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Metabolism is a complex process misunderstood by those who perpetuate the myths that make weight loss more difficult for the rest of us. Here are 4 facts about our metabolism not well understood by these weight-loss experts.
1. Metabolism and Aging
We’ve heard it, maybe even said it. The moment we turn 30 (or some magic age) our metabolism takes a dive. The reality is that our metabolism doesn’t take a dive — it’s our physical activities that drop.
If human metabolism does slow as we age, it is by a very small margin, practically insignificant in the context of the real world. How insignificant?
Take for example: as compared to the metabolic rate in her twenties, a woman’s metabolism in her 50s burn only 4 calories fewer per hour. Though that’s interesting on paper, it’s a difference of only a stick of gum in the real world — which barely justifies the perpetual conversation about diminishing metabolism. All this woman has to do in the span of 30 years is take a couple bites fewer at dinner and go for a walk around the block.
[Besides, studies determining calorie expenditure in aging were based on normal-weight subjects that might have exhibited the natural loss of weight from diminishing DNA expression associated with getting old.]
2. Eating Less and Metabolism
In the weight-loss world, it is warned that weight loss by reducing calories could slow the metabolism.
Consider this: it’s been demonstrated that animals within the same species (including humans) having similar body sizes possess nearly identical basal metabolic rates — the basic metabolism required to merely stay alive. The larger the animal, the higher the metabolic rate, regardless of whether that size is mostly fat or lean tissues.
In other words, an obese man wearing an XXL shirt has nearly an identical basal metabolic rate of that in a lean man wearing the same-size shirt. (And, naturally, a third man wearing a medium-size shirt has a comparatively lower metabolism.)
A simple mathematical model can be used to predict basal metabolism — in other words, simple body weight (instead of body size) can approximate basal metabolism.
Metabolism is, therefore, an approximate reflection of body size. As we lose weight or size, our metabolism also decreases, regardless of muscle-to-fat ratio. This is a natural result of changing energy dynamics in weight loss, and is often misinterpreted as metabolic slow-down associated with calorie reduction.
When we weigh less, our metabolism is naturally lowered. That’s a good thing, not a bad thing. And a lower metabolic rate does not make us overweight — overeating and under-activity do.
3. Muscle Mass and Metabolism
A reduction in metabolism during weight loss is thought to be a result of muscle loss. But when we put into perspective the relative contribution of muscle mass to metabolism, we see that this is bunk.
Muscle mass contributes only 25% to the overall basal metabolic rate (Berne, 1998).
- Kidneys – 200 cal per pound
- Heart – 200 cal per pound
- Brain – 109 cal per pound
- Liver – 91 cal per pound
- Muscle – 6 cal per pound
- Fat – 2 cal per pound
The decrease in resting metabolism is associated with the natural reduction of overall tissue types, and not just of muscle.
4. Breakfast and Metabolism
Contrary to what we’ve been told, the metabolism doesn’t need a “kick-start” with breakfast. The metabolism responds to movement and energy demand. Just getting out of bed is a good kick-start.
The best “kick-start” to the metabolism, however, is (and will always be) exercise. But we can do that at any time of day.