Background
Society has changed enormously in recent decades and this has had a strong impact on the
processes regulating circadian rhythms, in particular the sleep-wake and fasting-eating
cycles. The 'normalisation' of the environment, favoured by technological progress, has in
fact caused light pollution, noise pollution, excessive thermoregulation, continuous work
shifts and disordered eating, leading to an uncoordinated circadian cycle with consequences
on physical and mental balance. In humans, prolonged alterations of the biological clock have
been linked to cognitive disorders, premature ageing, and oncological and metabolic diseases
such as diabetes and obesity. Obesity, in particular, is a condition with innumerable
negative effects on human health.
In recent years, a new branch of nutritional research has aroused growing interest in the
scientific community: this is chrono-nutrition, which combines elements of nutritional
research with elements of chronobiology and studies the impact of eating times on health. The
first to use the term "chrono-dystrophy" as a chronic desynchronisation of circadian rhythms
were Erren and colleagues, who in their work reported how a loss of synchronisation between
environmental signals and physiological processes can lead to alterations in the
communication between the central nervous system and peripheral clocks and a change in the
subject's metabolism. Subsequently, numerous studies have evaluated the impact of the
thirteen dimensions of eating behaviour - timing, frequency and regularity - on health,
hypothesising a possible role of the individual circadian rhythm, or chronotype, on the risk
of developing overweight and/or obesity. Recent data have demonstrated a relationship between
a person's chronotype (morning or evening) and eating habits, as well as the importance of
adapting these habits to physiological rhythms. Furthermore, it has been suggested that
customising the caloric distribution of meals according to personal circadian rhythms may
influence body weight and be one of the strategies to control overweight and obesity. Indeed,
recent research has shown that calories ingested at different times of the day have different
effects on energy utilisation, leading to differential weight loss, even in the presence of
isocaloric quantities.
Despite the strong interest in this topic and the increasing number of observational studies
conducted, there is currently a lack of intervention studies evaluating whether a dietary
regimen can be used to control body weight. Evidence to date suggests that in order to
increase the effectiveness of low-calorie diets, it may be of great interest to consider not
only patients' daily energy expenditure but also their circadian preferences. Overall,
chrono-nutrition could mediate the effects between sleep, diet and urbanisation, but further
research is needed to elucidate the precise physiological and metabolic mechanisms underlying
this phenomenon, the importance of chronotype for metabolic health and its impact on public
health.
Objectives of the study
The objectives of the study are to compare the effects of a diet with a daily calorie
distribution adapted to the individual chronotype with a control diet with a conventional
daily calorie distribution. The primary outcome is weight change from baseline. Secondary
outcomes are changes in body mass index (BMI), percentage of fat mass, biochemical parameters
and gut microbiota profile.