The greater the EPOC, the more total calories burned and the more potential fat loss.

When it comes to torching body fat and staying lean, what really counts is maximizing the number of calories burned after the workout (at rest), not during it — the concept of excess post-exercise oxygen consumption (EPOC), or “afterburn” for the layperson.

The greater the EPOC, the more total calories burned and the more potential fat loss. That said, it appears heavy weights provide a great afterburn.

One study showed that EPOC was higher in subjects who did low-rep sets of 80 to 90 percent of their one-rep max than it was in subjects who did sets of 15 reps at 50 percent of 1RM.

The take-home here: Incorporate relatively heavy sets in the five- to six-rep ballpark on a regular basis in addition to the hypertrophy sweet spot of eight to 15 reps. Both ranges are great for promoting muscle gains and keeping the fat off your physique.

Exercise hikes your fat burning after exercise. Scientists call this condition excess postexercise oxygen consumption, or EPOC. The more oxygen you use, the more fat you are likely to burn. We have known for years that all kinds of exercise can raise what I call your afterburn, the amount of oxygen you use for recovery, which can translate into the amount of fat calories you burn after exercise. The key has been to understand what kinds of exercise raise this value the highest for the longest period of time. The answers have been coming fast and furious, and the winner for how high EPOC can go is clearly high intensity interval training, known as HIIT.

With HIIT, your workouts will be shorter, but you’ll actually be working out at a higher intensity than when you are doing steady exercise on the cardio machines at your gym. Basically, you work out in intervals—bouts of all-out effort at a rate of 80 to 90 percent of your maximal heart rate (MHR), alternated with short stretches of active recovery. You can do any kind of high-intensity exercise to meet the guidelines of HIIT all-out effort training (e.g., sprinting outside on a track, working out inside on a rowing machine, using a stationary bike or treadmill, or even performing plyometrics) for one to two minutes. On a 1 to 10 scale of perceived exertion, your high-intensity training should exceed a level of 7. Active recovery can be the same activity but at a lower intensity (e.g., from a sprint on a track to a jog, from a twominute hill climb on an indoor bike to a three-minute flat at a level of 4 or 5, or from intense plyometrics to squats, sit-ups, and push-ups). This cycle is repeated for about 20 minutes. Plenty of research shows that HIIT is a super-effective way to burn fat.

Studies show that your afterburn rate rises exponentially with an increase in intensity during exercise. This is in contrast to a linear increase in afterburn as exercise duration increases. While steady state exercise at high intensity burns a higher EPOC compared to moderate intensity aerobic exercise or circuit training, high-intensity interval training leads to higher oxygen consumption per time during exercise, which results in the highest EPOC, afterburn. The length of afterburn has not been consistent among studies, ranging from 30 minutes to 4 hours, depending on the fitness level of the subject and the intensity and number of bouts of the training session. The more fit you are, the greater the physical challenge, but the very short duration of HIIT also limits the duration of EPOC, despite its high peak value.

And here’s something else: HIIT is a great way to burn belly fat. In a study from the University of Virginia, researchers recruited 27 middle-aged, obese women with metabolic syndrome (a prediabetic condition) and had them complete one of three 16-week aerobic exercise interventions: no exercise training (control); low-intensity exercise training (LIET); and HIIT. At the end of the experimental period, HIIT had significantly reduced total abdominal fat, and there were no such changes in the control or LIET groups. This is not to dissuade you from doing moderate-intensity training, endurance training, or circuit training. Testing has shown that if you measure calories burned during exercise, a longer duration exercise session or even a steady state high-intensity exercise session will likely burn more calories. Cumulatively over time this may lead to more total calories burned. But if your time is limited and you need to be efficient with your training, the short duration of HIIT won’t decrease your calorie-burning potential; you make some of it up in the afterburn. It’s also a great way to change up your training and add variety, which keeps you interested and more likely to stick with exercise daily. If you want to know what muscle groups create greater EPOC, just think about what it takes to recover from a leg/glute/lower body day compared to an arm/chest/upper body day. That’s your clue to the fact that working big muscles like glutes create a higher afterburn than working smaller muscles likes biceps and chest. (Believe me, I’m not judging your chest or biceps!) The big picture here is that exercise variety promotes all kinds of improvements in fitness and strength, speed, and power. Changing up your routine and adding in HIIT protocols on short days can make a big a difference to your cross-training and body-sculpting goals. Now let’s add in a little discussion about diet and HIIT, to demonstrate how recovery feeding can bump up your fat burn. Scientists in Japan wanted to know if HIIT would enhance the increase in oxygen consumption that comes from eating food, called the thermic effect of food (TEF). Ten subjects spent multiple 24-hour sessions in a metabolic chamber. HIIT exercise consisted of six or seven bouts of 20-second bicycle exercise (intensity: 170 percent V∙O2max) with a 10-second rest between bouts. HIIT was always preceded by 10 minutes of exercise at 50 percent V∙O2max. On two separate days, four subjects were fed lunch and dinner and EPOC was tested with and without exercise. Six different subjects fasted and were studied on two separate days with and without exercise. The researchers’ main finding was that HIIT enhanced a small but significant increase in diet-induced (fed) TEF during the 10.5 hours after exercise, with no comparable increase with feeding but without exercise. Eating is part of your daily routine. If you get in a HIIT workout before you eat, you capitalize on your fat-burning potential. That’s an entirely new benefit from your recovery shake or meal, so don’t skip it thinking that you’ll lose more weight. That’s like leaving money on the table!