This article is to be published in the Candian Science Writer’s Association blog and is accordingly non-inflammatory. Sorry.
There is an ancient Greek fable about Sisyphus, a malevolent king who was punished by the gods in the form of a perpetual fruitless task – he was to push a boulder up a hill only to have it roll down ad infinitum. One can’t help but make the comparison to Sisyphus and his eternal battle with going nowhere and legions of desperate gym-goers and yo-yo dieters who end up not gaining an inch in their journey and often end up gaining pounds.
So is it Jill Michaels to the rescue? Dr. Atkins? Nope, it’s a basic understanding of metabolism.
The first thing to consider is concept we all know well: excess calories from food will inevitably form fat stores in unsightly areas.
The second thing to consider are processes people are vaguely familiar with: our basal metabolic rate and daily metabolic rate. A more in depth understanding of the interplay between our fat storage process and our energy use processes will quickly expose why going to the gym to burn fat is very inefficient.
First, as a caveat for all that follows, declaring that working out to lose fat as inefficient in no way declares that physical activity is useless. Physical activity is an essential component of health and well being; after all, we are built to move. Numerous studies have illustrated the benefits of physical activity in curtailing many of the diseases of affluence that torment us today, including diabetes and coronary artery disease. It’s unfortunate that conventional wisdom has conflated physical activity and it’s positive effects with efficient fat loss.
Let’s return to our friend the basal metabolic rate, or BMR. It’s defined as the amount energy needed to sustain basic life processes at rest. The most intuitive way to think about it is the energy you use to sustain yourself at 4 am in the morning, when you are fast asleep and when you are in a fasted state (i.e., you haven’t eaten in a while and your body isn’t dedicating any energy to breaking down food).
So while you are sleeping, powering your brain, liver and skeletal muscle represent 60% of your total energy needs (20% each), while your heart and kidneys total 20% of your energy needs (10% each) and 20% is dedicated to miscellaneous processes.
Clearly, your body is busy at work even when you are not. So what does this work entail? Definitely not moving around. Imagine yourself at 4 am in the morning. You might toss and turn a little bit, but for the most part you are stationary.
The energy used by your organs while you are at rest manifests in a number of processes; a number or processes that we don’t typically imagine when we think of energy use. In fact, roughly 90% of this energy use if for biochemical reactions! This includes anabolic reactions (e.g, building proteins from amino acids) catabolic reactions (e.g., breaking down glycogen to glucose). In addition, it entails maintaining ionic gradients within the cell, mostly in the form of the Na+/K+ pumps and Ca+ channels that sit in the cell membrane. To tie together the picture more clearly an a good example will do. A single neuron in the brain primarily uses glucose to supply ATP for all of it’s biochemical reactions. It might get its glucose supply from the breakdown of glycogen to blood glucose (a catabolic process). The ATP derived from this glucose supply is used in to synthesize proteins essential for the cell’s functioning (an anabolic process). Two such proteins are the forementioned Ca+ channels and Na+/K+ pumps. To power these channels and pumps, more ATP is needed. This may be hard to follow, but it’s pretty clear this picture of energy use, which encompasses 90% of energy use at rest, has nothing to do with contracting muscles to put your body in motion!
It’s easy to dismiss energy use at rest if you are predisposed to thinking of energy use in terms of moving around, be it walking, running, lifting weights or shoveling your driveway. After all, your energy use while sleeping is one thing, and that 90% figure is pretty significant, but when we wake up and get going, the energy we use for activity clearly amounts to more than the energy we use for biochemical reactions.
This is where we need to flip our intuitive notion of energy use upside down and face the facts. The total energy expenditure for a physically active person (the type that might go to the gym 3-4 times a week, hit the elliptical and read Cosmopolitan magazine) is ~2500 calories. Of that 2500 calories, only 30% is used for physical activity, including the energy used spending an hour on the elliptical. Another 10% or so is used to process food. That leaves 60% of energy use for our basic life processes, the same ones at rest processes described above. It doesn’t take a doctorate in advanced mathematics to see that 50% of the energy we use, even if we religiously go to the gym, is used for microscopic biochemical reactions.
Clearly, sitting there and doing nothing still requires more energy than you could reasonably use while working out! Now, let’s go back to the first idea. Fat storage represents a mismatch between energy availability and energy use. It’s a valuable tool evolutionarily – just ask your friendly neighborhood grizzly bear who eats as much as possible during times of plenty to store fat for sustenance during hibernation. While hibernation is an extreme form of energy scarcity, fat stores equip animals for times when there is nothing to hunt or nothing to graze on. In fact, fat storage largely developed as a response that anticipates periods of starvation. It’s primary function is to fuel the body, including all those microscopic biochemical processes, when there’s nothing to eat.
It’s a simple relationship: eat food to build fat stores, don’t eat food to deplete stores. The majesty of this relationship is that it applies to humans just as much as it applies to your foraging deer when the grass isn’t all too green or your wolfpack on the hunt when prey is elusive or scarce. Again, this turns conventional wisdom on its head: don’t we need to eat every day to fuel our body? Resoundingly: no, no and no! For 99% of our evolutionary history, we ate irregularily with times of feast and times of famine, and we adapted accordingly. It’s no compromise to your health to go without eating for a day or two – it’s a pattern of behavior that is in line with our evolutionary design, unlike eating 3 meals a day on fixed intervals. And in this day or two of not eating, your body is using your fat stores primarily to fuel processes that having nothing to do with moving around! Efficient fat loss in modern society becomes a battle of the will: can you overcome the subjective feeling of hunger and lay off eating for a day or two in between days of regular eating?