Does Sleep Curtailment Stimulate Appetite, Motivation to Eat and Dietary Intake in Humans? A Narrative Synthesis of Evidence and Considerations for Future Studies.

Insufficient sleep has been increasingly recognised as a risk factor for obesity, yet the underlying mechanisms remain incompletely understood. Research suggests that sleep restriction promotes excessive dietary intake, and it is commonly assumed that this relationship can be explained by appetite dysregulation. Human appetite is multifaceted and includes homeostatic appetite regulation (governed by energy balance), hedonic responses to food and motivation to eat. However, these appetitive dimensions have rarely been considered together when understanding the links between sleep restriction and excessive dietary intake. Having employed a systematic literature search, this review synthesises evidence from human randomised, controlled trials within a comprehensive conceptual framework to critically examine the veracity of assumptions on whether sleep restriction heightens appetite sensations and, subsequently, increases dietary intake. This review demonstrates that the effects of sleep restriction on appetite and motivation to eat were inconsistent and often incongruent with observed changes in dietary intake. In many cases, higher energy intake following sleep restriction was not explained by corresponding changes in appetite or motivation to eat, challenging prevailing assumptions about causal pathways. We propose that these inconsistencies are likely driven, at least in part, by methodological limitations and the lack of an integrative framework that guides study design and interpretation. This review highlights that a structured framework that explicitly links sleep, appetite and dietary intake is imperative and should be used to identify key gaps and sources of discordance in the literature. We conclude by outlining recommendations to advance research in this area in the future.