Two questions often come up around weight loss and diet: “How much should I exercise?” and “How much should I eat?”. Eating enough without eating two much is important for everybody for a variety of reasons, weight being only one of them. So how much food does a person really need? The simple answer is that you need to eat enough to replace the calories you burn to maintain your current weight. However, this is a multi-variable situation, and the simple answer leads many people to try destructive or intuitive but counter-effective ideas.
The rate at which a body burns energy is called metabolic rate. This has two parts: resting and active. Resting metabolic rate is a measure of calories burned when stationary; active metabolic rate is the calories burned through activity. At any moment, the two added together is the current metabolic rate. The amount of food consumed and then burned is called energy flux; eating more and living more actively is an example of high energy flux, whereas eating less and living a less-active lifestyle (common in Americans and especially in dieters) is low energy flux.
Metabolic rate is affected by many factors. One obvious factor is how much a person exercises and is active through the day and over time. Activity burns calories directly, so exercising will increase your metabolic rate while the exercise is going on. Other significant factors are the amount of lean muscle a person has and how much a person eats.
During the day (and night), muscles burn energy at a faster rate than fat. A person with a muscular body will burn more calories doing everything, including sleeping, than a person of the same weight but with more of that weight stored in fat. Exercise, especially strength training, will raise the muscle mass.
Eating more will also increase the number of calories a person burns, to a point. This is most obviously seen through counter-example: eating below a certain amount per day leads the body to go into ketosis, or starvation mode. When this happens, the body tries to store every last calorie it can as fat. Additionally, energy levels drop to save energy, so the person is less likely to be active in little ways through the day. Finally, the body consumes muscle to acquire the additional calories needed, which leads to fewer calories being burned tomorrow and beyond. A higher energy flux has also been shown to be better for the heart than a low one. This means eating less is not the way to protect your heart; instead you should exercise more.
One thing that does not affect metabolic rate is age. While it was believed for a long time that metabolic rate dropped as a person aged, this has been proved false. Instead, the factors discussed above are the real culprits: over time people tend to exercise less and lower activity levels, reducing lean muscle mass and daily calorie burning, and change their eating habits in ways that lead to higher fat stores. You can’t blame getting older for having a hard time keeping the weight off.
A high metabolic rate is the most desirable long-term state. To keep your metabolic rate high, simply stay active: walk, run, ski, swim, and whatever else you enjoy, and you won’t need to worry very much about how much you eat. If you want to lose weight, make sure you are active above all else and the pounds will come off more easily.
Resources:
- Burning Calories Anytime [www.webmd.com]
- Exercise May Be Better Than Diet for Heart [www.webmd.com]
- The Effect of Low-calorie Diets on Metabolic Rate [www.medscape.com]
- Why does your metabolic rate drop as you age? [www.thefactsaboutfitness.com]
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- Don’t let your boss read just the headline: Can stress actually be good for you? [www.msnbc.msn.com]
- Who says our eating habits aren’t that bad? ‘Double Diabetes’ a New Threat [www.healthday.com]
From the editor
I arrived in Anchorage for a family visit and was immediately shocked by temperatures of ten below zero. I decided to run inside instead of brave the weather. As I run away the miles on the treadmill, I remember why I prefer running outdoors.
It wasn’t always that way: I used to prefer the treadmill. After all, there was no weather, no hills, and I could watch TV. Oddly enough, these are now precisely the reasons I prefer running outside: there is weather, hills, and I’m connected to my environment instead of zoning out. Now when I see someone running with their iPod, I feel sorry for them, knowing they don’t realize what they are missing.
I’ll be in warmer climes in a week, and I can’t wait. I want to run outside again.
Healthy thoughts,
Jeff
