Let's talk "metabolism." We hear about it all the time. Products and exercises promise to "rev up" our metabolism. Certain foods even! The supposed experts have us picturing out bodies idling likes car engines, waiting for someone to mash on the gas pedal - zooming our way to skinnier, happier lives.

Yah, not.

Here's the deal. Metabolism is just the sum of our chemical and physical processes. Within that definition we have catabolism and anabolism. Catabolism is to "break down" and anabolism is to "build up" (think anabolic steroids). Most of us have been brain-washed to think of metabolism as "fast" or "slow." I'm sorry, but those chemical processes are building and destroying, all day, every day, at the rate they just do it. There might be a lot of it going on, or not so much - but fast or slow isn't really the right way to think about it.

Let's modify that "fast/slow model." How about metabolism simply being how much we need? A big SUV needs a lot of gas. A little Smart Car doesn't need so much. We don't say the SUV is fast or slow. We just think miles per gallon. We might be able to tweak the engines here or there and force them to use more or less fuel, but will we turn the Smart Car into the gas-guzzling SUV? Nope.

Same with us. I don't care what I do; I will never be able to put away the same amount of food as a football-playing, teenage boy in a growth spurt. That kid can shovel in 3,000 or 4,000 calories a day and still claim he's starving. I'd weigh 500 pounds. If I completely dedicated myself to a specific lifestyle, full of hours in the gym, running several miles, staying on my feet, and closely monitoring how I spent my calories, I might be able to consume 2,500 calories a day and still look "reasonable." That's pushing it, plus I don't want to live that way. My better strategy is to figure out how much I actually need, and just stick to it (or below it).

Our energy needs are made up of three components: resting metabolic rate (RMR - what we'd burn if we just stayed in bed all day), physical activity (purposeful exercise, fidgeting, grocery shopping, yard work, etc.), and the thermic effect of food/feeding (TEF - the energy needed to eat and digest the food). Of those three, your highest level of control is physical activity. The other two are more difficult to impact, if at all. You might get an extra 100 calories a day, give or take, from food choices and the addition of lean muscle-mass, but that's about it. If you need to lose 20 pounds, and assuming you've decoded how to wring out those 100 calories, you'd be waiting 700 days to lose your 20 pounds. Your better strategy is to focus on the physical activity and take in less food. Let the RMR and TEF be what they'll be.

Stop obsessing over negative-calorie foods, pills and weird exercise gadgets that claim to boost your metabolism. I am what I am, and you are what you are. Work within it.

• NSCA certified personal trainer Shannon Sorrels holds a bachelor's degree in chemistry and an MBA. Her company, Physix LLC, works with Valley individuals as well as groups to improve their overall fitness. Reach her at (480) 528-5660 or visit www.azphysix.com.


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