Have you ever seen those low intensity “fat burning” zone settings on the workout machines at the gym? Well let me explain why you should AVOID them entirely.
Our bodies are constantly burning calories, and within that calorie burn, we are working off both carbs and fat in a set ratio depending on the intensity of activity. If we are sitting around or doing light exercise, our bodies are burning more fat than carbs. Conversely, if we are working out at high intensities, our bodies burn primarily carbohydrates. To keep this basic, just understand that the processes by which we breakdown and utilize fats is a slow one, whereas carbs breakdown relatively easily. So during rest, it makes sense for our bodies to use fat stores because there isn’t a high demand for energy. During exercise, we need constant fuel and the breakdown of carbs is fast enough to maintain the energy supply.
So let’s go back to this fat burning zone. On the treadmill or elliptical, one of the options for preset workouts is a fat burning one where you workout for about 30 minutes at a relatively low intensity. In theory, the machine isn’t lying to you. You are indeed burning “more” fat at this low intensity- you are burning a higher percentage of “fat” because there is not a high energy demand- however you are burning less calories overall. So let’s say this is some kind of miracle machine where you are burning 90% fat at this fat burning setting. BUT you are going very slowly so you are only burning 4 calories a minute. After a half hour, you have burned (30 minutes x 4cals a minute) 108 calories. That seems not bad…Now 90% of those calories were fat (150 x .90), so you just burned 97 fat calories. Yay!
But wait, let’s say now you decide to go at your own intensity, a much harder intensity where you are burning 10 calories a minute and you go for the same 30 minutes (30 *10= 300 cals). You were going faster so you are burning more carbs and less fat, maybe only 40% fat (300*.40), but wait, even at only 40%, you’ve burned 120 “fat” calories. You burned more fat calories than in the “fat burning” zone.
See, my friends, it might sound nice to burn all those fat calories away, but at the end of the day it comes down to total calories. Going at a higher intensity burns MORE total calories, and therefore more fat calories than the low intensity. So if you really want a good workout, go for high intensity.
Moreover, studies have shown high intensity interval training (HIIT) to be the best type of exercise for weight loss. This type of exercise is composed of interval style workouts where you do 1 minute of high intensity work and 1 minute of low (or rest). I did a study at UNC where we saw significant changes in weight and fat mass after only 3 weeks of 3 days a week, 20 minutes of 1min high/1min rest cycle exercise. That’s 60 minutes a week!
Don’t get me wrong, I’m not saying to only go to the gym for an hour a week. I AM saying that if you are in a time crunch and have 30 minutes to get your calorie burn on, turn up that resistance and do some intervals.
This post has focused mainly on calories and efficiency, but there is plenty of research available showing how the physiological and health benefits of high intensity workouts far outweigh those of low intensity workouts. Placing that kind of workload on your heart and lungs causes physiological improvements to occur. Your body will adapt to become more efficient at the workloads you are imposing on it. If you ask more, it will rise to the occasion. If you ask nothing, well, don’t expect much.
There is a place and a time for some long distance, long duration workouts depending on your goals, but if your goal is weight loss, high intensity interval training has been shown time and time again to be the most time efficient weight-loss exercise regimen. So swap out that slow motion, kindle watching treadmill time for some kick your butt intervals, and see what happens. It will revolutionize your workouts and your results.