Between-day variability in meal pattern may be a novel but underexplored determinant of health. Studies exploring associations between diet and health often focus on the chemical composition of the diet, for example, the percentage of total energy from carbohydrate consumed over 24 hours.  Since the 50’s, and with a resurgence of interest more recently, the impact of the temporal pattern of intake has been considered potentially important with respect to health. Attempts have been made to characterise the temporal profile of intake both with respect to type and amount of food consumed.  Generic terms such as ‘eating incident’ pattern or more commonly, ‘meal pattern’ have been used. Such measures as ‘meal frequency’, ‘time of eating’, eating interval’ or ‘time when 50% of a dietary component has been consumed’ have been used to characterise the properties of an individual’s temporal ‘meal pattern’ profile.  Typically, these measures have been expressed as the mean or median of several days, (eg. mean daily meal frequency).  However, using a daily mean or median obscures any between- day variability (‘irregular’ or ‘chaotic’ eating) and may mask the potential impact of between-day variability in meal pattern on health.

Recently, the potential for an individual to have an ‘irregular’ meal pattern has increased.  This is due, in part, to greater availability of ready prepared meals, facilitating independence from established family mealtimes; greater availability of ‘fast-food’ outside the home; and greater variation in work shift patterns. Concurrently, obesity and associated detrimental health consequences have increased. Recent observational and intervention studies, exploring associations between ‘chaotic’ consumption patterns and health, have identified that this may be an underexplored, novel risk factor for obesity and its consequences, namely components of the metabolic syndrome and risk of cardiovascular disease.  Energy intake regulation, or energy expenditure, for example the thermogenic response to food, may be affected, potentially independently of the nutritional composition of the diet.  However, observational results are inconsistent, potentially because of differences in the measures used to describe consumption patterns, and methods used to obtain an indicator of between-day variability in pattern.  A limited number of intervention studies have been undertaken, and exhibit more consistency in outcome.

The purpose of this presentation is to summarise the existing literature describing observational and intervention studies considering between-day meal pattern variability, and associations with health. The challenges posed by differences in measures of between day variability will be described.  Possible mechanisms of action will be considered, with reference to chrononutrition and the potential for a ‘chaotic’ meal pattern to disrupt circadian entrainment.