Eating under observation: a systematic review and meta-analysis of the effect that heightened awareness of observation has on laboratory measured energy intake.

Background: Laboratory paradigms are commonly used to study human energy intake. However, the extent to which participants believe their eating behavior is being measured may affect energy intake and is a methodologic factor that has received little consideration.

Objective: Our main objective was to examine available evidence for the effect that heightened awareness of observation has on energy intake in a laboratory setting.

Design: We systematically reviewed laboratory studies that allowed for experimental examination of the effect that heightened awareness of observation has on energy intake. From these experimental studies we combined effect estimates using inverse variance meta-analysis, calculating the standardized mean difference (SMD) in energy intake between heightened-awareness and control conditions and qualitatively synthesized potential moderators of this effect.

Results: Nine studies, providing 22 comparisons, were eligible for inclusion. These studies largely sampled young women and examined the energy intake of energy-dense snack foods. Evidence indicated that heightened awareness of observation was associated with reduced energy intake when compared with the control condition (random-effects SMD: 0.45; 95% CI: 0.25, 0.66; P < 0.0001). We found little evidence that the type of experimental manipulation used to heighten awareness moderated the overall effect.

Conclusions: The available evidence to date suggests that heightened awareness of observation reduces energy intake in a laboratory setting. These findings suggest that laboratory studies should attempt to minimize the degree to which participants are aware that their eating behavior is being measured.