In a recent blog series, I compared percent total body fat in college and professional football players. I want to continue to explore differences and similarities in college and professional football players in this blog. However, this time instead of percent total body fat, I want to compare visceral adipose tissue (VAT) between the two groups of football players. Some of you may remember a blog that I wrote on visceral adipose tissue or VAT. In that blog, I discussed how recent advances in dual X-ray absorptiometry (DXA) software now allow us to measure VAT. For those of you not familiar with VAT, it is fat that is located inside the abdominal cavity and is packed between the organs (stomach, liver, intestines, kidneys, etc.). VAT is important in overall health since an excess of VAT is an established marker for both cardiovascular and metabolic diseases (Kaess, et al., 2012; Katzmaryk et al., 2013). Although cardiovascular and metabolic health are important in athletes, we can also use VAT to monitor weight gain. Abdominal obesity has also been associated with increased risk of lower-body musculoskeletal injuries (Murphy et al., 2003; Nye et al., 2014), so athletes carrying large amounts of VAT may be at an increased risk for injury.
For this blog, I am going to use VAT data from a paper we recently published in the Journal of Strength and Conditioning Research (Bosch et al., 2019). This paper reported on VAT in over 467 NCAA Division 1 collegiate football players. I am going to compare these VAT values to a paper we also published in the Journal of Strength and Conditioning Research (Bosch et al., 2014) on VAT values in 342 professional football players. These two studies used the same model of dual X-ray absorptiometer (DXA) so it allows us to make comparisons between these two groups of football players without having to worry about differences in DXA scanners.
Visceral Adipose Tissue
In the figure below I have graphed VAT for both NFL (blue bars) and collegiate football players (red bars). One interesting trend for our athletes is that at all positions the level of VAT is greater in our professional vs. college football players. Given professional football players’ singular focus is on playing football this is somewhat surprising. However, you have to remember that professional football players are older than our college football players and we tend to accumulate VAT as we age (Whitaker et al., 2016). In addition, if you go back to our two blogs on percent total body fat, professional football players at each position on average tend to weigh more. We previously demonstrated that as professional football players gain weight there is a threshold where the increase in total body weight is disproportionately distributed as VAT (Bosch et al., 2014). We also found this threshold for a disproportionate gain in VAT with increasing weight in non-athlete adults (Bosch et al., 2015). The largest amount of VAT for both college and professional football players was found in the offensive linemen. This demonstrates the emphasis on total body weight that is placed on both college and professional football players that play this position. The professional offensive linemen had an average of 2.87 pounds of VAT while college offensive linemen had an average of 1.79 pounds of VAT. So the professional offensive linemen had over a pound more of VAT than the collegiate offensive linemen. After offensive linemen, the largest amount of VAT for both college and professional football players was found in the defensive linemen. This is not too surprising given that these individuals play the mirror defensive position to our offensive linemen. Professional defensive linemen had 1.98 pounds of VAT, while their college counterparts had 1.42 pounds of VAT. Defensive backs had the lowest amount of VAT with professional players having 0.66 pounds of VAT while college players had 0.45 pounds of VAT. Similar to what was found with the linemen positions, the second lowest-level of VAT was found in wide receivers, which is not too surprising since it is the mirror offensive position of the defensive backs. Professional wide receivers had 0.66 pounds of VAT while college wide receivers had 0.49 pounds of VAT.
What does it all mean?
Clearly, there is a wide range of VAT levels in both college and professional football players with the largest amount of VAT found in the lineman position. Although some coaches may want players in these positions to weigh a lot, the addition of this added weight may actually accumulate as VAT. This not only potentially increases an athlete’s risk for cardiovascular and metabolic diseases, but it also increases the potential for injury. Monitoring of VAT is a way to track weight gain to make sure that the additional weight gain is occurring in the right areas for an athlete. Finally, examining VAT levels is a way to monitor cardiovascular and metabolic risk factors for our athletes, both while they are playing sports and most certainly as they retire.
References:
Bosch TA, Burruss TP, Weir NL, Fielding KA, Engel BE, Weston TD, Dengel DR: Abdominal body composition difference in NFL football players. Journal of Strength and Conditioning Research 28(12):3313-3319, 2014.
Bosch TA, Steinberger J, Sinaiko AR, Moran A, Jacobs DR, Kelly AS, Dengel DR: Identification of sex-specific thresholds for accumulation of visceral adipose tissue in adults. Obesity 23:437-444, 2015.
Bosch TA, Carbuhn A, Stanforth PR, Oliver JM, Keller KA, Dengel DR: Body composition and bone mineral density of division 1 collegiate football players: a consortium of college athlete research study. Journal of Strength and Conditioning Research 33(5):1339-1346, 2019.
Dengel DR, Bosch TA, Burruss TP, Fielding KA, Engel BE, Weir NL, Weston TD: Body composition of National Football League players. Journal of Strength and Conditioning Research 28(1):1-6, 2014.
Kaess, BM, Pedley, A, Massaro, JM, Murabito, J, Hoffmann, U, Fox, CS. The ratio of visceral to subcutaneous fat, a metric of body fat distribution, is a unique correlate of cardiometabolic risk. Diabetologia 55: 2622–2630, 2012.
Katzmaryk, PT, Heymsfield, SB, Bouchard, C. Clinical utility of visceral adipose tissue for the identification of cardiometabolic risk in white and African American adults. American Journal of Clinical Nutrition 97: 480–486, 2013.
Murphy, DF, Connolly, DAJ, and Beynnon, BD. Risk factors for lower extremity injury: A review of the literature. British Journal of Sports Medicine 37: 13–29, 2003.
Nye, NS, Carnahan, DH, Jackson, JC, Covey, CJ, Zarzabal, LA, Chao, SY, Bockhorst, AD, and Crawford, PF. Abdominal circumference is superior to BMI in estimating musculoskeletal injury risk. Medicine & Science in Sports & Exercise 46(10) 1951-1959, 2014.
Whitaker KM, Choh AC, Lee M, Towne B, Czerwinski SA, Demerath EW. Sex differences in the rate of abdominal adipose accrual during adulthood: the Fels Longitudinal Study. International Journal of Obesity 40(8):1278-85, 2016.
About the Author: Donald Dengel, Ph.D., is a Professor in the School of Kinesiology at the University of Minnesota and is a co-founder of Dexalytics. He serves as the Director of the Laboratory of Integrative Human Physiology, which provides clinical vascular, metabolic, exercise and body composition testing for researchers across the University of Minnesota.