Powerlifting Bench Press

Effect of Intensity of Physical Activity on Body Fatness and Fat Distribution

Tremblay et al (1) examined observations  of 1366 women and 1257 men who participated in the 1981  Canada Fitness Survey.  Subjects were tested for  energy expenditure of leisure-time activities and  estimated VO₂ max.  Body fat was measured  using skinfolds and anthropometric measurements were also  made.  Subjects were divided into 4 subgroups based  upon the METS for their leisure time activities.

FINDINGS:  Subjects engaging in the  most intense forms of exercise had the lowest skinfolds  and waist-to-hip ratios.  These differences remained  statistically significant after the effect of total  energy expenditure of leisure-time activity on body fat  and fat distribution was removed by covariance analysis.   The waist-to-hip ratio also remained significantly  lower for individuals engaging in high-intensity exercise  after the effect of subcutaenous fat on fat distribution  was accounted for.

IMPLICATIONS:  A large body of  research exists showing that high-intensity exercise is  better for fat loss than low-intensity exercise.  This  study supports this.  The idea that one must train  in the "fat-burning zone" to maximize fat loss  is a myth.  70% of the energy supplied to the body  at rest is supplied by fat, but nobody gets lean by  sitting around all day.  What matters is the total  daily energy expenditure;  the predominant fuel  source during exercise has little significance in changes  in body composition.  Some research has demonstrated  that, although a high-intensity exercise session may not  utilize a large amount of fat during a training session,  the amount of fat that is utilized by the body during  recovery from a training session is significantly higher  than for a low-intensity exercise session.  Also,  one can examine the physiques of track sprinters, who  regulary engage in short, high-intensity exercise  sessions, and notice how lean they are.  When  compared to the physique of an individual who regulary  engages in low-intensity exercise in the mythical "fat-burning  zone" (such as Richard Simmons), a huge difference  becomes apparent.

To put it in layman's terms, high-intensity  exercise allows you to utilize more fat calories while  sitting on your duff, and thus you get leaner more  quickly and efficiently than with low-intensity exercise.   A combination of strength training to build lean  body mass and high-intensity interval training (such as  sprint-slow jog intervals on the track) is the best  method for fat loss and developing an impressive physique.   However, high-intensity interval training is very  psychologically and physically demanding and also carries  a higher risk of injury;  thus, low- and moderate-intensity  exercise is still the best choice for unmotivated  individuals or individuals contraindicated for high-intensity  exercise.

1.  Tremblay, A., J. Despres, C.  Leblanc, C.L. Craig, B. Ferris, T. Stephens, and C.  Bouchard.  Effect of intensity of physical activity  on body fatness and fat distribution.  Am. J.  Clin. Nutr.  51:153-7.  1990.