabolic rate refers to how many kilocalories (energy) we burn in a minute, rather similar to the fuel consumption of a car. And like a car manufactured as a mini or large saloon, our working metabolism is defined mostly at birth through genetics, gender and body size, although it can be changed and adjusted through our dietary habits, fitness levels, coupled with our energy output.
Your Basal Metabolic Rate (BMR) is the amount of energy required to keep your body working normally (or ticking over, to use our car metaphor). Because even when our body is resting, calories are still being used for breathing, circulation, heartbeat, brain activity, etc. The BMR will also be influenced by our age, nutritional and physical status, as well as genetics.
Any physical exercise will raise the metabolic rate as your body begins to work harder, burning even more calories. In theory, the higher your BMR the more food you require to feed the energy, but if you are already eating too many calories then a higher BMR will burn the extra calories away. This is why regular exercise is an important part of any weight control programme, as you need to burn more calories than you take in to achieve weight loss.
Both the metabolism and metabolic rate can be changed. Crash diets, for example, can lower your metabolic rate to half the speed, while aerobic exercise can multiply it, leaving your metabolism raised many hours after exercising. By changing the kinds of food you eat, you can re-programme yourself to burn fat more efficiently.
An under-active thyroid gland is another 'often used' weight-gain excuse. The gland is situated in the lower front of the neck and produces hormones that help regulate the body's metabolism. If the thyroid is unable to produce sufficient hormones, then the body's organs can be affected, and weight gain can be just one of the symptoms. This condition is called 'hypothyroidism'. More typical symptoms include: intolerance of the cold; depression or lethargy; constipation; dry skin; thin or dry hair; poor memory and, of course, weight gain.
Diagnosis can be confirmed by taking a blood sample to measure the concentration of thyroid stimulating hormone, which plays an important role in regulating our metabolism. Permanently decreased metabolism can usually be treated successfully with drugs (thyroxine) and should then be checked regularly. About one person in fifty can be affected, usually more women than men.
The more muscle you have the more calories you burn, regardless of how active you are or how old you are. Metabolism does not slow down significantly due to ageing, but to lack of muscle, which can be the consequence of less physical activity. Muscle is live tissue and it's there working for you and burning calories all the time. For every extra pound of muscle you put on, your body uses around 50 extra calories a day.
People who go on a 'food-only' diet to reduce weight can actually lower their metabolic rate, rather than raise it. When food intake drops from a 'normal' intake the body recognises a lack of fuel and lowers the metabolic rate to conserve more energy. Another downside is that it also starts to store fat presuming that you may be going without food! A body that consumes 2500 calories a day, and burns 2500 calories a day will stay at the same weight. A body consuming 2500 calories daily but burning only 2000 will gain weight at the rate of about 1lb a week!
Eating little and regularly will keep your metabolism going faster than larger, less frequent meals. There are reasons why meal frequency may affect your metabolism as levels of thyroid hormones begin to drop within hours of eating a meal, and metabolism slows. Provided your small meals are healthy and don't degenerate into quick-fix, high fat, high sugar snacks, eating little and often can also help to control hunger and make you less likely to binge.