Full text of Mark Mattson on Why Fasting Bolsters Brain Power – a TED Talk
Listen to the MP3 Audio here: Why fasting bolsters brain power Mark Mattson at TEDxJohnsHopkinsUniversity
Thanks, Brian. I’m at the National Institute on Aging. And as many of you know, as people are getting older and there have been advances in cancer research, cardiovascular disease research. Many people who would have died in their 50s and 60s from those diseases are living into the danger zone for Alzheimer’s and Parkinson’s diseases.
It’s projected that by 2050, the number of people with Alzheimer’s disease will triple from what it is today – 5 million today would be 15 million by 2050.
In my lab, we use a number of different animal models that are relevant to age-related neurodegenerative disorders. We have mice that accumulate amyloid in their brain as they get older and they have learning and memory problems. We have mice that have damage to dopamine producing neurons that control body movements, that’s miles of Parkinson’s disease and we also have miles of stroke which is again another major problem and cause of death.
Well it’s been known for a long time that one way to extend the life span of laboratory animals is simply to reduce their energy intake. And in rats and mice one can increase their life span by 30% or 40%.
We started looking at the effects of energy restriction on the brain in the context of age-related neurodegenerative disorders and found that we could slow down the, for example, abnormal accumulation about amyloid or the degeneration of dopamine neurons in the Alzheimer’s and Parkinson’s mile by reducing energy intake.
Now there’s a number of ways you can reduce energy intake. You can simply eat less at each meal or you can do what we call intermittent fasting. So reduce the frequency of the meals.
Effects of fasting on Brain
And what I’m going to tell you today is that fasting does good things for the brain. In the animals we have insight into a lot of the neurochemical changes that are occurring in the brain that we think explain why fasting is good for the brain.
But I’m going to start out and talk a little bit about anecdotal evidence that fasting is good for the brain and also an evolutionary perspective on why fasting might be good for the brain.
Okay. So everybody knows that in certain religions, people will fast periodically down through history. Many famous brain people — famous people with good brain have fasted regularly.
Up in the top here is a quote from Plato. He fasts for greater physical and mental efficiency.
“I fast for greater physical and mental efficiency.” – Plato
There’s some quotes there, including one from about 6,000 years ago from an Egyptian pyramid inscription that says;
“Humans live on one-quarter of what they eat; on the other three quarters lived their doctor”. – Egyptian pyramid encryption, 3800 BC
“Fasting is the greatest remedy – the physician within.” – Philippus Paracelsus (one of the three fathers of Western medicine)
“A little starvation can really do more for the average sick man than can the best medicines and the best doctors.” – Mark Twain
And in this country as you know, being overweight is a big problem. It’s not only a risk factor for cardiovascular disease and diabetes, certain cancers but emerging evidence suggests that it’s also a risk factor for age-related cognitive impairment and possibly Alzheimer’s disease.
In the lower right there is a reference to a book written over a hundred years ago by Upton Sinclair. Many of you may know Upton Sinclair is the author of The Jungle, a book on the meat-packing industry.
But he also wrote and published a book that you can find the full text online, it’s the Fasting Cure and in that book he interviews 250 people who had some ailment and went on a fast for various lengths of time and except in a handful of cases their health condition improved.
Okay. Before I focus on the brain, which will be the main part of my talk, I just want to point out that there’s evidence not just from animals but from humans that fasting is good for the body. It will reduce inflammation. It will reduce oxidative stress in organ systems throughout the body. And one thing that happens when you fast that does not happen when you eat three meals a day is that your energy metabolism shifts so that you start burning fats.
Every time you eat a meal, the energy goes into your liver and is stored in the form of glycogen. And that’s always tapped into first. And it takes about 10 to 12 hours before you deplete the glycogen stores in your liver.
Okay. So if you eat three meals a day, you never deplete the glycogen stores in your liver, although if you exercise you can. But once you deplete the glycogen stores in your liver, then you start burning fats and you produce what are called ketone bodies.
Now it turns out ketone bodies are very good for your brain and I’ll talk about that in a minute.
Now we’ve done a lot of work on animals in the ‘90s and between 15 and 20 years ago showing that intermittent fasting was good for the brain. Then we started collaborating with some investigators did some human studies looking at effects on the body, some that were shown in the last slide.
And then a producer at the BBC named Michael Mosley made a program on intermittent fasting that was aired on the BBC. It’s been aired on PBS. He wrote a book called the Fast Diet. And just in the last two years there has been a flurry of books on intermittent min fasting for health and it’s becoming what – I think what some people may think it’s a fad but hopefully it will — people can find some of these.
So what I mean by intermittent fasting or intermittent energy restriction, there is a lot of variations that are being and used on this – one, sort of harsh one is every other day only eat 500 calories. In our human studies we’re doing what’s called the 5:2 diet where two days a week you only eat 500 calories, the other five days you eat normally – eat healthy if you can.
This book called the Eight-Hour Diet. There’s evidence that if you restrict the time window that you eat each day to eight hours or less, it will have health benefits. Again that’s long enough to shift the energy metabolism.
Why does fasting bolster brainpower?
During development of your brain but also in the adult, neurons are generated from stem cells. They grow out their axons and dendrites, they form connections with each other’s synapses and communicate with each other.
During aging, many people, their brain ages successfully. They stay cognitively intact whereas unfortunately others develop diseases. We think the reason — the main take-home message of this talk is that fasting is a challenge to your brain and your brain responds to that challenge of not having food by activating adaptive stress response pathways that help your brain cope with stress and risk resist disease.
Does this make sense in evolutionary terms? When anything we talk about in biology, we have to always ask the question why is it that way? Why when we take animals and put them on an intermittent fasting diet, are their neurons protected in miles of Alzheimer’s and Parkinson’s disease? Why do they perform better when we test their learning and memory in maize? Well it if you’re hungry and haven’t found food you better figure out how to find food. You don’t want your brain to shut down if you’re hungry and in fact that’s what we find in the animals nerve cell circuits are more active.