Acute effects of the very low carbohydrate diet on sleep indices

Discipline of Exercise and Sport Science, Faculty of Health Sciences, The University of Sydney, Sydney, New South Wales, Australia.
Nutritional Neuroscience (Impact Factor: 2.27). 09/2008; 11(4):146-54. DOI: 10.1179/147683008X301540
Source: PubMed


We compared the effect of short-term consumption of a very low carbohydrate (VLC) diet over 48 h to a control mixed diet on sleep indices in healthy, non-obese men.
This study employed a repeated-measure design where subjects were given isocaloric (2400 kcal) diets and matching evening test meals (4 h before usual bed-time), which were either mixed low-fat, high carbohydrate (15.5%, 12.5% and 72% of energy from protein, fat and carbohydrate, respectively) or VLC (38%, 61% and < 1% of energy from protein, fat and carbohydrate, respectively). Polysomnographic testing was performed on the familiarization and control night, 4 h after the first VLC test meal (acute phase) and 48 h (ketosis phase) following commencement of the VLC diet.
Fourteen healthy, non-obese men (aged 18-35 years; body mass index 23.4 +/- 1.9 kg/m(2)) who were good sleepers took part in the study.
Objective sleep was recorded using a computerized sleep system. Urine ketone level was monitored with reagent strips before the evening test meals and at bed-time on the control night, during the VLC acute and ketosis phases. Blood glucose level was measured with a glucometer before the evening test meal until 120 min following the meal. Hunger and fullness were assessed immediately after the meal until bed-time with Likert scales.
The proportion of rapid-eye movement (REM) sleep to total sleep time was significantly reduced at the VLC acute and VLC ketosis when compared to the control night (P = 0.006; n = 11 and P = 0.05; n = 14, respectively). The percentage of slow wave sleep (SWS) significantly increased for both the VLC acute (17.7 +/- 6.7) and ketosis (17.8 +/- 6.1) phases compared to control (13.9 +/- 6.3), P = 0.02 for both phases.
In healthy, good sleepers, the VLC diet over the short-term promotes increases in the percentage of SWS (deep sleep stage 4) and a reduction in the percentage of REM sleep ('dreaming' sleep) compared to the control mixed diet. The sleep changes may be linked to the metabolism of the fat content of the VLC diet.

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    • "Afaghi and colleagues [54, 55] conducted two studies investigating carbohydrate ingestion before sleep in healthy men. In the first study, high or low glycemic index (GI) meals were given 4 h or 1 h before sleep [54]. "
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    • ". While the total amount of carbohydrates may influence the architecture of sleep, it does not affect the duration. However, the evidence on whether carbohydrates positively impact sleep quality is not completely consistent, since consuming carbohydrate meals with high or low glycaemic loads seems not to affect any polysomnographically determined sleep index [55]. On the contrary, some components of the typical human diet, such as vitamin B12, improve alertness and concentration and reduce the daytime sleepiness phase [56]. "
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    • "In small children (n = 594), teenage girls (n = 126), and in a small study of 30 Greek women, a trend was observed toward longer sleep duration, with subjects consuming more energy from fat, whereas in other large studies with adolescents (n = 240) and adults (n = 459 and n = 2828), short sleep duration was correlated with increased fat intake [8,10–13,47,58]. Studies of high-fat, low-carbohydrate diets have not observed marked differences but only a remote trend on sleep duration, but also some influence on the relation of non-REM and REM sleep as described above [45] [49] [51]. "
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