Paris – Mouse lemurs that subsist on fewer calories throughout adulthood live longer than their peers, said a study published on Thursday, feeding into an ongoing debate about diet and longevity.
Calorie-restricted lemurs were physically younger in old age and less afflicted by diseases such as cancer or diabetes, the research found – though they also lost grey matter faster.
"The present results provide evidence that chronic, moderate (30%) caloric restriction, when started early in adult life, can extend the lifespan of mouse lemurs by 50%" compared to non-dieting peers in captivity, said a paper published in the journal Communications Biology.
Accelerated grey matter loss, a potentially worrying side-effect, had no obvious impact on the animals' cognitive abilities, the French research team added.
Restricting calorie intake – reducing food without losing essential nutrients or inducing malnutrition – has already been shown to boost lifespan in short-lived species such as rats, and to improve the general health of some animals.
However there have been contradictory findings about whether cutting calories boosts longevity in rhesus macaques – long-lived animals with an average life expectancy of 27 years in captivity and 40 in the wild.
A 2012 paper, reporting on 23 years of study, concluded that a 30% calorie-restricted diet made macaques healthier, but did not prolong their lives.
This directly contradicted research by the Wisconsin National Primate Research Centre, which found calorie-restricted macaques did in fact live longer than their peers.
The jury is out on the potential benefits for humans.
The French team sought to build on the body of research by looking at grey mouse lemurs which, along with humans and macaques, are members of the primate family.
Far beyond max lifespan
On average, the Madagascan primate lives about 5.7 years in captivity and about 12 years in the wild.
The study started in 2006, with 15 animals assigned a "standard" daily diet consisting of 6g of fresh fruit and 15g of a special mixture of ginger bread, cereal, milk, and eggs – a total of 105kJ.
Another 19 lemurs were fed the same food, but 30% less – 71kJ per day.
The animals were enrolled in the study as young adults, aged just over three years.
The scientists found that the calorie-restricted lemurs lived to 9.6 years on average, compared to 6.4 years for those on the standard diet.
By the end of the study, all 15 standard diet lemurs had died, while seven calorie-restricted lemurs were still alive.
All seven reached the age of 13, "which is far beyond the maximal lifespan" recorded, the study said.
Loss of white matter – connective tissue allowing different regions of the brain to communicate – was slowed in the calorie-restricted lemurs, the researchers found.
But loss of grey matter – the brain's wrinkly outer layer which houses the processes of learning and memory, motor function, social skills, language and problem solving – was accelerated.
This pointed to "a potential negative impact of caloric restriction on brain integrity that deserves more investigation", the team said.
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