Michael Mosley “There’s something else I want to try out for myself. Over the last ten years, average dinner times have shifted much later, from 5.30pm until nearly 8pm. And some scientists believe that eating this late in the evening isn’t doing us any good at all and could be upsetting our circadian rhythm. So I’m going to do an experiment on myself to find out if that is true. And curiously, it starts first thing in the morning. OK, so here we have a nice old-fashioned English fry-up. It’s my first meal of the day and I’m going to have another meal exactly like it in 12 hours’ time.
On the face of it, it’s not the worst experiment I’ve ever done, except that in the intervening 12 hours I’m going to have an awful lot of blood taken out of me. After both my morning and evening meals, the levels of fat and sugar in my blood will be measured. Prolonged high levels of either are bad for you. And this test will show if the time of day I eat makes a difference.
Circadian Rhythms control our Digestion - Dr John Johnson
That was the first blood I’ve had taken since breakfast time and what should be happening is my levels of fat in my blood should be beginning to surge upwards. For the next 12 hours, it’s no food, but plenty of blood sampling. Exactly 12 hours later, I have exactly the same meal. But will it have exactly the same effect on my body at this time of night?
What the blood tests reveal is that when I ate in the morning, my blood sugar got back to normal within two hours. And the fat in my blood started to drop after about three hours.
But after exactly the same meal in the evening, my blood sugar stayed high for much longer. And the fat levels in my blood were still rising even four hours after eating. This is a quite startling result. Clearly, eating this late at night isn’t good for us. So what’s going on?
Well, it seems we have an internal body clock that makes us process food differently throughout the day. So, what’s the optimum cut-off point for meals?
There’s only one way to find out.
Circadian Rhythms
Here at Surrey University, they study circadian rhythms - what happens inside your body over the course of a day. I volunteered to go into an isolation chamber for 24 hours, I imagine it’s going to be like a desert island - except no view, no sunshine and no sea.
In fact, I’m going to have my body monitored in every possible way while I’m shut in the chamber. Now, I’m not actually looking forward to this, but it will be really interesting to see what happens.
Keeping me isolated from the outside world for a whole day and a night allows researchers to measure my own internal body clock’s natural rhythm. I don’t get any proper meals, just regular small snack to keep me going. And every hour for 24 hours, my blood is taken to measure levels of fat and sugar. This is not one of my best self experiments.
The idea is to try and understand what our bodies do naturally, so we can find out their rhythms and discover what time is best for us to eat.
As evening approached, the fat and sugar levels in my blood started to rise, even though I’d had no meal. and then fell again when it came to morning. This was tied to the levels of a hormone in my blood called melatonin, which tells us when to sleep. So when I had a fry-up in the evening, this was adding to a natural rise in my blood sugar and fat levels.
Dr John Johnson can explain why this happens.
Dr John Johnson “OK, so, if you like, our bodies have developed to be prepared for having food at a certain time of day and to be fasting at another time of day, geared towards taking nutrients from the blood, storing them away in your metabolic tissues and then at night, when you’re supposedly fasting, these metabolic stores then release energy into the blood, so that the tissues like your brain still have a good supply of energy.”
Michael Mosley “So your fat levels are rising in the early evening. If you reach into the fridge and you grab, you know, your bacon burger or whatever at 11 0’clock at night, is that a bad thing?”
Dr John Johnson “Generally, yes, because your body isn’t expecting you to be eating at that time of day. It’s expecting you to be fasting. And so what you find is that during that time, when people eat a meal, the spike of things like sugar and fat that you see in the blood after a meal is higher if you eat at night and that spike takes a bit longer to get down to background levels. So if you eat most of your calories certainly during the early part of the day and fewer calories in the late afternoon and evening, that will actually help your metabolism and potentially help you lose weight and maintain weight loss as well.”
Michael Mosley “So, there is good evidence that eating earlier can help us be healthier and maybe even lose weight.
Breakfast like a King, Lunch like a Prince, Dine like a Pauper
There’s an old adage - breakfast like a king, lunch like a prince, dine like a pauper. And it would certainly be a good idea to avoid that fatty, sugary food late at night when your body is least able to deal with it, at least according to your circadian rhythm.
If you have to have that fry-up, have it for breakfast.”
References
All of the above information came from the BBC series Trust Me, I’m a Doctor
