AbstractBackgroundMeal pattern is a potential health determinant. Previously, mean values for properties of meal pattern, such as daily meal frequency, have been considered. Means, however, obscure variability between‐day (irregular or chaotic eating). This systematic review aimed to identify and critique published methods used to characterise between‐day variability in meal pattern, and to explore relationships between this and obesity, as well as associated health outcomes.MethodsUsing relevant databases, a systematic search was undertaken for studies with adults and children in which between‐day variability in meal pattern was measured, and related to body weight, metabolic syndrome components and cognitive function.ResultsIn 34 papers identified (28 observational and six intervention studies), between‐day variability in meal pattern was characterised by a variety of methods. These ranged from single questions about intake regularity to more complex methods quantifying the degree of variability. Assumptions were made, such as there being three main meals, resulting in dissociation from the “clock time” of eating. In 24 of the papers, between‐day variability in meal pattern was associated with negative weight and health outcomes including higher weight, reduced thermogenic response to meals and poorer academic achievement.ConclusionsBetween‐day variability in meal pattern is a promising research area that might inform low‐cost public health interventions. However, current methods of characterising between‐day variability tend to make assumptions and be inconsistent in the meal pattern properties considered. Well controlled dietary intervention studies are required to confirm causation.