"Exercise Does Not Burn Body Fat," says every scientist ever.

This is a paper I wrote while pursuing my personal trainer certification. When I started writing the paper, my goal was to come up with a list of exercises that were conclusively linked, in high quality scientific studies, to effective and efficient fat loss so that when I started working with clients I would have evidence behind my exercise recommendations.

What I found was baffling and upsetting.

p.s. I got full points on the paper and the professor, a PhD, began conducting his own research to see if what I found was true. 




Exercising To Lose Weight:
Which forms of physical activity have been linked to the effective and efficient burning of body fat?


Introduction

Loss of excess body fat is frequently confused with the more general term “weight loss.” Because weight loss includes water weight, lean muscle, and other bodily components, I used as research only documents and sources capable of differentiating between fat and weight. There are many sources of information regarding weight loss, but comparatively few credible sources on fat loss.


Physical Activity and Fat Loss

In 2008, the Physical Activity Guidelines Advisory Committee issued its report to the Secretary of Health and Human Resources. The committee had been asked to “review existing scientific literature to identify where there is sufficient evidence to develop a comprehensive set of specific physical activity recommendations,” and after almost a year, they turned in a nearly 700-page report.[1] When attempting to discern which exercises have effective and efficient results specifically in regards to burning excess body fat, this report seemed to be a logical starting point.

In this report, “Part G. Section 4: Energy Balance” contains the results of the analysis of 126 studies related to exercise and fat loss determined to have been conducted with sufficiently high standards. On page 264 the report reads in part, “However, in many weight loss studies, the proportion of the caloric deficit due to physical activity is only a small fraction of the overall caloric deficit, and consequently, the contribution that physical activity makes to weight loss is relatively small. This must be remembered as we address the role of physical activity alone on weight-related issues.”

And then on page 269 the committee reports, “The magnitude of weight loss due to physical activity is additive to caloric restriction, but physical activity is generally insufficient by itself to bring about clinically significant weight loss (in the long term).”

And then, regarding abdominal fat, on page 273 the report reads: “although physical activity is commonly prescribed to reduce overall obesity, the influence of exercise-induced weight loss on abdominal adiposity is not clear.”

Similar comments continue throughout the report’s pages. When these findings were condensed and released for public consumption under the title Physical Activity Guidelines for Americans,[2] in Chapter 2, under the heading “The Health Benefits of Physical Activity,” there are fifteen conclusions listed as being found with “Strong Evidence.” The only link between physical activity and burning body fat was written as this bullet point: “Weight loss, particularly when combined with reduced calorie intake.”

The implication is clear: A large committee consisting of industry leaders, scientists, and educators reviewed 126 clinical, peer-reviewed studies on physical activity and concluded, for our purposes, three things: (1) there are numerous benefits to be gained through physical activity, (2) permanent diet change is a significantly more effective way to burn fat, and (3) while there does appear to be some connection between physical activity and fat loss, no credible scientific study exists that specifically links exercise of any kind to the efficient and effective burning of excess body fat.

The U.S. government is not the only organization unwilling to connect specific exercises to burning body fat due to a lack of evidence. When describing the risks of physical inactivity, Johns Hopkins Medicine does not include fat gain as one of the clearly established factors.[3] In fact, although while on the website they state that obese individuals can reduce their risk for various diseases by being active, Johns Hopkins Medicine does not claim or imply that physical inactivity plays any role in the accumulation of excess body fat. Their focus is also on diet.

If this is true—if an individual gains excess body fat primarily because of diet and not due to a combination of diet and a sedentary lifestyle—we must ask ourselves: What role does exercise play in the elimination of excess body fat? We will examine the evidence surrounding strength training and aerobic exercise independent of dietary changes.


Strength Training

Strength training is a type of exercise that utilizes resistance (often weights) to increase strength and/or anaerobic endurance. Engaging in strength training to build lean (skeletal) muscle tissue is often recommended to individuals who wish to burn body fat. Are strength training exercises effective and efficient at burning body fat?

The Centers for Disease Control and Prevention, when talking about strength training, notes that “individuals who have more muscle mass have a higher metabolic rate … which is enormously helpful for fat loss and long-term weight control.”[4]

There are two thoughts behind this strategy: (1) If a body increases the amount of lean muscle mass, then metabolism will also increase and then passively burn additional stored body fat, even while at rest, and (2) simply engaging in strength training exercise will burn stored body fat.

The first point, while strictly speaking is accurate, is also misleading. The resting metabolic rate (RMR) of one pound of body fat is about 2 calories a day, while the RMR of lean muscle is about 5 calories a day.[5] In context, because other organs have a significantly higher rate (for example, kidneys have a RMR of about 200 calories per pound per day[6]), the difference in calories burned between fat and muscle is relatively low. This does not mean that adding muscle tissue should not be a goal; indeed it should. Or that adding additional muscle will not result in burning more calories; indeed it will. But the strategy of burning a clinically significant amount of body fat passively simply by building additional lean muscle is inefficient.

