Alternating fasting during the day can help overweight patients lose nearly 8 pounds in four weeks, research has shown.
Volunteers were forced to starve for 36 hours before they could enjoy 12 hours.
In general, their calorie intake has been reduced by more than a third, so they lose body fat without missing the food they liked.
They also had lower levels of chemicals in the body that have been associated with age-related illnesses or inflammations.
Alternating fasting on the day helped overweight patients lose nearly 8 pounds in four weeks and could improve internal markers of aging, scientists claim
Scientists in Austria believe that it is an easier way to lose weight than counting calories, because some find it less restrictive.
Thomas Pieber, from the Medical University of Graz and co-author, said: “Exactly why calorie restriction and fasting cause so many beneficial effects is not entirely clear.
& # 39; The elegant thing about strict ADF is that participants don't have to count their meals and calories: they just eat nothing for one day. & # 39;
In recent years a lot of research has been done on fasting diets, including intermittent fasting, 5: 2 dieting and alternating fasting (ADF).
Proponents claim that they have lost weight and that their stress and energy rocket are declining.
In the largest study of its kind to look at the effects of ADF in healthy people, the researchers recruited 60 people.
They were between 48 and 52 years old and had an average body mass index of 25.5 – which would be considered by the NHS just within the overweight band.
For four weeks, one group was told to eat their normal diet – or as much as they wanted – while the other group followed the ADF diet.
The ADF group was monitored to ensure that they had not consumed calories for 36 hours before they could live out for 12 hours.
WHAT INTERNAL MARKERS ARE IMPROVED?
After four weeks of alternating 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, molecules produced by the body during fasting, appear to have anti-aging effects on the vascular system, which could reduce the occurrence of blood vessel related diseases, such as cardiovascular disease.
Scientists are also investigating how ketone bodies can protect against Alzheimer's disease.
The participants were found to have reduced levels of sICAM-1. This molecule has been associated with age-related diseases, including cardiovascular disease and inflammation.
Another lowered hormone was triiodothyronine, which regulates metabolism.
Triiodothyronine is a hormone that is partially produced by the thyroid gland and is previously linked to a long life in humans.
Variations in thyroid function have been associated with an increased risk of cardiovascular disease and death.
The participants had reduced amino acids, in particular the amino acid methionine. Experiments have shown that this extends the lifespan of rodents.
To assess how ADF affects people's immune systems in the long term, the researchers included a group of 30 people who had been practicing strict ADF for more than six months before the study.
Even after six months, the participants' immune function markers – such as white blood cells, monocytes and B cells – were stable.
They were also asked to fill in diaries that documented their fast days.
Professor Harald Sourij, co-author, said: “We found that on average during the 12 hours that they could eat normally, participants in the ADF group compensated for some of the calories lost due to fasting, but not all. & # 39;
In general, participants on the diet consumed 37 percent fewer calories and lost 3.5 kg on average.
Participants also had slightly less abdominal fat, according to the article published in the journal Cell Metabolism.
The researchers found several other positive effects that were not related to weight.
For example, they had lower levels of sICAM-1, a molecule linked to age-related diseases, including cardiovascular disease and inflammation.
The researchers noted that ADF & # 39; one of the most extreme dietary interventions & # 39; is, but possibly more successful than just cutting calories.
However, calorie-restricted diets – where a person keeps within a calorie limit per day – can lead to malnutrition, the researchers said.
There are also indications that it can endanger the immune system by reducing white blood cells.
ADF does not appear to threaten the immune system in this way and supports earlier findings.
Co-author Professor Frank Madeo said: & The reason may be due to evolutionary biology.
& # 39; Our physiology is familiar with periods of starvation followed by food surpluses.
& # 39; It is also possible that continuous low-calorie intake impedes the induction of the age-protecting autophagy program, which is switched on during fasting breaks. & # 39;
Despite the findings, the researchers do not recommend starting ADF for a long time until more research has been done.
Professor Madeo said: & # 39; We think that for some months it is a good regime for obese people to reduce weight, or it may even be a useful clinical intervention for diseases caused by inflammation.
& # 39; We advise people not to fast if they have a viral infection, as the immune system probably needs immediate energy to fight viruses. & # 39;
In the future, the researchers plan to study the effects of strict ADF on different groups of people, including those with obesity and diabetes.
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