Alternate day fasting may help overweight patients lose nearly 8lbs in four weeks, research has found.
Volunteers were forced to starve for 36 hours before being allowed to indulge in whatever they wanted for 12 hours.
Overall, their calorie intake reduced by more than a third, helping them shed body fat without missing out on the foods they enjoyed.
They also had lower levels of chemicals in the body which have been linked to age-related diseases or inflammation.
Scientists believe it’s an easier way to lose weight than counting calories because some find it less restrictive – and they claim it helps because it is similar to the diet of cavemen, when food wasn’t available all the time.
Alternate day fasting helped overweight patients lose nearly 8lbs in four weeks and can improve internal markers of aging, scientists claim
Thomas Pieber, of the Medical University of Graz and co-author, said: ‘Why exactly calorie restriction and fasting induce so many beneficial effects is not fully clear yet.
‘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.’
In recent years there has been a surge of research into fasting diets, including intermittent fasting, 5:2 diet and alternate-day fasting (ADF).
Advocates claim they have lost weight as well as seen their stress reduce and energy rocket.
In the largest study of its kind to look at the effects of ADF in healthy people, the researchers recruited 60 people.
They were aged between 48 and 52 years and had an average body mass index of 25.5 – which would be considered just within the overweight band by the NHS.
For four weeks, one group was told to eat their normal diet – or as much as they wanted – while the other group were on the ADF diet.
The ADF group were monitored to make sure they didn’t consume any calories for 36 hours, before indulging in whatever they fancied for 12 hours.
WHAT INTERNAL MARKERS WERE IMPROVED?
After four weeks of alternate day fasting, participants had more ketone bodies, even on non-fasting days, which have been shown to promote health in various ways such as protecting the heart.
Ketone bodies, which are molecules produced by the body during fasting, have been found to have anti-aging effects on the vascular system, which could reduce the occurrence of diseases related to blood vessels, such as cardiovascular disease.
Scientists are also researching how ketone bodies may protect against Alzheimer’s.
The participants were found to have reduced levels of sICAM-1. This molecule has been linked to age-associated disease, including cardiovascular disease, and inflammation.
Another reduced hormone was triiodothyronine, which regulates metabolism.
Triiodothyronine is a hormone made partly by the thyroid gland and has previously been linked to longevity in humans.
Variations in thyroid function have been linked to an increased risk of cardiovascular disease and death.
The participants had reduced amino acids, in particular the amino acid methionine. This has been shown to extend the life of rodents in experiments.
To assess how ADF affects the immune system of people long term, the researchers had included a group of 30 people who had already practiced more than six months of strict ADF before the study.
Even after half a year, participants’ markers of immune function – such as white blood cells, monocytes and B cells – were stable.
They were also asked to fill in diaries documenting their fasting days.
Professor Harald Sourij, co-author, said: ‘We found on average, during the 12 hours when they could eat normally, the participants in the ADF group compensated for some of the calories lost from the fasting, but not all.’
Overall, participants following the diet consumed 37 per cent less calories and lost an average of 7.7lbs (3.5kg).
The participants also had slightly less belly fat, according to the paper published in the journal Cell Metabolism.
The investigators found several other positive effects not linked to weight.
For example, they had lower levels of sICAM-1, a molecule linked to age-associated disease, including cardiovascular disease and inflammation.
The researchers noted that ADF is ‘one of the most extreme diet interventions’, but potentially is more successful than just cutting calories.
However, calorie restrictive diets – where a person keeps within a calorie limit per day – can result in malnutrition, the researchers said.
There is also evidence it can compromise the immune system by reducing white blood cells.
ADF doesn’t appear to threaten the immune system this way, supporting previous findings.
Co-author Professor Frank Madeo said: ‘The reason might be due to evolutionary biology.
‘Our physiology is familiar with periods of starvation followed by food excesses.
‘It might also be that continuous low-calorie intake hinders the induction of the age-protective autophagy program, which is switched on during fasting breaks.’
Despite the findings, the researchers don’t recommend embarking on ADF for long periods until more research is done.
Professor Madeo said: ‘We feel that it is a good regime for some months for obese people to cut weight, or it might even be a useful clinical intervention in diseases driven by inflammation.
‘We advise people not to fast if they have a viral infection, because the immune system probably requires immediate energy to fight viruses.’
In the future, the researchers plan to study the effects of strict ADF in different groups of people including people with obesity and diabetes.