If you’re hungry for a new healthy-living fad, think fast
Jokes aside, intermittent fasting has proved in tests to improve the metabolism - but don’t do it to lose weight
When Twitter CEO Jack Dorsey tweeted that he does “a 22 hour fast daily (dinner only), and recently did a three-day water fast”, people hit back, asking how smart this was.
His approach is a stricter version of the 16:8 method: 16 hours of fasting (typically overnight) followed by eight hours of normal eating.
It’s no surprise that intermittent fasting is taking off among Silicon Valley geeks and medical profs alike (as well as other mortals). After all, neuroscientists have proved that this style of eating boosts and protects the brain.
Wits HIV professor Francois Venter is one of a group of world-renowned scientists and doctors to do this, typically eating normally for five days a week followed by two days of semi-fasting.
“We are senior researchers but not in the obesity field,” said Venter. “The hardcore data-driven people put their heads together and scientifically reviewed the literature on weight control and decided on [intermittent] fasting.
“It’s flexible to eat a quarter of the normal calories twice a week,” says Venter, whose sole interest in weight is how it affects his rock climbing. “Two days a week is much easier to do than starving for a week or a month.” Despite the trend towards intermittent fasting – typically two days a week, 16 hours a day or alternate days – results of a study published in January show that it is no better than conventional diets for losing weight.
It may be easier to follow than a “diet”. It may have greater health benefits – boosting your metabolism, protecting against degenerative brain disease and potentially slowing down ageing – but it’s not a shortcut to a slinkier you.
The German Cancer Research Centre and Heidelberg University Hospital ran a trial with 150 overweight and obese participants. Centre researcher Ruth Schübel said: “There are in fact only a few smaller studies on intermittent fasting so far, but they have come up with strikingly positive effects for metabolic health.
“This made us curious and we intended to find out whether these effects can also be proven in a larger patient group and over a prolonged period” using the 5:2 dietary plan.
“The result may be as surprising as it is sobering for all followers of intermittent fasting,” said Schübel. Both dietary groups lost the same amount of body weight, unhealthy belly fat (visceral fat) and extra fat in the liver, with no significant metabolic differences reported.
What the research did reveal is that a small weight loss, by whatever means, is a major health gain. People who reduced their body weight by only 5% lost about 20% of the “dangerous visceral fat and more than a third of the fat in the liver”.
Lead scientist Tilman Kühn said: “For some people it seems to be easier to be very disciplined on two days instead of counting calories and limiting food every day.”
That seems to be one reason why intermittent fasting, hyped by celebrities, is so popular. Former pro footballer Terry Crews, host of the Ultimate Beastmaster, follows the eat-drink-and-be-merry routine for eight hours (2pm to 10pm) and then eats or drinks no more for 16 hours (though he may remain merry). After the initial adaptation, intermittent fasting has also been shown to improve mood.
If mice were men, we would all be fasting given the significant and lasting anti-ageing effects shown in rodent studies – even after the mice went back to unrestricted eating and over-ate, in one experiment by the Longevity Institute at the University of Southern California.
Institute director Valter Longo has tested this model of semi-fasting – plant-based, lasting five consecutive days – not only on mice but also on himself, family and colleagues, with positive results.
An Australian study published in January, on alternate-day fasting – another kind of intermittent fasting – found it to be effective for weight loss. In that trial 88 obese women lost up to 10kg over 10 weeks by eating normally for 24 hours and then fasting for 24 hours after breakfast.
But alternate-day fasting could be risky for people with diabetes by impairing the action of sugar-regulating hormone insulin, researchers said at the European Society of Endocrinology meeting last year. People with eating disorders and children are among those who should avoid it.
Irene Labuschagne, from the Nutrition Information Centre at Stellenbosch University, said: “Any individual on chronic medication or at risk of developing low blood glucose levels (metabolic syndromes, diabetics, training athletes), pregnant women and children should discuss fasting with their health professionals. Prolonged fasting could lead to dehydration or inadequate nutrient intake.”
She said for people to realise its potential for weight loss they had to make sure they avoided too much or too little food during the re-feeding phases.
“Eating patterns that reduce or eliminate night-time eating and prolong nightly fasting intervals may result in sustained improvements in human health,” said Labuschagne.
What seems best for health – on this the gurus align – is a balanced approach to nutrition and meals that involves being mindful about what you eat and enjoying it.
But if you do have a Hansel and Gretel day, eating the equivalent of a candy house, fasting is sure to help your body reboot. Maybe even your brain.