The main value of this article is the demonstration of an effect of a peptide hormone on estimated physical activity level as well as on eating behaviour. It also demonstrates the need to take an integrated approach to this type of research, assessing both intake and expenditure of energy. I found this article interesting because it reports the effects of the gut peptide oxyntomodulin on estimates of energy expenditure and feeding behaviour in free living subjects. There is increasing interest in the role of gut peptide hormones in the regulation of energy intake and expenditure, and thus, their potential role in the development and or treatment of obesity. Peptides such as GLP-1 (Flint et al., Int J Obes Relat Metab Disord 2001, 25:781-792 [ PMID:11439290 ]) and PYY (Batterham et al., New Engl J of Med 2003, 349:941-948 [ PMID:12954742 ]) have been shown to affect satiety and food intake, but none of the gut peptides have so far been shown to influence energy expenditure in humans. The study reports two exciting observations, that 3 days of repeated injections of oxyntomodulin reduces the amount of food eaten at an ad-libitum meal, and that the peptide also appears to increase total daily energy expenditure via an effect on the physical activity component. Whilst these observations are exciting, it must be noted that the treatment was only given for a total of 4 days, so chronic use may not lead to the maintenance of such effects. Also, the techniques for assessing total