For years we’ve been advised to eat little and often, and never to skip breakfast. But now some scientists argue that stop-start eating, as our hunter-gatherer ancestors did, is better for us than ‘grazing’
COWS, SHEEP, goats — when it comes to diet, we have a lot to learn from the cloven-footed beast, it seems. “Grazing”, or eating little and often, has become something of a mantra among nutritional experts.
The theory is that several small meals a day helps to balance blood-sugar levels, reducing our desire to snack and to overeat. The reality is that once you start grazing, it’s often difficult to stop.
The other great dietary wisdom is that breakfast is the most important meal of the day — it will boost your brainpower and might even help you to stay trim. People who skip breakfast regularly are more likely to be overweight. If you must forgo a meal, it should be dinner.
Of course, few of us live as the experts recommend. We regularly skip breakfast or eat a large meal at the end of the day. Sometimes it’s easy to go for a whole day eating almost nothing, only to make up for it the next with a blowout.
All heresy in the current dietary lexicon. But could the experts have got it wrong? Recent research on rats suggests that such “bad” feeding patterns could actually be good for your heart and your brain — and might even help you to lose weight. The secret is to eat like a hunter-gatherer.
For several years Dr Mark Mattson, a neuroscientist at the National Institute on Ageing in Baltimore, has been fiddling with the feeding schedules of the rats in his laboratory; his findings suggest that the difference between being fat and at risk of heart disease, and slim with clear arteries, may lie less in what you eat than when.
Experts have long known that a sure way to increase the age-span of almost any animal is to put it on a semi-starvation diet. Rats and monkeys forced to subsist on 30 to 40 per cent of their normal intake have clearer arteries, lower levels of inflammation, better blood-sugar control and are less susceptible to damage of cells in the brain. But however healthy it may be, this brutal diet will never catch on — it’s just too unpleasant.
But Dr Mattson has discovered that restricting calories is not the only way to achieve these health benefits. Putting animals on an “intermittent feeding schedule” produces similar results. He found that when the animals were made to fast for a day and allowed to eat as much as they wanted the next, this warded off diabetes just as well as either exercise or constant semi-starvation.
In fact, not only were the animals as healthy, but they also lost weight, because over time they ate 30 to 40 per cent less food than a control group that was allowed to eat whenever it wanted to. The obvious question, then, is whether this approach would also work for people. Going without food one day and making up for it the next is not nearly as difficult to cope with as being permanently hungry.
“We have just finished a study with people who ate all their food in a two to four-hour period in the evening,” says Dr Mattson. The results have not been analysed fully but he is optimistic: “After the original study was published (in the Proceedings of the National Academy of Sciences) I was contacted by a number of people who had tried the day-on, day-off regimen and found that it allowed them to lose weight fairly easily.” One correspondent had even checked his blood and found some of the benefits reported in the rat study.
In an article in The Lancet last month, Dr Mattson raised doubts about some of our cherished notions about mealtimes. The evidence that breakfast is good for you is, he suggests, mixed; one study found that skipping breakfast was associated with smoking, drinking and being overweight, while another found that it actually improved insulin and glucose levels.
The popular notion that “grazing” is healthy is also less than clear-cut, says Dr Mattson, who points out that while some research has linked snacking to improved cholesterol levels, other studies have suggested that eating fewer meals a day is what makes the difference.
“Our basic metabolism was set up when we were hunter-gatherers,” he says. “The pattern would have been a mixture of feast and famine. Maybe we’d go several days without food, then splurge when a supply was found. We not only get much less exercise than our distant ancestors, but having a regular food supply as opposed to an intermittent one may prove to be almost as damaging.”
However, UK experts are not yet convinced that a person’s feeding pattern is that important. “There are so many things that can affect it, such as culture and habit,” says Dr James Stubbs, of the Rowett Research Institute in Aberdeen, which specialises in nutrition. “Even if intermittent feeding did promote weight-loss to begin with, the body would adapt and weight would soon go up again.”
What benefits there are come, he believes, simply because of the cast-iron law governing weight loss — the amount of calories coming in must be smaller than the amount of energy going out. “I’d be prepared to bet that any changes that show up in the studies are not to do with changes in schedule but because of changes in energy balance. Either the animals are eating less or exercising more.”
But perhaps there is another explanation for the beneficial effect of this new eating schedule. We know that chronic stress is bad for us; less well known is that a brief bit of stress — a shock such as a sudden change in temperature — can turn on your body’s repair mechanisms. This “healthy” stress is known as hormesis, and the best example of it is exercise. A hard workout generates dangerous free radicals and acids, as well as mildly damaging muscle tissue. But it also stimulates the body to begin a process of repair, mopping up the free radicals and mending muscle.
Professor Mario Kyriazis, medical adviser to the British Longevity Society, explains: “If you want to live a long and healthy life, quite the worst thing you can do is to avoid stress to either mind or body. Ageing is due to the loss of complexity in our system, and the way to boost complexity is to challenge the system. If you want to live long and healthily, don’t settle into routines.”
One striking effect of the stop-start diet on rats is that it increases the level of a brain chemical called brain-derived neurotrophic factor (BDNF), which protects neurons from degenerative diseases such as Alzheimer’s and Parkinson’s. This, says Dr Mattson, is another example of the hormetic benefits of on-off fasting.
As well as protecting against degenerative diseases, the stop-go diet might have a beneficial effect on depression, according to research from the Karolinska Institute in Stockholm. Kjell Fuxe, a professor of neuroscience, has found that higher levels of BDNF are linked to the feelgood brain chemical serotonin.
Research in this area is — curiously, given its importance — only just beginning, and Dr Mattson is careful to emphasise the point: “Until clear results are obtained in well-controlled studies,” he writes in The Lancet, “specific recommendations concerning meal frequency and health are inappropriate to make.” But he agrees that little harm is likely to come from experimenting with the stop-go diet to see whether it works for you.
http://www.timesonline.co.uk/articl...1707912,00.html
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