Metabolism, Weight Loss and How to Boost Both

Fast metabolism, slow metabolism, phfft...what's the difference?

Actually, it's a pretty big one, as it turns out. Possibly big enough to stop you from losing weight. Ah! Now you're interested...

Metabolism is a much-talked-about, little-understood topic among people who are trying to gain control of their weight. To find out what you need to know about the big difference your metabolism can make, and what you can do to change it, read on.

What's your Basal Metabolic Rate?

The standard measurement for metabolism is called the Basal Metabolic Rate (BMR). This describes the minimum amount of calories needed to simply keep your body going, sustaining vital functions such as digestion, breathing and heartbeat.

BMR varies a lot between different individuals. These variations can make the difference between someone being overweight or of normal weight. For example, many obese people don’t eat any more food, and might eat less than non-obese people. For many obese people, this is the result of an extremely low level of physical activity. For others, it may simply mean that the obese person has a more efficient metabolism that requires fewer calories.

BMR generally accounts for around 1200-1400 calories per day in females, and 1400-1800 calories in males. This is the number of calories it takes for you to stay alive. Many factors affect BMR including:

  • Gender: Men tend to have more lean muscle in their bodies than women. Lean muscle requires more calories, so men’s BMR is greater than women’s.
  • Age: Because of the increased activity of cells undergoing division, the younger the person, the faster their metabolism. There is therefore a decline in BMR of approximately 2% for every 10 years after age 30.
  • Weight: The heavier a person is, the higher their energy requirements, so they need more calories to keep their body functioning and moving. Their BMR is higher, but that doesn’t mean their metabolism is faster; a point of confusion sometimes!
  • Height: The taller a person is, the higher their BMR as they have more body surface area (skin) exposed to the outer elements, equating to greater heat loss.
  • Environmental temperature: People living in tropical or very cold climates tend to have BMR's 5 - 20% higher than those living in moderate climates.
  • Physical activity: People who are physcially active generally have a higher BMR than those who are not.

Increasing your metabolism

The higher your metabolism, the faster you will burn calories. So the obvious question is - how do you increase your metabolism? Exercise can make a big difference for several reasons.

First, it can increase the muscle component of your Lean Body Mass (LBM). Your LBM is made up of your muscles, bones, organs such as the liver and heart, and the fat stored in your heart, lungs, kidneys, intestines, muscles, nervous system and bone marrow.

The greater the muscle component of your LBM, the higher your metabolic rate, i.e. more calories are burned. Males usually have a higher LBM (and therefore a higher metabolic rate) than females by virtue of their larger muscles. Some female athletes, however, such as swimmers and shot putters, may have a higher LBM than a male of equal weight.

You don't need to become muscle-bound to significantly raise your metabolic rate. Any exercise will tone and improve your muscle build and, as a result, burn extra calories and help use fat stores.

Second, exercise has the added advantage of increasing metabolic rate for up to 24 hours after you've finished working out, depending on how strenuous the exercise was. So when you relax in a chair after a brisk walk you are burning up more calories than the person sitting beside you who didn't exercise.

Without exercise your metabolism slows down. When you try to lose weight just by cutting calories, you actually lose muscle from your LBM as well as body fat. This has the effect of slowing down your metabolism. But if you exercise as well, then mainly body fat is lost while LBM is maintained or, more likely, increased. For this reason, exercise makes weight control easier.

Crash diets slow your metabolism down

The advertising claims for some diets can be quite dramatic. Claims of an 8 kg loss in two weeks are common. What is not told, is that about 6 kg of that weight loss is fluid and muscle tissue. The overall effect is to dehydrate the body and reduce muscle tissue, the very tissue that needs to be maintained and built up. Soon the body takes steps to regain the lost water and weight begins to rise, causing frustration and disappointment.

The rapid loss in weight is seen by the body as a “famine” situation. In a concerted effort to survive, the body dramatically reduces its metabolic rate within 24-48 hours after you start dieting. The reduction in basal metabolic rate can be as high as 45%. This is exactly the opposite effect to what you want for long-term weight control.

Repeated bouts of severe calorie restriction can actually have a drastic long-term effect on weight loss. The body adapts to these constant periods of “cyclic fasting” by slowing down metabolic rate to conserve energy. The result is that diets become progressively less effective.

Menstrual cycle boosts metabolism! (But not by much)

In the two weeks before menstruation begins (i.e. after ovulation) there appears to be a natural inclination for women to increase their food consumption. Biologically, this makes good sense as the body is preparing for a possible pregnancy. One study estimated the increased food intake to account for an extra 500 calories a day for the 10 days before menstruation. Chocolate especially seemed to be craved for at this time - a potential contributor to weight gain.

Within this same two weeks, basal metabolic rate increases by about 10%. However, this increase does not compensate for the extra 500 calories consumed on average! Some control over food intake is required to prevent weight gain. Women on the pill may not experience this effect of increased basal metabolic rate.

Smoking and metabolism

When someone quits smoking, weight is often gained even if they don’t alter their diet or their exercise routines at all. That’s because smoking causes the body to burn slightly more calories in order to cope with carbon monoxide and other tobacco toxins. When someone quits, their metabolism slows down to more normal levels, which means fewer calories are burned. This can lower energy needs by as many as 200-500 calories.

This might sound like a good reason to continue or take up smoking. Not so! It is far healthier to be overweight than to be a smoker. Weight gains when you quit smoking can be avoided by sensible eating and daily exercise. Exercise in particular can be very effective in countering the drop in metabolic rate.

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