Fasting every other day could be the secret to losing weight while staying healthy because it mimics humans’ caveman diet, a new study suggests.
A trial showed that people who ate no food at all for 36 hours then anything they felt like for 12 hours lost more than half a stone within a month.
Crucially, their immune systems remained stable, even after six months, in contrast to many diets which aim to restrict calorie intake consistently each day.
Scientists at the University of Graz in Austria believe the strength of alternate-day fasting (ADF) may lie in its adherence to hunter-gatherers’ patterns of eating thousands of years ago, when food was not available every day.
However, they warn that it may not be suitable for everyone and that further studies need to prove its safety over the long-term.
Does fasting really work?
Fasting for four to five days at a time can cut cholesterol and blood-pressure levels, and reduce the likelihood of cardiovascular disease. The way it works is simple. After 48 hours of fasting, the body has exhausted its glucose reserves and turns to other energy sources.
First, it uses up the fat stores, then muscle. Next the organs, including the liver and pancreas, start to break down. By day five of a fast, a mass of cells will have died, leading to a reduction in ‘bad’ components like excess glucose (which can lead to type 2 diabetes), IGF1 (a growth factor associated with cancer) and triglyceride (the unwanted fat component of blood cells).
Once you start eating again, your body regenerates new cells. In effect, the process serves as an MOT, as the old cells are replaced with healthy ones.
However, there are risks that come with fasting, including hypoglycemia (dangerously low blood-sugar levels) and heart palpitations; and those taking medication for high blood pressure or diabetes are at risk of hypertension (abnormally low blood pressure).
People over the age of 70, or anyone with anorexia, should not fast at all. Everyone should seek advice from a medical professional before fasting.
Published in the journal Cell Metabolism, the study recruited 60 participants who were enrolled either into an ADF group or into a control group where they were were allowed to eat whatever they wanted.
The ADF group were required to fill in food diaries and also underwent continuous glucose monitoring to ensure they stuck to the routine.
The scientists found that, on average, the dieters ate normally during the 12 hours they were at liberty to eat an unlimited amount.
Overall, they reached an average calorie restriction of around 35 per cent and lost an average of 7.7 lb or 3.5 kg after four weeks of the programme.
“Why exactly calorie restriction and fasting induce so many beneficial effects is not fully clear yet,” says Professor Thomas Pieber, head of endocrinology at the Medical University of Graz.
“The elegant thing about strict ADF is that it doesn’t require participants to count their meals and calories: they just don’t eat anything for one day.”
His colleague, Professor Frank Madeo, added: “The reason might be due to evolutionary biology.
“Our physiology is familiar with periods of starvation followed by food excesses.”