For the first time healthy adults have taken part in a scientific trial which restricted their daily intake of food and drink by a quarter, over two years, and the results show their risk of dying dropped 10-15%.
The pace of ageing slowed by 2-3% among participants in the clinical trial in the US. This equals a 10-15% reduction in mortality, based on prior research, similar to the benefits of quitting smoking.
“Our study shows that it may be possible to modify the pace of biological ageing through a behavioural intervention,” senior author and epidemiology professor Dan Belsky, from Columbia University in New York, told TimesLIVE Premium.
“There have been many trials of calorie restriction in adults with obesity, and there have been a few short-term trials in healthy adults, [but] the CALERIE Trial is the first randomised controlled trial of long-term calorie restriction in healthy, non-obese human adults,” he says.
“In worms, flies and mice, calorie restriction can slow biological processes of ageing and extend healthy lifespan,” states Belsky, a scientist with Columbia’s Butler Aging Center.
Rhesus monkeys, however, did not live longer after an extreme diet, a long-running study by the University of Texas found 10 years ago.
Our study shows it may be possible to modify the pace of biological ageing.
— Prof Dan Belsky, Columbia University's Butler Aging Center
In the latest trial, 220 people from three sites in the US were randomised into two groups — those on a 25% calorie-restriction diet (relative to their baseline) or those on a normal diet — and had blood analysed before the trial launched, after 12 months and 24 months.
Columbia research scientist Calen Ryan, co-lead author of the study, notes that “calorie restriction is probably not for everyone”. Unlike daily life, trial volunteers had the monitoring of trained experts for two years.
Physicians who specialise in obesity-related diseases — most of which can be reversed with weight loss — say long-term data shows it is hard to sustain weight loss over time. Only about 5% of people manage to control their weight effectively long term with lifestyle changes, such as exercise and calorie restrictions, they observe.
For people to consume 25% fewer calories a day would be very difficult without medication or bariatric surgery, according to them.
Evidence has been growing in smaller and uncontrolled studies that restricting calories puts the brakes on ageing, and the latest data — from measuring participants’ blood DNA methylation, a molecular process associated with ageing — supports this trend.
“Humans live a long time,” says Belsky, “so it isn’t practical to follow them until we see differences in ageing-related disease or survival. Instead, we rely on biomarkers developed to measure the pace and progress of biological ageing.”
The international team found their intervention “slowed the pace of ageing” (measured by the DunedinPACE DNAm algorithm) but did not result in significant changes in biological age estimates (measured by DNAm clocks like GrimAge).
The study, published in Nature Aging, will show researchers what biomarkers to look for when other interventions, such as intermittent fasting, are investigated, says Ryan.
The team is following up with the CALERIE participants to investigate any long-term effects on healthy ageing. The trial name, CALERIE, stands for the comprehensive assessment of long-term effects of reducing intake of energy.
Senior scientist Krupa Das, the CALERIE investigator leading the follow-up, says they will test if the short-term effects last into a longer-term reduction in risks and age-related chronic diseases, such as diabetes.
Belsky recommends: “For those of us interested in changing our lifestyle to promote healthy longevity, the best advice is still some combination of Michelle Obama’s ‘move more’ and Michael Pollan’s ‘eat food, mostly plants, not too much’.”
Would you like to comment on this article?
Sign up (it's quick and free) or sign in now.
Please read our Comment Policy before commenting.