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'Chrono-Nutrition' - how is our diet and metabolism influenced by the rhythms of our body's internal clock?

Liz Blamire

22nd September 2022

A controlled study in healthy people considered 'obese' on the BMI scale has shown that the timing of the largest meal of the day affects perceptions of appetite and hunger but not amount of calories burned.

Chrono-Nutrition is an area of study that suggests that our bodies process meals differently, dependent on the time of day. This is because our internal body clock or circadian rhythms, regulate most of our biological systems including our metabolism (the chemical reactions in the body's cells that change food into energy).

To investigate potential effects of the timing of the largest meal of the day, a randomised controlled trial, lasting 4 weeks and involving 31 'obese' participants, was carried out: Timing of daily calorie loading affects appetite and hunger responses without changes in energy metabolism in healthy subjects with obesity Half of the participants ate their largest meal in the morning at breakfast, whilst the remaining half ate their largest meal in the evening. All participants ate in a calories deficit (consuming less calories than you burn), with the aim of losing weight. Resulting weight loss (and therefore calories burned) was not significantly different between the two groups. However, self-reported feelings of satiety (feeling that you have eaten a sufficient amount/ fullness after a meal) was higher in the participants that had a large breakfast.

So what are the implications of this research?

These results suggest that loading calories in the morning does not change metabolism because big breakfast participants did not lose more weight than big dinner participants. However, because the big breakfast participants felt more satiated (full after meals), we can expect that they will be more likely to remain committed to the calorie deficit eating. If you are less hungry, you will eat less, if you feel more full, you will be happier!

There is a great summary of this research on The Conversation - Weight loss: the time of day you eat your biggest meal has little effect – new study

And an associated report on the BBC - Bigger breakfasts better for controlling appetite, study suggests

Liz Blamire

Liz is the current tutor2u subject lead for Health and Social Care. She is a former NHS midwife, who has worked in community, birth centre and acute hospital settings. Liz is an SSAT Accredited Lead Practitioner, who has taught Health and Social Care in FE and secondary schools, where she was a successful HOD. Liz is an experienced senior examiner and author.

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