Regarding the second point, is strength training an efficient method of burning body fat through calories burned by exercise alone? The Centers for Disease Control and Prevention do not seem to think so. They state, “The important thing about strength training is the change in body composition. You will gain muscle and most likely decrease body weight even if your body fat stays the same.”[7]

This sentiment is echoed by other organizations, such as the American College of Sports Medicine, which lists the benefits of strength training as muscle, bone, and hormone health, but not fat loss.[8]

In other words, while strength training has many health benefits, it may or may not result in significant fat loss, thus making strength training an inefficient activity if your primary goal is to burn body fat.


Aerobic Exercise

Aerobic or cardio exercises are physical activities that strengthen the heart, lungs, and other parts of the cardiovascular system. Engaging in aerobic exercise is often recommended to individuals who wish to burn body fat. Are aerobic exercises effective and efficient at burning stored body fat?

According to a paper written by researchers at the St. Paul-Ramsey Medical Center, in regards to moderate-intensity aerobic exercises, the answer is no. The researchers list many results related to aerobic exercise, including managing certain medical conditions, positive mental benefits, and the reduction in risk for coronary heart disease. Regarding the effects of cardiovascular exercise on the burning of stored body fat, the paper does not list any conclusive evidence; it merely states that “aerobic exercise can also be an important adjunct to a weight-loss program.”[9]

For a paper consisting of concrete medical findings, the vagueness of this statement implies that the researchers have not found the same conclusive links between aerobic exercise and loss of body fat that they found between aerobic exercise and a reduction in cardiovascular diseases.

Because of this, we can infer that, while there is likely some benefit, moderately intensive aerobic exercise has not been proven in a clinical setting to be effective at burning excess body fat.

Studies indicate, however, that aerobic exercises at a moderate-intensity level affect the body differently than similar exercises undertaken at a high-intensity level. In his original 1996 study, Dr. Tabata did a 6-week experiment comparing the effects of high-intensity interval training with those of more traditional moderate-intensity training.[10] His findings were so significant that an exercise routine called “Tabata intervals” based on his laboratory work has been increasing in popularity ever since. In his study, Dr. Tabata found a number of benefits associated with high-intensity training as compared with moderate-intensity training; however, he did not find any difference in regards to the effectiveness or efficiency of body fat loss.

Another study, this one conducted at the University of Notre Dame in New South Wales Australia, confirmed Dr. Tabata's findings by identifying many health and wellness benefits associated with high-intensity training, but the second study was also unable to link these exercises directly to the loss of body fat.[11]


In Conclusion

There is ample evidence from a variety of sources to arrive at two conclusions in regards to the effect of exercise on the burning of excess body fat. First, dietary changes, although not a part of this paper, are found to be significantly more effective and efficient at burning body fat than any documented exercise routine.

Second, many highly respected institutions will not list fat loss as a result of exercise, or if they do, will list it in conjunction with dietary changes.

Based on this evidence, it does not appear to be accurate to claim that any form of exercise is significantly effective or efficient at burning excess body fat.








References
[1] Physical Activity Guidelines Advisory Committee. Physical Activity Guidelines Advisory Committee Report, 2008. Washington, DC: U.S. Department of Health and Human Services, 2008. Available at http://www.health.gov/paguidelines/Report/.
[2] 2008 Physical Activity Guidelines for Americans. Washington, DC: U.S. Department of Health and Human Services, 2008. Available at http://www.health.gov/paguidelines/guidelines/.
[3] Johns Hopkins Medicine. Risks of Physical Inactivity: What health risks are associated with physical inactivity? Baltimore, MD: Author. Available at http://www.hopkinsmedicine.org/healthlibrary/conditions/cardiovascular_diseases/risks_of_physical_inactivity_85,P00218/.
[4] Centers for Disease Control and Prevention. Physical Activity: Why strength training? Atlanta, GA: Author. Last reviewed February 24, 2011. Available at http://www.cdc.gov/physicalactivity/growingstronger/why/.
[5] Wolfe RR. The underappreciated role of muscle in health and disease. Am J Clin Nutr. 2006 Sep;84(3):475-82. Available at http://www.ncbi.nlm.nih.gov/pubmed/16960159.
[6] Ibid.
[7] Centers for Disease Control and Prevention. Physical Activity: Frequently Asked Questions. Atlanta, GA: Author. Last reviewed February 24, 2011. Available at http://www.cdc.gov/physicalactivity/growingstronger/faq/.
[8] American College of Sports Medicine. ACSM Current Comment: Strength Training for Bone, Muscle, and Hormones. Indianapolis, IN: Author. Available at http://www.acsm.org/docs/current-comments/strengthtrainingforbmh.pdf?sfvrsn=4.
[9] Mersy DJ. Health benefits of aerobic exercise. Postgrad Med. 1991 Jul;90(1):103-7, 110-2. Available at http://www.ncbi.nlm.nih.gov/pubmed/2062750
[10] Tabata I, Nishimura K, Kouzaki M, Hirai Y, Ogita F, Miyachi M, Yamamoto K. Effects of moderate-intensity endurance and high-intensity intermittent training on anaerobic capacity and VO2max. Med Sci Sports Exerc. 1996 Oct;28(10):1327-30. Available at http://www.ncbi.nlm.nih.gov/pubmed/8897392.
[11] Shiraev T, Barclay G. Evidence based exercise -- clinical benefits of high intensity interval training. Aust Fam Physician. 2012 Dec;41(12):960-2. Available at http://www.ncbi.nlm.nih.gov/pubmed/23210120.