We appreciate the comments of Dr Lappe on our longitudinal study of milk consumption and weight gain in adolescents.1 To clarify a point in her letter, our earlier (2004) study of sugar-added beverages and weight gain was a longitudinal study as well.2 The cross-sectional association she cited was from baseline data and not the major focus of that article, but it illustrates the risk in overinterpreting cross-sectional results. Children who were heavier at baseline drank less milk and more diet soda; we should not conclude from this that drinking more diet soda causes weight gain, nor that drinking less milk causes weight gain.
Berkey CS. Why Blame Milk?—Reply. Arch Pediatr Adolesc Med. 2005;159(12):1186-1188. doi:10.1001/archpedi.159.12.1188