Optimal Fat Loss - Best Time, Intensity and Equipment: Medium Intensity Aerobic Exercise in the PM at 60% For Obese and >60% For Lean To get Shredded. Vibration Training Won't Help, Though.

Although I suppose that what I am about to tell you won't settle the everlasting debate on the effectiveness of early morning cardio training on an empty stomach (or even cardio training in general) for fat loss, you may nevertheless be interested to hear the results of a a study which has recently been published in the Journal of Human Sports & Exercise (Mohebbi. 2011).

Figure 1: Percentage of VO2Max for maximal (red) and minimal (green) fatty oxidation (main axis) and maximal fatty oxidation (secondary / right axis) absolute values in mg/min/fat free mass (data adapted from Mohebbi. 2011)

Mohebbi & Aziz recruited 12 normal-weight and 10 obese men for their study and measured maximal fat oxidation (MFO) in the course of a standardized treadmill incremental running exercise, where speed and increment were increased at 3 minute intervals. MFO was determined by VO2 / VCO2 measurements during the last 2 minutes of each exercise stage. With the participants performing the same exercise protocol twice, once in the AM (8-12h fasting) and once in the PM (5-6h fasting) the study design allowed to assess both, the effects of exercise time, as well as those of the exercise intensity on fatty acid oxidation in lean, as well as obese individuals. The main results were as follows:

fat oxidation rates and energy expenditure in both groups in the evening were higher than morning; there were no significant differences in MFO between obese and normal groups. Furthermore, the fat oxidation rate in low intensity exercise (<60% VO2max) was similar in obese and normal weight groups, but in high exercise intensities, in normal weight men were significantly higher than obese men.

Obviously, these results have practical implications in terms of exercise time and intensity which also depend on the training status / body composition of the individual. For "optimal" fat loss while training in a "fasted" (or at least not a postprandial state)...

• normal weight men optimally train in the PM at an exercise intensity >60% VO2max

• obese men optimally train in the PM at an exercise intensity of approximately 60% of their VO2Max 

The substitution of the good old treadmill for one of those fancy XXL-vibrators, which are used by more and more gym owners to rip off lazy... ah, I mean attract new clients, would turn out to be pretty useless, however. Published in the same journal is a paper by Cochrane (Cochrane. 2011) in which the author warns that in contrast to claims from the popular press, which say that "10 minutes of VbX [vibration exercise] is equivalent to one hour of traditional exercise", just hopping onto a giant vibrator although it may "increase whole and local oxygen uptake", even when executed ...

[...] with additional load, high vibration frequency and/or amplitude [...] cannot match the demands of conventional aerobic exercise. Therefore, caution is required when VbX programmes are solely used for the purpose of reducing body fat without considering dietary and aerobic conditioning guidelines.

Image 1: Not so innovative as you may have though:
"Vibration is life", advertisement dating back to 1910!
(Der Spiegel, 1/1999, p.145).

Fat or lean, lazy or not, you better get your asses off your vibrating couch and out into the park, because - guess what - you do not even need a treadmill to get in shape. Apart from some running shoes (some may argue running barefoot would be even better), nature already provided you with all the tools it takes to strip off the unaesthetic and oftentimes unhealthy fat-pads and get your six-packs summer-ready. You're still reading? What are you waiting for? Go for it!

On a side note: Isn't it interesting that the results of this study suggest that higher intensities become more and more effective, the leaner / fitter you get? Well, guess why most studies on obese people showed benefits of light intensity steady state cardio, while more recent studies on fit people or even athletes suggest that high intensity interval training (HIIT) is far superior to "recompose" your body.