The circadian rhythms of most night shift workers do not adapt fully to the imposed behavioural schedule, and this factor is considered to be responsible for many of the reported health problems. One way in which such disturbances might be mediated is through inappropriate hormonal and metabolic responses to meals, on the night shift. Twelve healthy subjects (four males and eight females) were studied on three occasions at the same clock time (1330 h), but at different body clock times, after consuming test meals, first in their normal environment, secondly after a forced 9 h phase advance (body clock time approximately 2230 h) and then again 2 days later in the normal environment. They were given a low-fat pre-meal at 0800 h, then a test meal at 1330 h with blood sampling for the following 9 h. Parameters measured included plasma glucose, non-esterified fatty acids (NEFAs), triacylglycerol (TAG), insulin, C-peptide, proinsulin and glucose-dependent insulinotropic polypeptide, and urinary 6-sulphatoxymelatonin. In contrast with a previous study with a high-fat pre-meal, postprandial glucose and insulin responses were not affected by the phase shift. However, basal plasma NEFAs were lower immediately after the phase shift (P < 0.05). Incremental (difference from basal) TAG responses were significantly higher (P < 0.05) immediately after the phase shift compared with before. Two-day post-phase shift responses showed partial reversion to baseline values. This study suggests that it takes at least 2 days to adapt to eating meals on a simulated night shift, and that the nutritional content of the pre-meals consumed can have a marked effect on postprandial responses during a simulated phase shift. Such findings may provide a partial explanation for the increased occurrence of cardiovascular disease reported in shift workers.

This article has been cited by other articles:

				R. Salgado-Delgado, M. Angeles-Castellanos, N. Saderi, R. M. Buijs, and C. Escobar Food Intake during the Normal Activity Phase Prevents Obesity and Circadian Desynchrony in a Rat Model of Night Work Endocrinology, March 1, 2010; 151(3): 1019 - 1029. [Abstract] [Full Text] [PDF]

				E. Maury, K. M. Ramsey, and J. Bass Circadian Rhythms and Metabolic Syndrome: From Experimental Genetics to Human Disease Circ. Res., February 19, 2010; 106(3): 447 - 462. [Abstract] [Full Text] [PDF]

				F. A. J. L. Scheer, M. F. Hilton, C. S. Mantzoros, and S. A. Shea From the Cover: Adverse metabolic and cardiovascular consequences of circadian misalignment PNAS, March 17, 2009; 106(11): 4453 - 4458. [Abstract] [Full Text] [PDF]

				M. J Prasai, J. T George, and E. M Scott Molecular clocks, type 2 diabetes and cardiovascular disease Diabetes and Vascular Disease Research, June 1, 2008; 5(2): 89 - 95. [Abstract] [PDF]

				S. Bhattacharyya, J. Luan, B. Challis, J. Keogh, C. Montague, J. Brennand, J. Morten, S. Lowenbeim, S. Jenkins, I. S. Farooqi, et al. Sequence variants in the melatonin-related receptor gene (GPR50) associate with circulating triglyceride and HDL levels J. Lipid Res., April 1, 2006; 47(4): 761 - 766. [Abstract] [Full Text] [PDF]

				E. B. Klerman Clinical Aspects of Human Circadian Rhythms J Biol Rhythms, August 1, 2005; 20(4): 375 - 386. [Abstract] [PDF]

				U. Holmback, A. Forslund, J. Forslund, L. Hambraeus, M. Lennernas, A. Lowden, M. Stridsberg, and T. Akerstedt Metabolic Responses to Nocturnal Eating in Men Are Affected by Sources of Dietary Energy J. Nutr., July 1, 2002; 132(7): 1892 - 1899. [Abstract] [Full Text] [PDF]

				M. J. Sopowski, S. M. Hampton, D. C. O. Ribeiro, L. Morgan, and J. Arendt Postprandial Triacylglycerol Responses in Simulated Night and Day Shift: Gender Differences J Biol Rhythms, June 1, 2001; 16(3): 272 - 276. [Abstract] [PDF]