Restricting calorie intake adds no years to life, unless begun early in life: Study

If you are among those who have cut down on food intake for a healthier and longer life, there is some good news and bad news for you.

Scientists studying how diet restrictions help add years to life have found – at least in animals – that restricting the calorie intake extends the lifespan by 25 to 30 per cent. But the bad news is that unless the lean diet is followed right from young age, it’s probably of no use.

“Health in old age is a life-long affair,” said Sebastian Grönke, a researcher with the Max Planck Institute for Biology of Ageing in Germany, who, along with others showed that switching to a restricted diet in old age offered no benefit.

The team, which also included scientists from the Babraham Institute at Cambridge in the UK, the University of Cologne in Germany and Stanford University, among others, investigated the effects of dietary restrictions on 800 female mice that were 24 months old, an equivalent of well-past-mid-life in humans.

Some mice were switched from an unrestricted to a restricted diet or vice versa. Mice switched from a restricted diet to an unrestricted diet quickly became unhealthy and died earlier than those that remained on a restricted diet. However, even though they were healthier, the mice switched from an unrestricted to a restricted diet did not live longer than mice that remained on an unrestricted diet.

The authors found that the molecular response to a restricted diet was different in the fat tissues of the mice previously given unrestricted access to food for most of their life. The scientists proposed a ‘nutritional memory effect’ in fat tissue that suppresses the beneficial effects of dietary restrictions on health and survival.

“In our study, we show that diet restriction initiated at old age provides almost no benefit for survival, while mice that were kept on a restricted diet for their whole lives, showed an extended lifespan of about 25-30 per cent,” said Grönke. The findings were reported in a study that appeared in the journal Nature Metabolism on Monday night.

According to Grönke, there could be several reason why old animals are no longer responsive to the benefits of the restricted diet late in life. They found that the fat tissue of old animals did not respond to restricted diet in the same way as it did in young mice.

“Normally, diet restriction increases the number of mitochondria, cellular organelles important for energy production, in the fat tissue. Mitochondria play an important role in lifespan regulation and the failure to upregulate it in old animals may thus contribute to the lack of a beneficial effect,” Grönke told BusinessLine.

He was however, quick to add that it was not yet clear whether diet restrictions also extend the lifespan in humans. But, it improves health in the same way as it does in mice. “Our study suggests that dietary interventions that improve health should be started relatively early in life, which is likely also the case for humans,” said the Max Planck Institute scientist.

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