High Intensity Resistance Training Increases Fat Burning At Rest Even Without Dieting

Performing High-Intensity Interval Resistance Training (HIRT) can increase the amount of fat you burn when not exercising or dieting.  It has been known for ages that performing hypertrophy style (8-12 reps) or circuit training with short rest interval improves your body composition by increasing or maintaining your muscle mass whilst burning fat stores, the holy grail, however you may be better off increasing the intensity of your workout even further.
A recent study from Italy tested the acute effects of HIRT vs. traditional resistance training (TT) on resting energy expenditure and amount of fat burnt for 22 hours post-exercise.  Seventeen trained males carried out HIRT and TT protocols. The HIRT technique consists of using a weigh that the subjects could lift a maximum of 6 repetitions, 20 seconds rest, then as many as possible (usually 2/3 repetitions), 20 secs rest, then as many as possible again.  This counted as one set and the subjects performed two or three sets, with two to three minutes rest between sets.  The subject performed one leg exercise, one chest exercise and one back exercise for a total of 7 sets. The training session lasted approximately 32 minutes (including the warm up period).  The TT technique consisted of eight exercises of 4 sets of 8 – 12 repetitions with one/two minutes rest with a total amount of 32 sets.  This training session lasted approximately62 minutes (including the warm up period).

The researchers measured resting energy expenditure and respiratory ratio (which predicts energy source) for22 hours after the training session. They found that HIRT showed a greater significant increase energy burnt after the session and that more fat was used as an energy source.
This study suggests that shorter HIRT sessions may increase the amount of energy you burn afterwards and the amount of fat used as that energy source.
The shorter exercise time commitment may help to reduce one major barrier site to not being able to exercise, having enough time.

Reference:
Paoli et al (2012). High-Intensity Interval Resistance Training (HIRT) influences resting energy expenditure and respiratory ratio in non-dieting individuals. Journal of Translational Medicine.10:237