You've probably heard this one before... Cut out a mere 100 calories per day and you can lose 10lbs in one year. It sounds so magically enticing. Who couldn't find 100 calories in their day that they wouldn't even miss? Or perhaps you've heard that by cutting 500 cals/day or burning an extra 500 cals through exercise you can lose ONE POUND PER WEEK. Wouldn't that be wonderful?! But it's myths like this that leave people feeling frustrated and depressed when their "simple diet plan" doesn't work. Absolutely no one who reduces their daily caloric intake by 100 calories per day will lose 10lbs in one year. I promise you, it doesn't work. "But it's the law of thermodynamics!" The talking heads proclaim. "It has to work!".
Yes, 1lb of fat represents approximately 3500 calories of stored energy.
Yes, 100 calories per day x 365 days per year = 36,500 calories which amounts to 10.4lbs of fat.
Yes, 500 calories per day x 7 days per week = 3500 calories, the equivalent amount of energy in 1lb of fat.
And yes, calories in = calories out +/- calories stored.
We agree, the human body is not a magical place where energy is created or destroyed. The math seems so beautiful, so simple, so undeniable. And yet, not even one single participant in any dietary intervention study anywhere has ever lost the amount of weight predicted by formulas like these. So why the heck doesn't the simple math, addition and subtraction strategy work? The main flaw in this argument is a basic assumption error in the math. For the conclusion to work, you have to assume that "calories in" is a known variable and that "calories out" is a constant. You must assume that you know exactly how many calories you eat and that your body burns precisely the same number of calories every single day. But there are problems on both fronts...
Unknown variable - the amount of calories you consume is
not a known variable. Most of us don't bother to count and for those that do the results aren't much better. You can be as anal as you want about weighing, measuring, and counting calories and you will never be precise enough each day to err by less than 100 calories. Even aiming for a 500 cals/day deficit gives you more wiggle room, but the results are no better. That kind of precision is impossible. Was the chicken breast pure chicken, or was its weight plumped up with a salt water solution? Was that apple a small 70 calories or a large 95? You cooked with 1TB of olive oil, but did you eat it all or did some stay in the pan or on your plate? What about the
things that do come with nutrition labels? One study concluded:
"On average, the calorie content information provided by the restaurants was 18 percent less than the researcher's calorie content analysis. Two side dishes exceeded the restaurant's reported calorie information by nearly 200 percent. The calorie content information reported by packaged food companies averaged 8 percent less than the researchers' analysis."
10 or 20 calories here or there adds up to a huge margin of error each and every day. Trying to figure it out is a fool's game.
The Dependent variable - the amount of calories you burn is not a constant. In fact it fluctuates wildly in response to many factors, including how much you eat (and more importantly, what you eat). "Calories out" is influenced by "calories in", making it not a constant, but a dependent variable. The reason the 100 cals/day (or 500) caloric deficit plan doesn't work is the same reason that severely calorically restricted starvation diets stop working over time: the body adapts. Less energy is available? No problem, says your body, less energy is burned. Balance is restored. All is well. Your body has tons of options to conserve a few hundred calories per day. A general feeling of lethargy can get you to take the elevator instead of the stairs or stay on the couch instead of go for an evening stroll. A slight drop in body temperature saves energy just like turning down the thermostat in your house. There are many other metabolically expensive processes that can be slowed or shut down completely. And then there's appetite. Cells that need energy will compel you to eat food. An extra bite here, a few almonds there, and poof your caloric deficit is gone. What are we supposed to do then???
Tomorrow, part II talks about using the energy balance equation to your advantage and working with your body rather than against it.