high intensity interval training, weight loss

Low-intensity workouts lead to greater weight loss than high-intensity exercise that expends the same amount of overall energy, according to a new study carried out in Greece.

Fourteen healthy premenopausal untrained women were divided into two equal groups, which exercised on a treadmill at either 45% or 72% of VO2max four times a week for three months, expending 370 calories per exercise session and eating as normal.

All the participants lost weight, but the low-intensity group lost 1.4kg more than the high-intensity group – 3.3kg compared with 1.9kg. The researchers speculate that this may have been due to the different effects of the two intensities on their dietary and activity habits. For example, high-intensity exercise might stimulate appetite and/or encourage relaxation more effectively than the low-intensity variety.

Percentage body fat and fat mass decreased in all the participants, with no significant differences between the groups. Fat-free mass, by contrast, decreased in most members of the low-intensity group but increased in most of the high-intensity group.

This difference, say the researchers, ‘either suggests that high-intensity endurance exercise elicits some degree of muscle growth in untrained women, or simply reflects the fact that it was less effective in reducing body weight, or is due to a combination of the two.

Int J Sports Med 2006; 27:178-181