It seems as if half the population of the developed (and therefore obese) world is currently reading The Fast Diet, otherwise known as the 5:2 Diet, or Intermittent Fasting. The author, Michael Mosley, is a BBC journalist with a medical degree, and his documentary and book (co-authored by Mimi Spencer) seem interesting.
The rules are simple: for 5 days of the week, eat as you normally do, but twice a week, limit your food to 500 calories (for women) or 600 (for men). Someone I know tried it and found it worked. She even fasted a few times during a holiday in France – how’s that for dedication?
As Mosley points out, many religions include periods of fasting. During Yom Kipper, Lent, and Ramadan, the aim is similar in each case: to concentrate on spiritual rather than material things and – in extreme cases – to mortify the flesh. All require self-discipline, but they use quite different strategies.
At Yom Kippur, the Day of Atonement, Jews abstain from all food and drink if they can. This makes it the most rigorous of the 3 fasts, but it only lasts for a single day, from nightfall to nightfall.
During the month of Ramadan, which lasts for a lunar month, Muslims do not eat or drink anything between sunrise and sunset, but can eat and drink during the hours of darkness. Islam originated in Arabia, relatively close to the equator. Being lunar, the Islamic calendar gradually progresses through the seasons, and keeping Ramadan in summer becomes more onerous the further you move from the equator.
Lent lasts the longest, 40 days leading up to Easter. It involves a restricted diet without meat or dairy, but there is no limit on drinking water. It occurs at roughly the same time each year, the weeks of late winter and early spring (in the northern hemisphere).
Compared with these spiritual exercises, the idea of fasting to reduce weight or to improve health seems trivial, a travesty of a religious obligation. But in our secular world, it may be the only hunger many people will ever encounter. Maybe we should all go hungry occasionally, if only to experience what most people through most of the world’s history have experienced all too often.
To a surprising degree, our bodies were built for hunger.
Hunter-gatherers lived in a world of feast or famine. If the hunt was successful, or a particular food plant was plentiful, people ate well. In 1788, for instance, the Australian Aborigines ate better, with more variety and protein in their diet, than the convicts and soldiers who arrived to displace them. But there were gaps between the good seasons, when people had to rely on their food reserves, and people following the kangaroo or caribou can’t carry much food, except on their hips, buttocks and bellies. In hungry times that flesh melted away.
Agricultural societies also had their hungry months. Lent falls during this period, when the food stores are running low at the end of winter, the hens aren’t laying, domestic animals haven’t dropped their young, and spring crops aren’t ready yet. The Lenten fast made a virtue of necessity by restricting food intake just at the moment when there was no food to take in anyway.
Our bodies are still adapted to this pattern of feast and famine, but in the rich, developed world, there is never any famine now. No wonder we have an epidemic of obesity. There are other ways in which our past history makes itself known.
Vitamin D deficiency is a new and unexpected scourge in developed countries. Humans can make Vitamin D through the action of sunlight on our skin. Europeans’ pale skin was an evolutionary adaption that allowed their bodies to manufacture Vitamin D in northern latitudes, where the sunshine was weak.
In pre-industrial Europe, most people spent their lives in agriculture. During spring and summer, they worked in the fields, in the sun, building up a reserve of Vitamin D. The vitamin is fat-soluble. When food was plentiful in summer and autumn, people put on weight, and stored excess Vitamin D in their fat cells. Then in the dark winter months, when food supplies dried up, they began to go hungry, and lost weight as their fat reserves were used up. And as the fat was converted into energy, it released its store of Vitamin D.
Now, when we never go hungry, the fat stays on our hips, or worse because much more dangerous, as visceral fat in the abdomen. And Vitamin D – from sunshine, or food, or even supplements – is locked onto these fat cells and unavailable. We don’t have the severe deficiency that causes rickets in children, but in old people in particular, it is becoming a serious problem.
Most Australians are northern Europeans transplanted to a much sunnier climate. Our pale skin makes us vulnerable to skin cancers – Queensland is melanoma central. For 30-odd years, the message has been to stay out of the sun. ‘Slip, slop, slap’ was a hugely successful public health campaign.
Now the pendulum needs to shift back a little, to let the sunshine in. As for obesity, which is a problem throughout the developed world, perhaps a secular version of the intermittent fast might be a good idea. It could, at least, introduce us to the visceral experience of hunger – though whether it will deal with visceral fat, I’ll leave to the doctors for now.