The Fast Diet: The secret of intermittent fasting � lose weight, stay healthy, live longer (4 page)

Krista has done a number of studies on ADF, and what surprised her is that, even when they are allowed
to, people don’t go crazy on their feed days. ‘I thought when I started running these trials that people would eat 175% the next day; they’d just fully compensate and wouldn’t lose any weight. But most people eat around 110%, just slightly over what they usually eat. I haven’t measured it yet, but I think it involves stomach size, how far that can expand out. Because eating almost twice the amount of food that you normally eat is actually pretty difficult. You can do it over time; people that are obese, their stomachs get bigger to accommodate, you know, 5000 calories a day. But just to do it right off is actually pretty difficult.’

In her earlier studies, subjects were asked to stick to a low-fat diet, but what Krista wanted to know was whether ADF would also work if her subjects were allowed to eat a typical American high-fat diet. So she asked 33 obese volunteers, most of them women, to go on ADF for eight weeks. Before starting, the volunteers were divided into two groups. One group was put on a low-fat diet, eating low-fat cheeses and dairies, very lean meats and a lot of fruit and vegetables. The other group was allowed to eat high-fat lasagnes, pizza, the sort of diet a typical American might consume. Americans consume somewhere between 35 and 45% fat in their diet.

As Krista explained, the results were unexpected. The researchers and volunteers had assumed that the people on the low-fat diet would lose more weight than those on the high-fat diet. But, if anything, it was the other
way around. The volunteers on the high-fat diet lost an average of 5.6kg, while those on the low-fat diet lost 4.2kg. They both lost about seven centimetres around their waists.

Krista thinks that the main reason this happened was compliance. The volunteers randomised to the high-fat diet were more likely to stick to it than those on the
low-fat
diet simply because they found it a lot more palatable. And it wasn’t just weight loss. Both groups saw impressive falls in low-density lipoprotein (LDL) cholesterol, the bad cholesterol, and in blood pressure. This meant that they had reduced their risk of cardiovascular disease, of having a heart attack or stroke.

Krista doesn’t want to encourage people to binge on rubbish. She would much rather that people on ADF ate healthily, increased their fruit and vegetable intake, and generally ate less. The trouble is, as she pointed out rather exasperatedly, doctors have been encouraging people to embrace a healthy lifestyle for decades, and not enough of us are doing it. She thinks dieticians should take into account what people actually do rather than what we would like them to do.

One other significant benefit to Intermittent Fasting is that you don’t seem to lose muscle, which you would on a normal calorie-restricted regime. Krista herself is not sure why that is and wants to do further research.

One of the problems with ADF, which is why I am not so keen on it, is that you have to do it every other day. In my experience this can be socially inconvenient as well as emotionally demanding. There is no pattern to your week and other people, friends and family, find it hard to keep track of when your fast and feed days are. Unlike Krista’s subjects, I was not particularly overweight to start with, so I also worried about losing too much weight too rapidly. That is why, having tried ADF for a short while, I decided to cut back to fasting two days a week.

I now have my own experience of this to fall back on (see page 60), together with the experiences of hundreds of others who have written to me over the last few months. But what trials have been done on two-day fasts in humans?

Well, Dr Michelle Harvie, a dietician based at the Genesis Breast Cancer Prevention Centre at the Wythenshawe Hospital in Manchester, has done a number of studies assessing the effects of a two-day fast on female volunteers. In a recent study, she divided 115 women into three groups. One group was asked to stick to a
1500-calorie
Mediterranean diet, and was also encouraged to avoid high-fat foods and alcohol.
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Another group was asked to eat normally five days a week, but to eat a
650-calorie
, low-carbohydrate diet on the other two days. A final group was asked to avoid carbohydrates for two days
a week, but was otherwise not calorie-restricted.

After three months, the women on the two-day diets had lost an average of 4kg, which was almost twice as much as the full-time dieters, who had lost an average of just 2.4kg. Insulin resistance had also improved significantly in the two-day diet groups (see more on insulin on page 54).

