Chronobiology and Obesity: The Orchestra Out of Tune

Marta Garaulet; Purificación Gómez-Abellán; Juan Antonio Madrid

Disclosures

Clin Lipidology. 2010;5(2):181-188. 

In This Article

When the Orchestra is Out of Tune: Chronodisruption

When the orchestra is out of tune within our body, we talk about CD, a term that suggests that rhythms can become desynchronized and that this may have adverse health effects. This disruption can occur over days, seasons and years. CD has been defined as a relevant disturbance of the internal temporal order of physiological, biochemical and behavioral circadian rhythms.[19] It is also a breakdown of the normal phase relationship between the internal circadian rhythms and 24-h environmental cycles. CD can be assessed in physiological studies as a reduction in rhythm amplitude – sometimes as a total loss of the rhythmicity, other times it can be characterized by a delayed or advanced phase between different peripheral clocks and the SCN and also as phase inversion of circadian rhythms, as is found in night workers.[20] An internal desynchronization among different physiological variables is also considered to be CD. In our modern 24/7 society, CD can be the result of several conditions or chronodisrupters,[19] such as jet-lag, shift work, nocturnal light pollution, sleep deprivation or nocturnal eating, all of which are highly associated with different pathologies, including obesity.[21]

Chronodisruption & Obesity

Epidemiological studies have demonstrated a consistent association between shift work and obesity. In fact, Di Milia et al. performed a cross-sectional survey of shift and day workers (n = 346) to investigate the association between obesity, job-related factors and sleep duration.[22] The authors concluded that mean BMI was significantly higher in shift workers than in day workers.[22] Another important study performed in a working population of 27,485 people from the Västerbotten intervention program (VIP) was analyzed. Cross-sectional data, including blood sampling and questionnaires were collected in a health survey. The authors concluded that "obesity, high triglycerides, and low concentrations of HDL-C seem to cluster together more often in shift workers than in day workers, which might indicate an association between shift work and the metabolic syndrome".[20]

Other works have reported that subjects with nocturnal ingestions of food were 4.4-times more likely to be overweight or obese than patients who did not report nocturnal ingestions.[23]

With respect to sleep deprivation, clinical studies have demonstrated that women reporting less than or equal to 5 h of sleep weighed approximately 3.0 kg more than 7-h sleepers. Indeed, Van Cauter et al. recently exhibited that healthy individuals restricted to 4 h of sleep for six consecutive nights exhibit impaired glucose tolerance and reduced insulin responsiveness following a glucose challenge. This situation is rather important among children in which short sleep duration has been described as an independent risk factor for obesity.[24]

Different causes could explain the association between sleep loss and obesity.[25] Studies with adults have demonstrated associations between inadequate sleep and alterations in leptin and/or ghrelin indicative of increased appetite,[26,27] accompanied by increased intake of calories from snacks with higher carbohydrate content.[28] Moreover, short sleep duration could lead to weight gain and obesity by increasing the time available to eat and has also been theorized to decrease energy expenditure by increased fatigue, as well as changes in thermoregulation that could explain obesity, particularly in children. In adolescents with increasing age the associations become weaker, possibly owing to higher sleep requirements in children.[28]

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