Chrononutrition: when we eat matters

Posted on 23 June 2019

Chrononutrition: when we eat matters

“Stop throwing jargon at us, Dr Dil!” It’s not as bad as you think, honest. The term ‘chrononutrition’ simply links the roles of rhythm and nutrition, so essentially the timings of what you eat. It may sound obvious but our body is full of rhythms, overarched by the circadian rhythm which is around 24 hours, i.e. 1 day. Your body is constantly responding to how you eat not only in terms of hunger, satiety and nutrition but also with respect to hormones, epigenetics and the microbiome, all of which have cycles too.

It’s probably obvious to everyone that the timing of our eating matters. We get hungry and we eat; if we don’t eat we get hungry. And most of us are used to eating 3 meals a day and in many cases, plenty of snacks. So what do we know about chrononutrition? Well, the same meal eaten at different times of the day is metabolised differently. For example, triglycerides, i.e. fats, remain elevated at night and so we ought to plan our meal composition accordingly. For anyone looking to lose weight, the research shows that it can be done quicker if more of your calories are consumed earlier in the day. There is data that suggests eating within a restricted time window can also improve weight loss. In animals, this time-restricted feeding also leads to changes in genes associated with circadian rhythms in the liver and brain. So when we eat not only influences our metabolism but our genetics too. This is an example of an epigenetic phenomenon, whereby gene expression is influenced by environmental factors. The most alarming study showed that women eating later in the day exhibited metabolic changes that usually occur in obese women, such as reduced glucose metabolism and altered body temperature, when compared with earlier eaters. Broadly speaking, it seems that in the same way our sleep patterns should naturally correlate with when it is light and when it is dark, we are adapted to eat during the day.

The research on chrononutrition is all very interesting but all of the above is premised on a 3-meal day. I don’t know about you but I imagine a cave man back in the day would not have necessarily had a plentiful supply of food to eat 3 meals consistently all year round. Even if they had food, preserving it would not have been possible for most things. So that means our ancestors would most likely have gone through times of starvation and times of plentiful food. Our 3-meal day is merely a social construct. This is why so many people are interested in the idea of intermittent fasting or ‘IF’, which involves fasting in various regimes such as for 16 hours of the day or on alternate days. It matches up more closely to the conditions from which we evolved. Unfortunately there is less research for IF as yet but there is enough out there to suggest it could be really beneficial to reduce the effect of ageing and even reverse chronic diseases like diabetes.

So what can you take away from all of this about chrononutrition? A few things:

  1. Eat fewer calories in the evening, most easily done by reducing carbs at dinner
  2. Don’t eat too late at night; set yourself a rule like not eating past 8pm
  3. Avoid snacking to give your gut some down time
  4. If intermittent fasting or fewer meals seems to align with your health goals, research as much as you can and involve an experienced health professional to guide and monitor you. Be especially careful if you have any conditions like diabetes - we wouldn’t want to risk a hypo!

They may be simple but they can go a long way, even as far as altering your genetics!

Dr Dilraj Kalsi uses Lifestyle Medicine and Digital Health to empower patients to reverse disease via his online clinic Hippocrates Lounge. He is a Lecturer in Digital Health at the University of Warwick and publishes regularly on patient empowerment with colleagues from Oxford University. For all his latest health tips straight to your inbox, sign up here!

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