Fasting for your health’s sake never seemed smart to me. Why starve for a day or so in the interests of detoxing, for instance, when there’s no real evidence that it works? Then there’s those sinking blood sugar levels – a cause of grumpiness, energy dips and wavering concentration.
But what if short regular bursts of fasting could do us some good in other ways – by shoring up our defences against heart disease, diabetes or Alzheimer's? Fasting might carry the taint of fringe medicine but it’s also the subject of serious research, with some scientists suggesting it may reduce chronic disease, a theory stemming from studies that underfeeding leads to a longer life - at least if you’re a rat.
In the US, researchers at the National Institute on Ageing in Baltimore have found that restricting food - again in rats – is good for their brain cells. It helps boost levels of a substance called BDNF – short for brain-derived neurotrophic factor – thought to help protect human brains from Alzheimer’s disease. (Exercise may have the same effect too – but that’s another story).
Meanwhile at the University of Adelaide’s Discipline of Medicine, research scientist Leonie Heilbronn is trying to find out if fasting every other day can help reduce cardiovascular disease in humans. The story so far is that intermittent fasting, as it’s known, lowers levels of cholesterol and other blood fats called triglycerides. What Associate Professor Heilbronn wants to nail down is what causes this effect – is it the fasting itself or any weight loss resulting from it?
“Studies are showing that fasting has health benefits in humans, but we also need to find out if people can actually do it – some people can get very grumpy,” says Heilbronn who, as her own guinea pig in a previous study, tried fasting herself. While she coped, some found it challenging.
In her study, fasting means eating just one meal a day – an early breakfast before 8am. These fasting days alternate with days of eating normal meals. If this kind of food restriction seems extreme, it’s because we forget that three meals a day with snacks in between hasn’t exactly been the norm throughout human history, especially for our hunter gatherer ancestors.
“We’re more geared for feasting and famine,” says Heilbronn.
Nor was it unusual – and still isn’t in some communities –for people following religious calendars to fast or at least eat less at certain times of the year.
So could old fashioned fasting turn out to be an antidote to modern over eating?
It wouldn’t surprise Katherine Samaras, head of Diabetes and Obesity Clinical Studies at Sydney’s Garvin Institute of Medical Research.
“There’s evidence that people who follow seasonal fasting, such as that embedded in the older faiths, live longer - this is after controlling for other factors like alcohol consumption, smoking and other lifestyle factors,” she says.
Still, it’s early days with this research and we’re a long way off prescribing regular fasting for anyone for the sake of their heart or brain but it does give food for thought – or should that be less food for thought?
“We forget that three meals a day with snacks in between hasn’t exactly been the norm throughout human history..”
“There are a number of important messages we can take from these research findings,” says Associate Professor Samaras. “The first is that we shouldn’t chronically overeat, even if we are maintaining a healthy weight. The second is that it’s not unreasonable to periodically eat a bit lighter than usual.
“The third and perhaps most important is that studies in humans suggest that the health benefits of fasting were obtained by light, restricted eating, and not the sort of faddish longer term fasts of three days or more which can result in dangerous shifts in blood minerals and excessive loss of muscle mass.”
Have you tried fasting?