The fixation with slimness maybe a more recent trend but our longing for longevity dates back to ancient times, when sages and hermits lived unusually long on frugal diets and were revered, among other things, for this ability. Today, a strong correlation is emerging between frugality of diet and longevity.
Does eating less but well mean living longer?
The first evidence that human (mammalian, actually) longevity could be increased came in 1935: A rodent study showed that restricting calories without malnutrition could delay the onset of diseases and extend life. Since then, scientists have studied various model organisms, which have shed light on how caloric restriction, or CR, retards the process of ageing in humans.
In the latest issue of Science (10 July), scientists reported that a 20-year study on rhesus monkeys showed substantially reducing caloric intake leads to longer lifespans in primates. This not only supports the earlier studies in yeast, worms, flies and rodents, but opens up opportunities for clues to delaying ageing and onset of related diseases in humans. After all, there are many parallels between monkeys and humans.
“Given that it has proven successful in this broad array of species, I find it likely that it would be successful in humans as well,” says study co-author Rickie Colman from the University of Wisconsin. His team claims that CR reduced the risk of developing an age-related disease by a factor of three and increased survival.
No easy sum
The term CR is deceptively simple. Despite what the name might suggest, it’s not only about restricting calories. Though the average reduction is about 30%, the right percentage of calorie cutback for each individual needs to be decided and implemented gradually, over a period of time. This is tricky, especially if you are a Google worshipper and find salvation in the search engine. You’ll find several CR calculators online, but it’s equally easy to get lost. For instance, can you accurately identify your activity level—lightly active or moderately active, very active or extra active? Let’s admit, we all tend to overestimate it. The food also has to be of the right mix so that calories are low, and nutrition high.
Nor a panacea
As an anti-ageing intervention, CR is years away from clinics; but as an experimental disease-preventing mechanism it could work, maybe selectively. Earlier studies have shown, rather convincingly, that a very low-calorie but nutritionally balanced diet is heart-healthy. CR makes the heart “elastic” and “relaxed between beats”, just as is the case naturally in younger people. These structural changes mitigate age-related decline in heart function.
Also Read earlier Breaking Through columns
The monkey study, one of the most exhaustive till date, provides the most detailed insight into the phenomenon of caloric intake vs ageing. The results are gender neutral: Both men and women benefit equally. More importantly, it is effective in middle age, that is, a low-calorie diet started at any point in adulthood will bring rewards.
At the cellular level, CR affects indicators of mortality (cancer, diabetes, cardiovascular diseases and brain atrophy) which, if delayed, would lead to longer life. The study showed complete prevention of diabetes in the animals and remarkable brain health. Because humans live much longer than monkeys and their environment cannot be controlled fully, researchers believe conclusive evidence of the effects of the diet on human lifespan and disease may never be known.
Incidentally, calories burnt in exercise do not have the same effect as CR; nor do they enhance its life-extending benefits. So, the question is: Would one want to eat less to add a few years to their life? Philosophically, the answer may be no. But most of us can benefit from modest curbs with full freedom to enjoy a chocolate now and an ice-cream later.
The author is Mint’s deputy bureau chief in Bangalore. Write to her at firstname.lastname@example.org