Tuesday, July 21, 2015

Back to Basics: Calories, Metabolism and Energy, What Do They All Mean? Part II

If we look at the term metabolism and its true definition which is: "the sum of all chemical reactions within the human body needed to sustain life" one may be confused as to how it relates to weight loss and energy expenditure. So what does this definition mean and how does it relate to fitness & health? 

Typically when we talk about metabolism we describe it as a way to measure our calorie expenditure throughout the day (For more on calories check out our part I of this series) or a way to assess our body's overall energy balance. Energy balance is essentially the sum of energy intake versus energy expenditure (aka our metabolic activity for the day).  In this case energy intake is everything that you eat or drink that has a certain amount of energy stored within it aka caloric content  Calorie expenditure on the other hand, gets a bit more complicated. The amount of calories we burn in a day can be broken up into several components. First of all we have our basal metabolic rate which is the absolute baseline number of calories that we expend just to stay alive.  This is the sum of all the chemical equations and processes that help us breathe, think, circulate our blood etc.

A step above this is our resting energy expenditure which is the maintenance energy cost of the body at rest, under steady state conditions (rested and fasted) which makes up about 60-70% of all the calories we burn in a day. We also have thermogenesis which is the amount of calories expended through digestion and absorption of food.  Then we have our daily activities / movement and exercise which can make up anywhere from 10-20% depending on how active you are throughout the day or if you are engaged in several hours of training a day such as the Tour de France or Two-a-days. Most people are surprised to hear that their daily trip to the gym really doesn't account for a large portion of their calories expended for the day.  So why does this matter? Anytime we are talking about gaining or losing weight we have to look at it in terms of our overall energy balance. As you might expect, if we are trying to lose weight we need to be in a state of negative energy balance or burn more calories than we consume at the end of day. It's really that simple. Of course the type of calories you are eating plays a role but the overall energy balance is really the most important part.  On the other hand, if you are trying to gain weight (hopefully you are trying to gain lean muscle mass only) you need to be eating more calories than you are expending throughout the day.

How do you increase your metabolism?
Most people are probably more interested in how to lose weight and therefore may be wondering how than can increase their metabolism. Well first of all you should look at the easiest component of energy expenditure to manipulate and focus on that one which happens to be physical activity and exercise. This is something than you can change on a day to day basis and start immediately. There's no secret here, just moving around more in general throughout the day will help increase your calorie expenditure in addition to adding in bouts of high-intensity exercise as it appears to have a greater stimulatory effect on your post-exercise metabolic rate. 

Also, if you are to able to increase your resting energy expenditure you can automatically burn more calories throughout the day just by resting (doesn't get any easier than that does it?!).  The best way to increase your resting energy expenditure is by increasing or maintaining your lean muscle mass as it is an active tissue that helps you burn more calories. There is a direct correlation between resting energy expenditure and lean muscle mass.  This is why athletes and physique competitors are able to eat 6,000 calories per day and still maintain an 8% body fat.  Because of this, strength training and high-intensity interval training or both such as P90x or T-25-type workout programs can be a beneficial tool for weight loss as you burn energy during the workout and they help you to increase lean muscle mass. 

Stay tuned for next time when we cover different ways to assess your daily energy requirements in order to provide you with a starting point in your body composition management.

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