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Zone Living

Breaking down the latest research on Anti-Inflammatory Nutrition
Written By: Dr. Barry Sears, Ph. D | Creator of the Zone Diet

Written by Lisa Zeigel
on February 06, 2015


Just when it appears that everyone is on the same page knowing about certain fitness myths being uncovered and proven to be just that – mythical - I get a question from someone who has either missed the latest research that exists or is just plain stubbornly holding onto old-school notions for no good reason. This is understandable. There is too much information now at our fingertips, and with so many contradictions abounding, it really is difficult to believe everything you read and much easier to hold onto what you have learned before, no matter how “old school” it is.


Thankfully when it comes to fitness, there are reliable resources that can be counted on to provide the latest, evidence-based guidelines and information. Below are a few of the most common misconceptions about fat-burning and exercise I come across as a fitness professional countered with proven best practices.



  • To burn fat, one must remain in a “fat-burning” cardio zone
  • You only start burning fat after 20 minutes of exercise
  • You must perform “high-intensity interval training” or “HIIT” exercise to burn fat


  • No matter what the intensity level of your activity, your body is always burning something. In general, lower-to-moderate levels of activity do burn a higher percentage of fat (along with stored carbohydrates a.k.a. glycogen). However, when the intensity level increases, a higher percentage of glycogen is utilized along with some fat. In addition, at this higher level, more calories overall are burned than at the lower-to-moderate ranges. With more calories being utilized, one is thus burning more calories from fat, even if the percentage of carbohydrates is greater. The key thing here is burning more calories, however.
  • In addition, there is no magic number time-wise as to when you start burning fat. As in the case mentioned above, the body starts burning both fat and stored glycogen the moment you start moving. The number 20 was randomly assigned in a study conducted many years ago, and once it was published, it somehow stuck in everyone’s minds. In another study conducted in 1995 at the University of Pittsburgh, two groups of subjects performed cardiovascular exercise, one 20-40 minutes in duration and the other in bouts of 10 minutes spread throughout each day for 140 days. The group performing the frequent, shorter sessions lost more weight and was able to stick with activity because it seemed more doable than to allot a bigger chunk of time all at once to exercising. Although it is difficult to say how much fat each subject burned, you can see that the overall calorie usage resulted in weight loss, which is usually the most important concern.
  • As for “high-intensity interval training” or “HIIT,” which is so popular now again, the higher the intensity, the more calories you burn. This modality offers many other benefits, such as increased aerobic capacity, improved blood-sugar control, and better vascular circulation, which is important for heart health. It takes less time to get the same (or even better) results than long bouts of say, running on a treadmill at a moderate pace. Most importantly, it may be more enjoyable than what some people view as a tedious task (i.e., running on said treadmill for 30 minutes or more). There is also the possibility of more variety with the many different options that can be utilized in HIIT, such as manipulating the high-low intervals (e.g. 50/50 hard/easy combinations such as 60 seconds/60 seconds, or “Tabata” intervals of 20 seconds hard/10 seconds rest). The drawback is that it is not advisable to practice this as a sole means of exercise – interspersing vigorous exercise along with moderate to achieve 150 minutes total activity time per week is a recommendation that the American College of Sports Medicine (ACSM) and Center for Disease Control (CDC) endorse. This will ensure a well-rounded activity program and reduce the chance of injuries. In addition, anyone just starting an activity program or people returning from an exercise hiatus will need to use caution and ideally incorporate this type of training into a moderate program slowly.

When all is said and done, fat-burning is a product of other factors besides exercise. Another necessary component involves calorie intake – ideally less than what you are expending in order to facilitate weight loss. It is also desirable to build or maintain muscle mass – done through the added component of resistance training because that is a major driver of metabolism. The CDC and ACSM offer research-proven guidelines for this, too, (at least two times per week for major muscle groups).


Marketing and promotions would have you believe that there are magic numbers when it comes to fat and weight loss in fitness. The good news is that with all the variations and combinations that are possible, exercise can be more fun, interesting and rewarding, increasing engagement and adherence to achieve shorter-term (weight loss) and longer-term goals (a lifetime of activity)!

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