In my last post, I explained that metabolism refers to the sum of all the chemical reactions that occur in your body.  Your metabolic rate refers to the speed at which these chemical reactions occur and is a measure of how many calories you expend.  Your basal metabolic weight refers to your metabolic rate when you are sitting and relaxed, and your total metabolic rate adds the energy you expend when you are active to your basal metabolic rate.  Total metabolic rate varies widely among individuals depending on their size, muscle mass, hormonal influences, and especially their activity level.

How active you are has a huge effect on your total metabolic rate.  One of my sons, Nathan Trimble, is a serious athlete.  In fact, he won the Houston Marathon twice in the 19 and younger category for men.  He runs and rides his bike at least two hours a day–sometimes several hours a day.  He’s not a very big person, yet he must eat about 6,000 calories every day just to maintain his very low body weight and meet his energy needs.  (When he’s home, my grocery bill goes up big time!)  Almost everyone else on the planet would quickly gain weight eating that many calories on a daily basis.

When I was in my late twenties, I joined a women’s running club.  I remember our potlucks quite vividly.  Everyone brought a lot of food, and we all dove into it like we were starving.  No one thought about counting calories, and everyone was thin!  That’s because we were all running at least 30 miles a week, plus doing interval training on a track once a week.  We were burning off the calories we ate almost as quickly as we ate them.

Exercise increases your metabolic rate several ways.  First, it increases your muscle mass.  A pound of muscle uses three times the number of calories at rest than a pound of fat.  Before you get too excited about that, muscle tissue at rest still doesn’t burn very many calories–just six calories per pound a day, but it certainly helps.

Muscle tissue burns a significant amount of calories when you are exercising, however, and your metabolic rate increases significantly, providing a huge help to weight control.  (No surprise there!)  I went on a two hour hike this weekend, for example, and probably burned over 600 calories during that activity.(1)  If I had stayed home and watched TV during those two hours, I would have burned about 150 calories.(2) Not only that, my body’s metabolic rate stayed higher after my hike as as my body repaired itself from the effort–perhaps as long as 24 hours.(3)

Understanding the effect of exercise on metabolic rate is especially important for people as they get older.  You’ve probably read that your metabolic rate slows down as the years pile on, leading to weight gain.  Research suggests, however, that this is probably due more to a drop in activity levels rather than aging.  As people get older, they tend to become less active, resulting in a loss of muscle mass and a drop in their total metabolic rate.  Older people who keep their activity level high do not seem to experience the same drop in metabolic rate as those who exercise less.(4)

I think there is something else very significant about regular exercise.  When I am faithful to exercise every day–even just a half an hour walk with my dog, I tend to be more active throughout the day.  My mood is better, I have more energy, and the quality of my sleep is much higher.  All this makes me want to move more.  I tend to bound up the stairs instead of climbing them slowly.  If I have some free time, I feel like working out in the garden instead of moping around the house.   If I do watch TV, I’m more likely to pick up my hand weights and use them during that time, and I’m more willing to say “Yes!” if a friend wants to go on a bike ride.

So, that half hour walk has a huge payoff.  I’m burning more calories while I exercise, I’m burning more calories after I exercise, and I tend to be more active throughout the rest of the day–again burning more calories.  Not only that, but I want to eat more healthily as well.  I firmly believe a half an hour daily walk can change a person’s life because of its ripple effects.

By Holly Trimble, MS, LPT

References

1.  Calories Burned Calculator [Internet]. Changing Shape; Available from:  http://www.changingshape.com/calculators/calories-burned/

2.  Calories Burned Sitting Quietly and Watching TV [Internet]; Diet and Fitness Today; Available from http://www.dietandfitnesstoday.com/caloriesBurnedInfo.php?id=141

3.  The Myth About Muscle and Metabolism [Internet]; Christian Finn. Available from:  http://muscleevo.net/muscle-metabolis#.Ut7tt7TnZaQ

4.  van Pelt, R.E., et al (2001). Age-related decline in RMR in physically active men: relation to exercise volume and energy intake. American Journal of Physiology, E281, 633-630

Disclaimer:  Nothing in this blog should take the place of advice from your own health care provider.  Anyone starting an exercise program should consult with his or her physician and follow their recommendations.

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In my last post, I shared a Ted presentation on dieting and weight loss. In that post, I repeated Dr. Sandra Aamodt’s premise that losing weight may cause the hypothalamus to slow down a person’s metabolism, making it very difficult to maintain a weight loss. I thought I should clarify the terms “dieting” and “metabolism” in this post.

To me, the term dieting means deliberately restricting calories to achieve weight loss. For example, if someone decides to only eat 1200 calories a day, that person is “going on a diet.” It makes me think of someone carefully planning each meal, recording how much he or she ate, and obsessively watching the scale to keep track of weight loss. It involves food deprivation, frustration, and suffering. Worse, dieting can lead to an eating disorder and an unhealthy obsession with food. Will dieting cause weight loss? Yes, it will, but it usually doesn’t translate to a lifelong victory over excessive weight. In fact, a person is likely to go through all that effort, only to see his or her weight eventually go back to what it was before, or even higher.

Metabolism refers to the sum of all the chemical reactions that occur in your body. Catabolic reactions break down larger molecules into smaller ones, and anabolic reactions build larger molecules from smaller ones. Think about what happens when you eat a bowl of oatmeal. Chemical reactions break down the complex carbohydrates in the oats you eat into smaller glucose molecules, using catabolic reactions. The glucose molecules that aren’t needed for your immediate energy needs get strung together to form a larger molecule called glycogen, using anabolic reactions. Millions of other chemical reactions occur in your body every day. You must make and secrete hormones, repair body tissues, get rid of wastes, process sensation, move body parts, and so on. The speed at which all of these chemical reactions occur is your metabolic rate, and you use the energy in the food you eat for these chemical reactions. If your metabolic rate is fast, your chemical reactions occur at a faster rate of speed, and you burn more calories. If your metabolic rate is slow, your chemical reactions occur at a lower rate of speed, and you burn fewer calories.

I hope you can now why severe caloric restrictions are not a good idea. They slow down your metabolic rate, causing you to burn fewer calories. When you go back to eating your usual amount of food, weight gain results.

To learn more about metabolism, here are two sites I recommend. One is designed for children, but I think it’s a great one for adults as well:

http://kidshealth.org/parent/general/body_basics/metabolism.html

http://www.news-medical.net/health/What-is-Metabolism.aspx

In my next post, I’ll talk about ways you can keep or increase your current metabolic rate.