Meal timing and intermittent fasting

meal timing and intermittent fasting

We often talk about what we should and shouldn’t eat.  But in addition to the effects of what we eat on our health, when we eat has a major influence too. A team of researchers from Germany set out to find out more about the impact of meal timing on ageing and metabolic health. As we know by now, metabolic health and blood sugar regulation directly impacts the immune system, so we should be all ears for this topic.


The German researchers found that disruption of the genetic clock, in other words meal timing, leads to dysfunction in the metabolism. And this metabolic dysfunction in turn leads to development of type 2 diabetes, obesity and associated metabolic diseases.


In contrast, living in sync with our environment and our natural needs coordinates efficient metabolic processes. Efficient metabolic processes lead to optimal health and not to obesity and associated health risks.


Since we generally stay awake longer than our great-great-grandparents did prior to electrical lights and screens to entertain them, we have also developed the habit of spending more hours a day eating. What researchers are finding is that our day-night rhythm has shifted to a later part of the day and with that, we eat more hours than we probably should in a 24 hour cycle. This habit is bad for our metabolism, our weight and our immune systems.


The German researchers found that some people were eating for up to 15 hours every day. This in turn negatively impacts the peripheral clock, which is a timekeeper we have in our bodies outside of our brains.  Feeding is one of the peripheral clock’s most important Zeitgeber.


You see great health benefits if feeding time is reduced to 8-12 hours in the 24 hour cycle.


Intermittent fasting, eating for only a part of the day, has become popular and is effective in reducing inflammation and regulating weight for many. However, sometimes our circadian rhythm is forgotten when choosing these feeding hours. I have dealt with many people struggling with their metabolisms despite intermittent fasting, because they eat too late in the day.


The researchers showed that eating the same calories in the morning produced a much better metabolic effect than exactly the same calories in the evening. The same meal in the evening might make you fat or unhealthy whereas in the morning, it might just give you useful energy without adding weight gain or metabolic problems.


Having food in the morning agrees with our natural circadian rhythm. We wake up with a need for action in the morning—even if we don’t feel like we do. Our background metabolic rhythm is present in the form of action-and-motivation hormones and the metabolic efficiency to match it and make the energy we need.


Later in the day things slow down. It is then time to rest and regenerate. Late night is not the time to overeat and drink. Excess calories at night do not provide efficient energy, rather those calories end up being stored as fat. At the same time, your digestive system and liver would really enjoy some clean-up and rest time during the night. It is not programmed to be busy with digestion and management of freshly produced metabolic waste products at night. Your built-in clean-up system needs the night time to deal with everything produced during the day already.


In other words, intermittent fasting—eating for only 8-12 hours of the day—is a great idea for more efficient metabolism, weight loss, lowered inflammation and better immune system function. However, choose the hours wisely. Let them agree with your natural circadian rhythm.  In the words of Maimonides (1135-1204), “Eat breakfast like a king, lunch like a prince and dinner like a pauper.”


As we grow older, there is a shift in our biological clock where the peripheral clock dependent on feeding time as a Zeitgeber determines more our day-night rhythm than the central clock, seated in the brain, with light as its Zeitgeber. Natural light remains important and has many other benefits, but it is good to remember to pay attention to when we eat and when we fast.


People in the blue zones, which are areas in the world were people are known for their longevity, apply the principle of an early and small dinner. If they have wine, they have it with their food in the late afternoon, early evening. And then no more calories.


Take a tip from the blue zones. Have your dinner early if you can and stop your calorie intake after dinner. No more calories after dinner means not having alcohol, which contains plenty of calories and can interfere with your blood sugar and your biological clock. What works well after dinner is herbal tea (without honey), water, water with a slice of lemon, or on a hot day, have some sparkling water with ice and lemon. For more ideas of sugar- and alcohol-free drinks, have a look at the resources on my website.


In short, reduce your eating hours during the day. Aim to, as rule, fast at least 12-14 hours every night. That means, you should have an early dinner after which you have no calorie containing food or drinks.  Then 12-14 hours later you have a good breakfast.


There are some who see faster results on a 16 hour fasting time, meaning you eat only for 8 hours during the day. If you do consider doing this, you should however keep in mind that breakfast is still your most important meal of the day.  And think about whether you see the habit as sustainable.  I find the 12-14 hours fast and 10-12 hour eating window is generally more realistic to maintain. You do see great results as long as what you eat is still top quality and blood sugar stabilising foods. Remember it is important that your dinner is small.


If you can adopt the habit of fasting 12-14 hours a day long term, with maybe a cheat night once or twice a week depending on social and other events, you are doing yourself a great favour.  You will enjoy the potential benefits of better blood sugar control, lower inflammation, improved detoxification, more energy, more mental clarity and a much happier immune system.

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