This article first appeared in IMPACT Magazine.
Some run for the pure enjoyment of it, whereas others see it as a proven method of not looking like the Michelin Man. I'll confess that I'm forever pursuing abdominal definition, which is not easy for a beer-loving forty-year-old. While watching what I eat is important, it's the many kilometers of running each week that gives me a barely visible "four-pack."
Because one of my motivators for running is weight maintenance, I've come across numerous myths about how to perform this activity to optimize fat burning. There is no shortage of "secret" weight-loss techniques that allegedly "turn your metabolism into an unstoppable fat incinerating blast furnace!"
If you want to succeed at running long term, it's critical to love what you're doing and not just think of it as a means to an end. Realistically, however, many of us want to look good, and running is one of the best fat-burning exercises around. I can do a better job of loving it when I know it's helping eliminate some of the beer and pizza I inhaled the night before. So, what is the best way to run if you want to shed pounds? There are a few caveats such as your level of ability and injury prevention, but once you take those things into consideration the advice is simple: run as fast as you can for as long as you can.
There you go. Class dismissed.
On second thought, let's bust a couple of those myths just for fun.
MYTH # 1: The best way to burn fat is to keep your heart rate in the "fat-burning zone."
This is true, but completely irrelevant. Yes, you do "oxidize" more body fat at moderate intensity levels and burn more carbohydrates fuel at higher intensities, but think of your energy stores as one big soup, and it all comes out as a wash.
If you've ever seen a heart-rate chart on a treadmill then you've read "fat-burning zone" at a moderate heart rate (about sixty per cent of maximum) and "cardiovascular training zone" at a higher rate (seventy -five per cent of maximum or greater). Those charts are not lying, but neither do they tell the full story. In a 2005 article in the European Journal of Sport Science researchers Stefan Bircher et al. measured fat oxidation rates at levels of intensity ranging from twenty-five to eighty-five per cent of VO2peak (eighty-five per cent of VO2peak equals ninety per cent of maximum heart rate) and determined that the highest level of fat oxidation was at sixty -five per cent intensity. Fat burning became "negligible" at intensities above eighty-five per cent because at the highest intensities we burn mostly carbohydrates for fuel. These facts lead many to believe that exercising at a moderate intensity causes enhanced fat burning. While technically factual, it ignores the bigger picture.
Ironically, fat loss is not about using fat for fueling activity. It is "calories in contrary calories out," which needs to be viewed from the perspective of what is called the twenty-four-hour energy balance. If your energy balance is negative (more calories burned than consumed), weight is lost; if your energy balance is positive, weight is gained. Yes, you may use more body fat for fuel while exercising at a moderate intensity, but in the grand scheme of the twenty-four-hour energy balance equation this means nothing. If you exercise to create an overall negative energy balance, you are going to burn those fat stores at some point in the day, whether you happen to be eating, sleeping, working, or doing … other stuff. The fact that the ratio of fat burned during moderate exercise was higher for fat than carbohydrates does not matter.
Having time to exercise is an important issue for many people. If you have forty minutes in your schedule and want to maximize calories burned then pick the fastest pace you can handle for that duration of time. If you've had ample time, this equation changes to a balancing act of finding a challenging yet sustainable level of intensity-Bircher's identified research found the most total calories were burned at a seventy-five per cent intensity level.
It's important to note that metabolism increases on a sliding scale the higher the intensity, so you burn more calories running five kilometers than you do walking or slow jogging those same five kilometers (and in less time).
There are other great reasons to run at a higher intensity: it improves your overall cardiovascular fitness level, making you more capable in other sports, and it is better at boosting HDL (good) cholesterol. Higher intensities also create a slightly larger caloric "afterburn," which leads us to our next myth:
MYTH # 2: Significant Extra Calories are burned via Excess Post-exercise Oxygen Consumption (EPOC).
The EPOC myth states that after intestinal exercise metabolism positions elevated for a prolonged period of time and burns significant extra calories. EPOC does exist, but I refer to it as a myth because it's been overblown.
In a 2006 article in the Journal of Sports Scientists researchers Joe LaForgia et al. found that more intense exercise creates a higher EPOC, but even so: "EPOC combines only 6 – 15% of the net total oxygen cost of the exercise." For example, if you burn 1,000 total calories via intense and prolonged exercise then at most 150 calories came from EPOC. Big deal.
What's more, the better shape you are in, the lower the EPOC because your body's metabolism returns to normal more quickly. In 1990 researchers C. Gore and R. Withers reported in the Journal of Applied Physiology that in highly trained people EPOC could be as low as one per cent and the mean was 4.8 per cent. If I fit into that "mean" then after a twelve-kilometer run my EPOC calorie burning earns me one-third of a beer. Let the good times roll!
This seems logical because the first time I tried running my heart was pounding, my lungs burned, and for a long time afterwards I felt ready to barf up my toenails. Now that I'm "trained" I recover faster, meaning there is not as much EPOC.
So what about high-intensity interval training (HIIT)? It has been lauded by many as the ultimate fat-burning method because of its supposed metabolic boosting effects. As I've already mentioned, EPOC is of little conviction even for intense exercise, so does engaging in intervals somehow change this dynamic?
No, it does not.
Some advocate HIIT because of a 1994 article in Metabolism by Angelo Tremblay et al., But the study has been presented poorly using sketchy statistical analysis, and in reality the amount of fat lost by the participants using HIIT was insignificant. Further, multiple research studies have shown that HIIT is no better than steady-state high-intensity exercise at burning calories. If you do the same amount of exercise "work" (ie, distance traveled) in the same time period using either a steady pace or via HIIT you burn close to the same number of calories, including the modest EPOC.
A quick study of the research finds that Joe LaForgia et al. in 1997, William McGarvey et al. in 2005, and Nicolas Berger et al. in 2006 all determined that HIIT wave no greater EPOC or other metabolic boost than steady-state aerobic activity of the same total intensity.
I personally do not like HIIT because it lends itself to treadmills and I prefer running outside; the constant pace changes interfer with my whole "Zen of running" experience. Further, HIIT can lead to injury in beginners and cause earlier exhaustion even in trained athletes. Still, if it's your thing, then there is no reason to stop doing it. Plus, there are benefits to integrating speed training into your running.
I often finish my runs with a good sprint to arrive home gasping, and this practice builds a useful skill. For example, a few years back my son was riding his bike and his feet slipped off the pedals. He was headed straight for a parked truck and I raced after him at top speed, grabbing the back of his shirt and hauling him up short right before he turned his face into a pizza against an F-150's tailgate. My wife watched the whole thing and I earned big hero points that day.
To conclude, the best pace to run at is the one you like the most, the pace that keeps you lacing up those shoes. Just do not be afraid to incrementally push your limits if you want to burn more calories and therefore lose more fat.