In RCTs, the growth of the study population could be compared with growth curves from standard populations such as the WHO Child Growth Standards.
However, the legitimacy of this strategy would all depend on the research
question being asked. For example, if the question relates to the suitability of
a particular novel ingredient, an RCT with a control population fed the same
formula but without the reference ingredient would be required. On the other
hand, formula modification aimed at matching the growth rate of breastfed
populations might cause growth in the formula- fed population that can be
compared to the WHO Child Growth Standards.