Modulation of food consumption in healthy adults by exposure to coloured lighting

Abstract

The circadian rhythm (body clock) describes an endogenous (self-sustained) cycle that, amongst other cyclic functions, signals to the body when it is time to eat via the secretion of appetite stimulating and satiety hormones. Those suffering a misalignment of the circadian rhythm, such as dementia patients, may experience interruptions to their eating behavior, often resulting in malnutrition. The circadian rhythm is adjusted (entrained) to the local environment by external cues, or zeitgebers, which include natural daylight. There is some evidence that artificial white lighting can be used to mimic natural daylight in order to entrain the circadian rhythm to modulate normal sleeping patterns in those suffering from misalignment and in those who are not. However, little is known about any effects that coloured lighting might have on the circadian rhythm, or any potential to entrain the circadian rhythm to modulate food consumption. The present study investigated the effects of exposure to blue and yellow coloured lighting whilst eating on food consumption. Thirty non-obese participants (Age 26.8 (12.5)) years completed a repeated measures trial on three separate occasions, one day per week, over a period of three weeks. For each trial, participants consumed an ad libitum homogenous pasta meal until 'comfortably full and satisfied' for the duration of 30 minutes. Visual analogue scales were used to record appetite throughout. After checking for normality, one way ANOVA with repeated measures and Bonferroni post-hoc analysis revealed a significant increase in food consumption for the sample under yellow lighting compared to the white lighting control (P = 0.009), and very significant differences in food consumption for the sample between yellow and blue lighting (P = 0.002). However, 3*2 ANOVA identified a colour*sex interaction, with males consuming significantly more food under yellow compared to white (P = 0.002), but no significant increase or decrease under any coloured lighting condition in females. There was no effect of colour on appetite, hunger, or mood. There was no effect of sequence or restraint on food consumption. These novel findings suggest that exposure to yellow coloured lighting whilst eating can increase food consumption, most specifically in males. Further research is required to establish how coloured light-induced changes in food consumption occur, and to identify if there is an optimum shade of yellow and duration of pre-load exposure. These findings could be of particular interest in the context of patients suffering from malnutrition due to circadian misalignment, and the potential to develop new noninvasive treatments through lighting design and medical device development. I would like to thank the staff and students of Sheffield Hallam University for their significant contributions to this study, without which it would not have been possible. Particular thanks are extended to my research assistants, who ably assisted me in the laboratory, and to each of the thirty wonderful participants...