Background and purposeNapping is a widespread practice worldwide and has in recent years been linked to increased abdominal adiposity. Lipase E orLIPEencodes the protein hormone-sensitive lipase (HSL), an enzyme that plays an important role in lipid mobilization and exhibits a circadian expression rhythm in human adipose tissue. We hypothesized that habitual napping may impact the circadian expression pattern ofLIPE, which in turn may attenuate lipid mobilization and induce abdominal fat accumulation.MethodsAbdominal adipose tissue explants from participants with obesity (n = 17) were cultured for a 24-h duration and analyzed every 4 h. Habitual nappers (n = 8) were selected to match non-nappers (n = 9) in age, sex, BMI, adiposity, and metabolic syndrome traits. CircadianLIPEexpression rhythmicity was analyzed using the cosinor method.ResultsAdipose tissue explants exhibited robust circadian rhythms inLIPEexpression in non-nappers. In contrast, nappers had a flattened rhythm.LIPEamplitude was decreased in nappers as compared with non-nappers (71% lower). The decrease in amplitude among nappers was related to the frequency of napping (times per week) where a lower rhythm amplitude was associated with a higher napping frequency (r = -0.80;P= 0.018). Confirmatory analyses in the activity ofLIPE’s protein (i.e., HSL) also showed a significant rhythm in non-nappers, whereas significance in the activity of HSL was lost among nappers.ConclusionOur results suggest that nappers display dysregulated circadianLIPEexpression as well as dysregulated circadian HSL activity, which may alter lipid mobilization and contribute to increased abdominal obesity in habitual nappers.