Buzz
I’m a strong believer in tracking calories to aid weight loss. This approach can be very effective... with one important caveat. Here’s an unsettling case where simply thinking about calories could actually derail your progress.
We’ve discussed how relying solely on exercise for weight loss is likely a poor investment of your time, and a growing body of research seems to back this up. A 2011 study published in the American Journal of Medicine concluded that:
Moderate-intensity aerobic exercise programs lasting 6-12 months result in only a slight reduction in weight and waist circumference among overweight and obese individuals. Our findings indicate that standalone aerobic exercise is not an effective weight loss strategy for these groups.
As Dr. John Briffa, author of Escape the Diet Trap mentions on his blog, a 2010 study published in the International Journal of Obesity revealed that it took 35 hours of cardio without any dietary changes to lose a single pound of fat. So, exercise alone doesn’t seem to work, but why is that?
Exercise Doesn’t Increase Our Appetite
One theory suggests that exercise triggers hunger, which causes overeating and ultimately cancels out the caloric deficit created through exercise. Gary Taubes, author of the provocative book Why We Get Fat and a well-known critic of carbohydrates, claims this is the concept behind 'working up an appetite.' It's something we've all experienced, making it an understandable idea, but let's take a closer look at the research.
A 1997 study published in the British Journal of Nutrition divided participants into three groups: one engaged in high-intensity cardio, one in low-intensity cardio, and one group did no exercise (the control group). The participants were asked to rate their hunger levels and then taken to a buffet where they could eat as much as they wished.
If exercise really does 'work up an appetite,' we would expect the exercisers to have rated their hunger higher than the control group, and they would have eaten more. But neither of these outcomes occurred—there was no significant difference in hunger ratings or food intake across the groups.
This study wasn't an isolated case. Additional research, such as a study published in the Journal of Sports and Science Medicine, another study in the Proceedings of the Nutrition Society, and yet another study in Metabolism - Clinical and Experimental, all followed similar procedures and reached comparable conclusions. Participants were divided into various exercise groups and a non-exercise control group, then taken to a buffet. All of these studies showed that not only did exercise fail to increase hunger... in some cases, it even helped reduce hunger.
This raises some obvious questions. Where can I sign up for one of these buffet studies (preferably the control group)? But more importantly, what exactly is going on here?
...But We’ll Still Eat More Anyway
In theory, exercise should lead to more calories burned, reduced hunger, and greater weight loss, but that doesn't happen in practice.
Two studies offer a compelling explanation for this Scooby Doo-style mystery. While they share similarities with previous research, this time the researchers asked participants to consider exercise and food in terms of calories.
In a 2010 study published in the Journal of Sports Medicine and Physical Fitness, researchers asked participants to consume the same number of calories they had burned through exercise. However, they ended up consuming two to three times the actual amount.
In another experiment, participants were asked to exercise and then go about their day while keeping a food journal. The researchers then converted these food journals into calorie equivalents. On paper, it seemed like there was an overall caloric deficit in the group. But when the participants' final weights were measured, there was no sign of any weight loss.
These studies revealed that the participants' supposedly appetite-suppressing activities didn’t actually result in weight loss due to a phenomenon I’ve dubbed the Heisenberg Rule of Exercise:
For many, simply tracking the calories burned through exercise seems to erase the weight loss benefits.
When exercise is measured in terms of calories—the same unit as food—it leads people to subconsciously treat them as part of one big equation. In this equation, calories become a currency for extra food. For instance, someone might translate 30 minutes on the treadmill into one Krispy Kreme donut.
The issue here is that people often overestimate how many calories they burn through exercise while underestimating how much they eat. Accurately balancing calories in versus calories out is a complex skill, and misjudging these numbers can lead to food choices you might not otherwise have made.
Although exercise may physiologically reduce hunger and increase your overall calorie deficit, using the language of “calories” psychologically leads you to consume more calories than you actually burn.
And when physiology and psychology clash in fitness, psychology almost always comes out on top.
From my experience as a fitness coach, I’ve observed that those who manage to lose weight with just cardio rarely focus on calories. They simply take up a new sport or activity and begin shedding pounds almost effortlessly.
On the other hand, regular exercisers who claim their weight never changes tend to obsess over calories. These are often the individuals who feel they’ve “earned” a Starbucks caramel frappuccino after a tough cardio session.
How to Solve This Issue
It's essential to highlight that we're not suggesting that estimating calories is inherently wrong. Tracking caloric intake is an effective tool that we support. However, estimating calories burned through exercise could foster a negative mindset: viewing food as a reward for the calories burned. While this might be effective for advanced dieters, it's a strategy that fails most.
But you can still gain the health benefits—even from the calories burned during exercise—by keeping these points in mind:
Instead of calculating “calories burned” every day, try doing it on a weekly basis or use an activity factor. This approach can help prevent spontaneous eating decisions because you haven’t turned exercise and food into a “calorie” transaction.
As Dr. Briffa advises, view aerobic exercise as something you do for fun or health, not as a means to burn calories.
If weight loss is your main goal, consider prioritizing strength training as it will give you a better return on investment of your time.
As we mentioned in our Exercise vs. Diet article, bear in mind that weight loss happens primarily in the kitchen, not the gym.
Exercise should be approached with an eye on your overall health and long-term (not daily) weight loss goals. The moment exercise becomes just another number in your daily calorie tally, its purpose is lost.
Images by Kiril Yankov, Guttorm Flatabo, and Peter Mooney.
