Let it be stated that weight loss is best achieved through diet. No amount of exercise can overcome the negative effects of an unbalanced and excessively high caloric diet. However, exercise can play an important and effective role in achieving decreases in body fat and weight loss. it’s also important to differentiate between overall weight and the context of what weight means regarding the balance of lean body mass and body fat. Although people often refer to weight loss in terms of pounds lost, most are more focused on pounds of body fat.
For many gym goers, they like to fall back on the concept that weight training is the best way to achieve decreases in body fat. Their belief comes from the fact that an increase in lean body mass, through gains in strength and muscle growth, will create higher metabolic demands throughout the day leading to greater calorie burn (Speakman & Selman, 2004). Although this is true, greater overall lean mass does require greater caloric burn to maintain, the difference isn’t significant for most and should not be used as a primary method for decreasing body fat.
The default activity for fat burning is moderate intensity aerobic exercise. By engaging in continuous aerobic exercise at a range of 40-75% of your max heart rate you will be in what many call the fat burning zone. This is the result of placing a moderate demand on the body that can mostly be covered by the burning of fatty acids in our aerobic energy pathway while pulling minimally from glucose in our anaerobic pathway (Romijn, Coyle, Sidossis, Zhang, & Wolfe, 1995). People looking to maximize the effects of aerobic exercise on fat burning will often perform this activity while in a fasted state. This will further decrease the body’s ability to pull energy from the burning of sugars and rely primarily on fats (Bergman & Brooks, 2017). The drawbacks to this method is the time requirement, often in the range of 40-60 minutes for 3-5 days a week, that for many find to be non-sustainable.
High Intensity Interval Training
There are those who argue that light aerobic training, although effective, is not the most efficient way to achieve decreases in body fat. High intensity interval training is a much shorter bout of exercise however requires the individual to exert themselves at a level much higher than the fat burning zone, often at heart rates of 85% of max or higher (Bayati, Farzad, Gharakhanlou, & Agha-Alinejad, 2011). The argument is that, although this method of exercise will not pull primarily from fat burning in oxidation due to higher exertion levels, it will burn a greater number of calories overall which will lead to greater decreases in body fat. Additionally, this form of exercise typically puts the individual is what is called an oxygen debt (EPOC) which can take an extended period of time after the cessation of exercise to recover (Hottenrott, Ludyga, & Schulze, 2012). During this extended recovery time the body is burning calories at a higher rate than they otherwise would again leading to greater overall calorie burn.
Bayati, M., Farzad, B., Gharakhanlou, R., & Agha-Alinejad, H. (2011). A practical model of low-volume high-intensity interval training induces performance and metabolic adaptations that resemble “all-out” interval training. Journal of Sports Science and Medicine, 10(September), 571–576.
Bergman, B. C., & Brooks, G. A. (2017). Respiratory gas-exchange ratios during graded exercise in fed and fasted trained and untrained men. Journal of Applied Physiology, 86(2), 479–487. https://doi.org/10.1152/jappl.19184.108.40.2069
Hottenrott, K., Ludyga, S., & Schulze, S. (2012). Effects of high intensity training and continuous endurance training on aerobic capacity and body composition in recreationally active runners. Journal of Sports Science and Medicine, 11, 483–488. Retrieved from http://web.b.ebscohost.com.libproxy.sdsu.edu/ehost/pdfviewer/pdfviewer?sid=f0b1d0d0-4829-498b-8424-beecd3bcec20@sessionmgr111&vid=20&hid=103
Romijn, J. A., Coyle, E. F., Sidossis, L. S., Zhang, X., & Wolfe, R. R. (1995). Relationship between fatty acid delivery and fatty acid oxidation during strenuous exercise. American Physiological Society, 1939–1945.
Speakman, J. R., & Selman, C. (2004). Physical activity and resting metabolic rate. Proceedings of the Nutrition Society, 62(03), 621–634. https://doi.org/10.1079/pns2003282