The focus of Michelle’s work is trying to reduce breast cancer risk through dietary interventions. Being obese and having high levels of insulin resistance are both risk factors. On the Genesis website (www.genesisuk.org), she points out that they have been studying Intermittent Fasting at the Genesis Breast Cancer Prevention Centre, University Hospital of South Manchester NHS Foundation Trust, for over six years and that their research has shown that cutting down on your calories for two days a week gives the same benefits, possibly more, than by going on a normal calorie-reduced diet. ‘To date, our research has concluded that intermittent diets appear to be a safe, viable, alternative approach to weight loss and maintaining a lower weight, in comparison to daily dieting.’

If you eat 500 or 600 calories two days a week and don’t significantly overcompensate during the rest of the week, then you will lose weight in a steady fashion.

But is there any evidence that Intermittent Fasting does more than that? I recently came across one particularly fascinating study suggesting that when you eat can be almost as important as what you eat.

In this study, scientists from the Salk Institute for Biological Studies took two groups of mice and fed them a high-fat diet.
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The mice got exactly the same amount of food to eat, the only difference being that one group of mice was allowed to eat whenever they wanted, nibbling away when they were in the mood, rather like we do, while the other group of mice had to eat their food in an eight-hour time period. This meant that there were 16 hours of the day in which they were, involuntarily, fasting.

After 100 days, there were some truly dramatic
differences
between the two groups of mice. The mice who nibbled away at their fatty food had developed high cholesterol, high blood glucose and had liver damage. The mice that had been forced to fast for 16 hours a day put on far less weight (28% less) and suffered much less liver damage, despite having eaten exactly the same amount and quality of food. They also had lower levels of chronic inflammation, which suggests they had reduced risk of a number of diseases, including heart disease, cancer, stroke and Alzheimer’s.

The Salk researchers’ explanation for this is that all the time you are eating your insulin levels are elevated and your body is stuck in fat-storing mode (see the discussion
of insulin on page 54). Only after a few hours of fasting is your body able to turn off the ‘fat storing’ and turn on the ‘fat burning’ mechanisms. So if you are a mouse and you are continually nibbling, your body will just continue making and storing fat, resulting in obesity and liver damage.

By now, I hope you are as convinced as I am that fasting offers multiple health benefits, as well as helping to achieve weight loss. I had been aware of some of these claims before I got really interested in fasting and, though initially sceptical, I was converted by the sheer weight of evidence.

But there was one area of study that was a complete surprise: research showing how fasting can improve mood and protect the brain from dementia and cognitive decline. This, for me, was something completely new, unexpected, and hugely exciting.

The brain, as Woody Allen once said, is my second favourite organ. I might even put it first, as without it nothing else would function. The human brain, around three pounds of pinkish greyish gunk with the consistency of tapioca, has been described as the most complex object in the known universe. It allows us to build, write poetry, dominate the planet and even understand ourselves,
something no other creature has succeeded in doing.

It is also an extremely efficient energy-saving machine, doing all that complicated thinking and making sure our bodies are functioning properly while using the same amount of energy as a 25-watt light bulb. The fact that our brains are normally so flexible and adaptable makes it even more tragic when they go wrong. I am aware that as I get older my memory has become more fallible. I’ve compensated by using a range of memory tricks I’ve picked up over the years, but even so I find myself occasionally struggling to remember names and dates. Far worse than this, however, is the fear that one day I may lose my mind entirely, perhaps developing some form of dementia. Obviously I want to preserve my brain in as good a shape as possible and for as long as possible. Fortunately fasting seems to offer significant protection.

The man I went to discuss my brain with was Professor Mark Mattson.

Mark Mattson, a professor of neuroscience at the National Institute on Aging, is one of the most revered scientists in his field: the study of the ageing brain. I find his work genuinely inspiring – suggesting, as it does, that fasting can help combat diseases like Alzheimer’s, dementia and memory loss.

