Restricting the amount of calories consumed might slow down ageing in humans, research suggests.
According to the study, cutting calories by a quarter resulted in the pace of ageing slowing by around 2% to 3%, which represents a 10% to 15% reduction in the risk of death.
This effect is similar to that of giving up smoking, the researchers say.
But experts warn that it is important to be cautious and not encourage people, particularly older people, not to eat less in order to slow down the ageing process.
While a reduced calorie intake appeared to reduce the pace of ageing, this did not translate to an increase in estimated lifespan.
Senior author Daniel Belsky, associate professor of epidemiology at Columbia Mailman School of Public Health and a scientist with Columbia’s Butler Ageing Centre, said: “In worms, flies, and mice, calorie restriction can slow biological processes of ageing and extend healthy lifespan.
In a first-of-its-kind trial, an international team of researchers led by the Butler Columbia Ageing Centre at the Columbia University Mailman School of Public Health found that calorie restriction can slow the pace of ageing in healthy adults.
The trial involved 220 healthy men and women at three sites in the US on either a 25% calorie-restricted or normal diet for two years.
At baseline, people were typically eating just over 2,000 calories per day.
CALERIE, the name of the study, is an acronym for: comprehensive assessment of long-term effects of reducing intake of energy.
To measure biological ageing, researchers analysed blood samples collected at the start of the trial and after 12 and 24 months of follow-up.
Prof Belsky said: “Humans live a long time, so it isn’t practical to follow them until we see differences in ageing-related disease or survival.
The team analysed chemical tags on the DNA that regulate the expression of genes and are known to change with ageing.
Calen Ryan, co-lead author of the study, said: “Our study found evidence that calorie restriction slowed the pace of ageing in humans.
“But calorie restriction is probably not for everyone. Our findings are important because they provide evidence from a randomised trial that slowing human ageing may be possible.
“They also give us a sense of the kinds of effects we might look for in trials of interventions that could appeal to more people, like intermittent fasting or time-restricted eating.”
The findings are published in the Nature Ageing journal.
Dr Duane Mellor, registered dietitian and senior lecturer, Aston Medical School, Aston University, said: “This is an interesting study which looked at 220 people aged between 21-50 years old, who were randomised to a 25% energy (calorie) restriction for two years or to eat to their appetite.
“It is difficult to interpret the data in this study, to tell how the data reported in this study matched to the diets people actually stuck to, only that those told to eat less were reported to have DNA that aged slightly, but significantly more slowly.”
He added: “Although interesting, it is important to be cautious and not encourage especially older adults just to reduce their food intake to slow ageing.
“As, in ageing adults, maintaining a healthy weight, being physically active and eating a varied and healthy diet with enough protein is known to reduce the risk of falls.”
Naveed Sattar, professor of metabolic medicine, University of Glasgow, said: “This seems well done research on complex markers in the context of a small scale calorie reduction trial, but do we really need to prove that eating less calories slows aging processes?
“This should be evident from national data sets that show people from Japan who remain leaner than most are amongst the longest living of any nation.”
He added that the findings are in keeping with “an emerging body of evidence all pointing in the same direction”.