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

two equal groups composed  of fourteen healthy premenopausal untrained women 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