As my most astute readers already know, I don't think that exercise – especially cardio – in and of itself is a very viable solution to weight loss. In fact, I'd go as far as to make the argument that exercise is not necessarily for everyone just starting out with fitness.
Now, I'm probably in disagreement with 99% of the population here (which should tell you something about going against the grain, since I probably get the top 1% of results from sedentary individuals), but I'm not alone.
Yet, I've also met a non-trivial amount of people in the wild who claim to have lost weight with exercise – mostly cardio – and no explicit dietary intervention. (I can only name one person who claims that she dropped a considerable amount of weight from strength training alone with no dietary intervention.) These stories cannot automatically be disregarded.
Naturally, this got me thinking. Is there a certain cohort out there that successfully loses weight from exercise alone? If so, what's different about them?
The Main Argument – Exercise Leads to Overeating
Before I move on, it's important that I clarify two things here.
1. I am talking about the general population here. For fitness coaches who read this blog, I am talking about your clients, not you. I should hope that anyone reasonably experienced with fitness knows how to lose fat via aerobic activity.
This is important because...
2. I am talking about exercise without explicit dietary intervention. That means we're assuming the individual does not meticulously plan their calories/macros throughout the day, then tack on an additional caloric deficit from cardio. Rather, the individual is allowed to eat ad libitum, or as much as he or she wants. Remember, no one is arguing the laws of calories here. We're interested in what will happen to Average Joe when left to his own devices.
The underlying assumption that powers the "inefficacy of cardio" argument is that exercise leads to hunger, hunger leads to overeating, and overeating leads to negating the caloric deficit that you created in the first place.
Infamous carbohydrate-demonizer Gary Taubes has a "stump speech" (I say this intentionally because fitness factions and political factions are eerily similar) where he's all over this argument like me at a sushi buffet. Taubes goes into his folksy propaganda about how Ma always talked about "working up your appetite" after running around the school yard.
At any rate, it's a believable claim. Who doesn't remember a time that exercise made them hungry? It's certainly corroborated by the people that I see in the elliptical section of the gym day after day, without any noticeable weight loss.
But is this the reason that cardio alone does not seem to cause significant weight loss – as evidenced in this study, where it took up to 40 hours of moderate intensity aerobic exercise to lose 1 pound of weight?
Let's look at some existing research.
The Impact of Exercise on Hunger
One study broke out participants into three groups – one that underwent high intensity cardio, one that underwent low intensity cardio, and one that did no exercise (i.e. the control group). It then asked the participants to rate their hunger, fullness, and consume food ad libitum. If exercisers truly "worked up an appetite," then one would expect a significant responses and/or food intake above the control.
There were no differences above the control (no exercising) group for any of these variables.
Surprise surprise. Exercise did not lead to additional caloric consumption.
It's worth noting that there was a difference between high intensity and low intensity groups when you look at the net energy balance (intake minus the amount expended), in which case high intensity exercise won out.
In almost every way you sliced it – whether looking at ad libitum food intake or measuring hunger/satiety hormones like ghrelin and polypeptide YY – exercise only seemed to help curb hunger.
Evolving Your World View – A Quick Tangent
Similar to what I encountered above, there will come a point when you cannot reconcile your current world view with new, credible information.
Everyone will face this at some point. Unfortunately, however, almost everyone will completely disregard this conflicting data in order to shield the lens by which they view the world.
World views are very personal things. They're forged through experiences, often very personal, irrational ones that are heavily tied to your sense of self-worth. To invalidate one's "lens" is to invalidate his or her identity.
As a personal example, I've helped many people who could not lose weight with exercise alone. Instead, I helped them conquer fitness instead, in a cerebral way; it's how I've built my brand as a coach.
It's easy to see how a body of credible evidence, one that directly contradicts my mental model of fitness, could send my self-esteem crumbling down. The natural reaction is to hold even more tightly and protect my existing view at all costs.
I'm going into a bit of a tangent here, but I want to note that it's important to constantly evolve your world view by iterating your model of how things work. Not just with fitness, but with all things.
Don't be like Gary Taubes or creationists that cling on to their beliefs at all costs. Rather, allow the way that you view the world to be malleable. Be open-minded. Be humble. Be curious.
And above all else, be brave enough to be wrong.
By automatically recoiling from contradictory information you lose the chance to sharpen the very same lens that that you were trying to protect from shattering.
If I recoiled rather than refined, I would have lost the ability to come up with a better mental model of how people react to exercise – one that separates psychology from physiology – in particular how everything changes when people measure.
The Heisenberg Rule of Exercise
There are two interesting studies that give us a hint about what's going on.
One study was similar to the previous ones that I mentioned, but different in a very important way. As with the previous studies, participants were made to exercise.
However, this is where it differed. After their activity was over, they were then told to eat the caloric equivalent that they burned through exercise. They ended up eating 2-3 times more energy than this amount.
In another study, participants were made to exercise, and then left to their own devices with regards to food intake. Instead, they were told to keep a food journal, which was then translated into caloric values by the experimenters. On paper, it appeared that there was an overall caloric deficit throughout the group.
However, when participants' final weights were measured, there was no evidence of weight loss.
The explanation in a nutshell is this. I call it The Heisenberg Rule of Exercise. (Ok, it only very loosely parallels Heisenberg's Uncertainty Theorem, but I wanted to drop the name Heisenberg, OK??)
Here it is.
In your average person, the simple act of measuring exercise is what ends up sabotaging your weight loss.
If people kept their dietary habits the same and incorporated exercise, the combination of increased energy expenditure and decreased acute hunger would ostensibly create a caloric deficit suitable for weight loss.
But most people don't think like that.
The fact that exercise and food can be translated into the same currency – calories – causes people to subconsciously place them into one giant ledger. In this ledger, calories are the currency that affords them lifestyle choices. Thirty minutes on the treadmill might translate into one Krispy Kreme, for example.
The problem here is that human beings are horrible at this skill. It's one that can only get better after years of refinement.
Even if you do develop this skill, the act of translating your exercise into calories may persuade you to make food choices that you might not have made. (This is why it's best to build exercise into one's caloric multiplier.)
Sure, physiologically, exercise may not increase one's caloric consumption. But psychologically, we can see how this is feasible. And in the domain of fitness, when physiology and psychology go head-to-head, psychology will always win out.
My own personal experience as a coach seems to support this model. Those who lose weight from cardio alone almost seem to stumble upon it by accident, like finding a twenty-dollar bill in your pocket. They enjoyed a sport or an activity and reaped the benefits of weight loss.
Conversely, it seems like I'm always encountering someone who "cannot manage to lose weight" only to find out that he or she takes the elliptical calorie readings at face value and goes to Starbucks some time after the gym.
I cannot be fully sure if these personas are entirely exaggerated in my own head. They might be. But they are consistent with the model above.
If you do cardio, incorporate it into your regimen. Don't translate it into calories or currency. Rather, enjoy it as part of the overall process in your fitness journey.
Need more help? Train with Dick or contact him at richard at fitocracy.com.