Although I could have taken a taxi to his office, I chose to walk. I’m a fan of walking. It not only burns calories, it also improves the mood, and it may also help retain your memory. Normally as we get older our brain
shrinks, but one study found that in regular walkers the hippocampus, an area of the brain essential for memory, actually expanded.
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Regular walkers have brains that in MRI scans look, on average, two years younger than the brains of those who are sedentary.

Mark, who studies Alzheimer’s, lost his own father to dementia. He told me that although it didn’t directly motivate him to go into this particular line of research – when he started work on Alzheimer’s disease his father had not yet been diagnosed – but it did give him insight.

Alzheimer’s affects around 26 million people worldwide and the problem will grow as the population ages. New approaches are desperately needed because the tragedy of Alzheimer’s disease and other forms of dementia is that once you’re diagnosed it may be possible to delay, but not prevent, the inevitable deterioration. You are likely to get progressively worse to the point where you need constant care for many years. By the end you may not even recognise the faces of those you once loved.

Just as Valter Longo had, Mark took me off to see some mice. Like Valter’s mice, Mark’s mice are genetically engineered, But they have been modified to make them more vulnerable to Alzheimer’s. The mice I saw were in a maze, which they had to navigate in order to find
food. Some of the mice perform this task with relative ease; others get disorientated and confused. This task, and others like it, are designed to reveal signs that the mice are developing memory problems; a mouse that is struggling will quickly forget which arm of the maze it has already travelled down.

The genetically engineered Alzheimer’s mice will, if put on a normal diet, quickly develop dementia. By the time they are a year old, the equivalent of middle age in humans, they normally have obvious learning and memory problems. The animals put on an intermittent fast, something Mark prefers to call ‘intermittent energy restriction’, often go up to 20 months without any detectable signs of dementia.
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They only really start deteriorating towards the end of their lives. In humans that would be the equivalent of developing signs of Alzheimer’s at the age of 80 rather than at 50. I know which I would prefer.

Disturbingly, when these mice are put on a typical junk-food diet, they go downhill much earlier than even normally fed mice. ‘We put mice on a high-fat and
high-fructose
diet,’ Mark said, ‘and that has a dramatic effect; the animals have an earlier onset of the learning and memory problems, more accumulation of amyloid and more problems with finding their way in a maze test.’

In other words, junk food makes these mice fat and stupid.

One of the key changes that occur in the brains of
Mark’s fasting mice is increased production of a protein called brain-derived neurotrophic factor. BDNF has been shown to stimulate stem cells to turn into new nerve cells in the hippocampus. As I mentioned earlier, this is a part of the brain that is essential for normal learning and memory.

But why should the hippocampus grow in response to fasting? Mark points out that from an evolutionary perspective it makes sense. After all, the times when you need to be smart and on the ball are when there’s not a lot of food lying around. ‘If an animal is in an area where there’s limited food resources, it’s important that they are able to remember where food is, remember where hazards are, predators and so on. We think that people in the past who were able to respond to hunger with increased cognitive ability had a survival advantage.’

We don’t know for sure if humans grow new brain cells in response to fasting; to be absolutely certain researchers would need to put volunteers on an intermittent fast and then kill them, take their brains out and look for signs of new neural growth. It seems unlikely that many would volunteer for such a project. But what they are doing is a study where volunteers fast and then MRI scans are used to see if the size of their hippocampi changes over time.

As I mentioned above, these techniques have been used in humans to show that regular exercise, such as walking, increases the size of the hippocampus. Hopefully similar
studies will show that two days a week of Intermittent Fasting is good for learning and memory. On a purely anecdotal level, and using a sample size of one, it seems to work. Before starting the Fast Diet, I did a sophisticated memory test online. Two months in I repeated the test and my performance had, indeed, improved. If you are interested in doing something similar then I suggest you go to www.cognitivefun.net/test/2. Do let us know how you get on.