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1. The aim of the present study was to investigate the effects of a short (1 day) fast by testing biohumoral variables associated with the human circadian rhythm. 2. Fifteen clinically healthy male volunteers (32 +/- 8 years old) participated in the study. Subjects were fed a control diet for 7 days. The last day was a control day and the following 8th day was the fasting day. Each subject was asked to collect urine seven times over a 24 h period. Chemical and hormonal variables were measured in each fractionated urine specimen. The time- qualified urinary excretion rates were biometrically analysed using conventional and chronobiological methods. 3. During fasting, significant incremental changes were detected in the urinary excretion rates of potassium, aldosterone, 17-hydroxycorticosteroids and adrenaline and significant decremental changes were detected in the excretion rates of sodium, chloride, creatinine, urea nitrogen, uric acid, 17-ketosteroids, noradrenaline and dopamine. The circadian rhythmicity of the variables was well preserved and remained almost stable throughout the fasting phase. 4. Fasting affected the mean oscillatory levels and oscillatory amplitudes of variables, suggesting that nutrients may have played roles as tonic and phasic modulators on the mechanisms that physiologically regulate ircadian rhythmicity.

Objective Diabetic patients (DP) refer increased hunger sensation (HS) when hyperglycemic but not yet ketogenic. As HS shows a within-day (ultradian cyclicity) and intra-day (circadian cyclicity) repetitivity, its recursive pattern was investigated in patients with type 1 and type 2 diabetes mellitus (DM), in compensated and uncompensated metabolic stage. Method: HS was approached in its cyclic structure by means of spectral analysis (SA), and in its circadian rhythmicity by means of Single Cosinor analysis (SCA), applied to self-rated scores of HS given every 30 min to their HS (orexigram) by DP. Results: Exaggerated periprandial, interprandial, and/or nocturnal peaks of HS were seen in the orexigram of both the type I and type II DP. Specific alterations in HS periodogram were detected, structurally denoting a relative prevalence of the ultradian components along with the deamplification and loss of the circadian harmonics. Discussion: The increase of HS (hyperorexia) in nonketotic DM may be formally attributed to a mechanism of frequency multiplication and amplitude demodulation in the multifrequency bioperiodic structure which physiologically regulates the recursive pattern to the daily HS in human beings. © 1996 by John Wiley and Sons, Inc.