Your body caps your daily calorie usage
While the word calorie gets thrown around a lot in our daily lives, many of us don’t really appreciate how they actually matter to our bodies. Somehow we go from the energy needed to heat a gram of water one degree to a certain number of calories per day to a salad slathered in ranch dressing and fried chicken, and it’s not clear how all this is supposed to work. Even if you try to balance how much you eat with how much your body needs to use in a given day, that comparison can get muddled pretty quickly, because it seems that there’s a cap on how much energy your body wants to use on any given day, regardless of activity.
To do perform any the huge variety of tasks it takes on, from breathing to running up the stairs, your body needs energy. Even seemingly idle moments still require a minimum caloric investment to keep your body’s systems function, like the 68 calories a 150-pound adult uses just to sit quietly in a chair. More strenuous activities require more energy as you’d expect, such as when that same adult uses 102 calories to jog for 15 minutes. While this seems like it should scale up in a linear fashion, our metabolisms didn’t evolve in times of candy bars and french fries. Our ancestors were probably much more concerned with efficient use of energy, rather than trying to shed excesses of it, and researchers have found that our energy usage plateaus past a certain point of activity.
When does more activity use more energy?
Researchers measured this pattern across the world, among varying peoples and lifestyles. Possibly due to more efficient, stronger muscles and tuned metabolisms, the amount of energy used to go from moderate to strenuous activity didn’t change much. An extra hour at the gym didn’t mean you were burning a lot more calories each day, as long as you went to the gym somewhat regularly. The big jumps in energy usage were found around lower activity levels. It takes a lot more energy to go for a walk rather than sit on the couch, but once your body is used to regular walks, switching to a job might not eat in to your energy reserves as much as you’d think. As long as you’re not exercising strictly for calorie-counting, this is fine- you can still benefit from a variety of other health benefits associated with stronger bodies, and there’s next to no chance that you’ll really be over doing it.
Source: Fitness fiends take note: More exercise does not mean more calories burned by Andrew Joeseph, Stat