For example, it assumes that the estimated size of the effect of (larger) size on consumption of food - typically measured in included studies of food products as the quantity of food or energy consumed from a single meal (or single course within a meal) - would produce the same size of effect on a person's energy intake over the course of a whole day.
It is therefore important to highlight that our discussion of potential policy actions that would be consistent with the evidence in this review concerning the effects of size on consumption of food (see Implications for practice, below) is necessarily tempered by consideration of where this body of evidence may be located on the 'absolute size continuum'.
We did not find evidence for an effect of individual unit size on consumption of tobacco, based on a meta-analysis of data collected from studies that investigated exposure to longer versus shorter cigarettes among adult smokers.
This result is set in the context of overall moderate quality evidence that the effect of exposure to larger size on consumption of food was present among both children (SMD 0.21, 95% CI 0.10 to 0.31 - moderate quality evidence - 1421 participants) and adults (SMD 0.46, 95% CI 0.40 to 0.52 - moderate quality evidence - 5182 participants) - see Figure 7 and Table 1.
Key findings and quality of evidence Effects of size on consumption: We found evidence that people consistently ate more food or drank more non-alcoholic drinks when offered larger-sized portions, packages or items of tableware than when offered smaller-sized versions.
Meta-regression analysis did not find evidence that the size of the effect of larger size on consumption was associated with the target of the manipulation (i.e. whether this was a portion, package, individual unit or tableware).
We found little evidence consistent with the proposal that the observed effects of size on consumption or selection may differ depending on whether it is the size of a portion, package, individual unit or item of tableware size that is altered.
Figure 8 comprises three bubble plots that show associations between study-level effect sizes (effect of larger size on consumption) and each of the three continuous variables identified as potential effect modifiers: FSA 'nutrient profile score'; FSA 'energy density score'; and participants' mean age.
The appropriate balance between the two areas of primary research we have highlighted will depend in part on the extent to which overall moderate quality evidence for a small to moderate effect of size on consumption is regarded as a sufficient basis for policy action to mitigate the undesirable consequences of such effects.
This review suggested that the effect of larger size on consumption may be robust to variation between interventions in terms of several of their key characteristics and those of their participants.
