Metabolism, Weight Loss and How to Boost Both

Metabolism… everyone wants a faster one, but not many people truly understand what this means.

Surprisingly, the difference between a fast metabolism and a slow one could be the difference between whether you can shed those extra kilos or not! While it’s a widely discussed topic, capitalised upon by endless weight loss products claiming to be able to boost your metabolism, do you know how you can change your metabolism yourself?

What’s your Basal Metabolic Rate?

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

BMR varies significantly between different individuals. These variations can mean the difference between someone being overweight or of normal weight. For example, many obese people don’t eat any more food, and might even eat less than non-obese people, yet they gain and store weight owing to the fact they have a far lower BMR. For many overweight people, this is the result of an extremely low level of physical activity, and for others it simply means their BMR 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 (if you’re living a sedentary lifestyle). 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 often higher than women’s.
  • Age.  Because of the increased activity of cells undergoing division, the younger you are, the faster your metabolism. BMR declines by approximately 2% every 10 years after age 30.
  • Weight. The heavier you are, the higher your energy requirements, so they need more calories to keep your body functioning and moving. However, a higher BMR doesn’t necessarily mean your metabolism is faster; a point of confusion sometimes!
  • Height. The taller you are, the higher your BMR as you have more body surface area (skin) exposed to outer elements, equating to greater heat loss.
  • Environmental temperature. People living in tropical or very cold climates tend to have a BMR around 5-20% higher than people living in moderate climates.
  • Physical activity. People who are physically active generally have a higher BMR than those who aren’t.

Increasing your metabolism

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

Firstly, exercise can increase the muscle component of your Lean Body Mass (LBM). Your LBM is made up of your muscles, bones, organs such as your 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, ie. the more calories you’re burning per day. Males usually have a higher LBM (and therefore a higher metabolic rate) than females by virtue of their larger muscles. Some female athletes, however, may have a higher LBM than a male of equal weight.

You don’t need to become super muscly 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 up your fat stores.

Secondly, exercise has the added advantage of increasing your metabolic rate for up to 24 hours after you’ve finished working out, depending on how strenuous the exercise was. So even when you collapse on the couch after a sweat session, you’re burning 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 effectively slows down your metabolism. However if you exercise as well, then you’re mostly losing body fat 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, with many promising rapid, significant weight loss in a short period of time. You often hear of an 8 kg loss in two weeks. However what you don’t hear is that about 6 kg of that weight loss is loss of fluid and muscle tissue. The overall effect is that your body becomes dehydrated and you lose muscle tissue – the very tissue you need to be maintaining and building! Soon, your body takes steps to regain its lost water and your 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, your body dramatically reduces its metabolic rate within 24-48 hours after you start dieting. The reduction in your basal metabolic rate can be as high as 45%. This is exactly the opposite of what you need to occur if you’re aiming for long-term weight control.

Repeated bouts of severe calorie restriction can actually have a drastic long-term effect on weight loss. Your body adapts to these constant periods of “cyclic fasting” by slowing down your metabolic rate to conserve energy, as it learns to worry about whether it will be fed enough at your next meal. The result is that diets become progressively less effective, and continue to slow your metabolism down.

Menstrual cycle boosts metabolism! (But not by much…)

In the two weeks before menstruation begins (i.e. after ovulation) women are naturally inclined to increase their food consumption. Biologically, this makes sense as your body is preparing for a possible pregnancy. One study estimated the increased food intake to account for an extra 500 calories per day for the 10 days leading up to menstruation. Chocolate was particularly craved during this time – a potential contributor to weight gain.

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

Smoking and metabolism

When you quits smoking, you often gain some weight even without altering your diet or exercise routine at all. This is because smoking causes your body to burn slightly more calories in order to cope with carbon monoxide and the other tobacco toxins you’re exposing it to. When you quit, your metabolism slows down to more normal levels, which means fewer calories are burned. This can lower your energy needs (BMR) by up to 200-500 calories daily.

This might sound like a good reason to continue or take up smoking. But it’s not! It’s far healthier to be overweight than to be a smoker. Weight gain when you quit smoking can be avoided by maintaining sensible eating habits and daily exercise. Exercise in particular can be very effective in countering the drop in your metabolic rate.

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