Recent research has highlighted fundamental changes in our knowledge about the workings of the circadian clock and how it orchestrates our sleep-wake cycles, when we eat and even the times our bodies metabolize nutrients. Getting a good night's sleep often comes down to two things--stress and diet.
There is a powerful link between circadian rhythms and metabolism and it is quickly becoming a new avenue for understanding disorders of both systems, including jet lag, sleep disorders, obesity and diabetes.
The timings of our meals effect our ability to lose weight so the integration of sleep rhythm data would help to build more effective personalised diet guides, experts have said.
During a conference on chrono-nutrition, circadian clocks and mealtimes at the Royal Society of Medicine, in London, earlier this month, Dr Jonathan Johnston, reader in chronobiology and integrative physiology at the University of Surrey, explained that our response to food depends on what time we eat that food.
As such, he said that chrononutrition - the practice of matching your food timings to your internal body clock aka circadian system - is an emerging and high-profile research area.
He explained that humans have many circadian clocks within their bodies and most of the main organs in the digestive system have their own clock. If our organs' clocks are not in sync with the 'master clock' - the brain - this can impact metabolism.
Andrew McHill led research published last year entitled "Later circadian timing of food intake is associated with increased body fat." The results showed that timing of food intake relative to melatonin onset was significantly associated with the percentage of body fat and body mass index whereas no relations were found between the clock hour of food intake, caloric amount, meal macronutrient composition, activity or exercise level, or sleep duration and either of these body composition measures. This showed that the consumption of food during the circadian evening and/or night, independent of the amount or content of food intake and activity level, plays an important role in body composition.
Dr Marta Garaulet, professor of physiology at the University of Murcia, Spain, has studied the research and conducted her own research into late night eating and its detrimental impact on weight management.
She said the research has shown that the ideal time for a person to eat their largest meal of the day is eight hours before dim-light melatonin onset. This essentially means that someone who tends to start to feel tired around 9pm should eat their biggest meal at 1pm.
Dr Suzana Almoosawi, research fellow at the brain performance and nutrition research centre, pointed out that people's circadian clocks change with age and therefore, diet and meal-timing advice should also be personalised to take into account the dieter's age.
"For example, usually younger people have a later circadian clock and older people have an earlier circadian clock and so I think eating plans should be targeted according to age and lifestyle."
Michelle Gibbs, dietitian and nutrition research consultant, pointed out that although it is extremely difficult to work out the precise time of someone's dim-light melatonin onset, this sort of knowledge could still successfully be utilised within personalised diet plans.
"It would take a huge amount of effort to measure a person's exact rhythm but you can ask them what time they start to feel tired, or what time they normally go to bed and they'll be able to give you a good idea of whether they are a morning lark or a night owl or somewhere in between."