A couple of studies...

I talked about this study back in 2006 when it was first completed. Well - it's finally been published. and since it's been about 16 months since I mentioned it - I thought I'd go over it again.

Trapp EG, Chisholm DJ, Freund J, Boutcher SH.

The effects of high-intensity intermittent exercise training on fat loss and fasting insulin levels of young women.

Int J Obes (Lond). 2008 Jan 15; [Epub ahead of print]

This study compared high intensity interval training to steady state aerobic exercise for a 15 week time period.

For the interval protocol, each subject performed 8 s of sprinting and 12 s recovery for a maximum of 60 repeats in a session (20 minutes). Subjects actually started with as little as 5 min in the beginning phase and gradually increased work time to a maximum of 20 min (by the 6 week point).

The steady state group performed 40 minutes of aerobic work at 60% VO2 max.

There was no difference in total energy expenditure (calories burned) during the exercise period between the two groups over the 15 week period, nor was there any difference in diet.

At the end of the study - both groups had improved their cardiovascular fitness (the interval training group by 23.8% and the steady state group by 19.3%)-- however -- the steady state group saw no loss in body fat (on average - the group gained 1lb), while the interval group had a significant reduction in total body mass, fat mass (11.2%), trunk fat and fasting plasma insulin levels.

Interestingly - the interval group decreased central abdominal fat by 9.5%, in contrast to the steady-state group, which had a 10.5% increase. Also - the interval training group showed an increase in lean mass over the course of the study - while the steady state group lost lean mass.

Once again - in a head to head comparison - interval training is superior as a fat loss tool over aerobic training.

The other studies I've been looking at recently are related:

Izumiya Y, Hopkins T, et al

Fast/Glycolytic muscle fiber growth reduces fat mass and improves metabolic parameters in obese mice.

Cell Metab. 2008 Feb;7(2):159-72.

Harrison BC, Leinwand LA.

Fighting fat with muscle: bulking up to slim down.

Cell Metab. 2008 Feb;7(2):97-8.

To briefly interpret these studies - fast twitch muscle hypertrophy seems to result in increased metabolism and reduced body fat - even when fed a high fat and high sucrose diet. The conclusion was:

"These findings indicate that interventions designed to increase skeletal muscle mass in at-risk human populations may prove to be critical weapons in the fight against obesity and obesity related comorbidities including diabetes, heart disease, stroke, hypertension, and cancer."

The study was performed in mice - but it will be interesting to see where these researchers go next. Maybe they'll start recommending weight training for fat loss ? :)

--
AC
www.alwyncosgrove.com
PS - for a complete fat loss program (including weight training and the latest methods of interval training) - check out Afterburn.