There have been a number of trials in laboratory animals –– the nematode Caenorhabditis elegans is the best example, but some work has also been carried out in flies and mice –– showing that caloric restriction extends the animal’s longevity by statistically significant amounts. A recent clinical study [see attached editorial] of people who reduced the number of calories that they consumed shows that these animal experiments are likely able to be extrapolated to humans.
The clinical trial [see attached editorial] has found the strongest evidence yet that such restrictions can slow down human metabolism. The results raise hopes that a low-calorie lifestyle — or treatments that mimic the biological effects of restricted eating — could prolong health in old age, and even extend life. Although such studies in animals having short life spans have demonstrated that calorie restrictions decrease metabolism and extend lifespan, experiments in longer-living humans and other primates are much more difficult to carry out (due to longer generation times) and therefore have not yet drawn clear conclusions.
The current study [see attached editorial] was part of the multi-center trial called CALERIE (Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy), sponsored by the US National Institutes of Health. The randomized, controlled trial tested the effects of 2 years of caloric restriction on metabolism in more than 200 healthy, non-obese adults. “The CALERIE trial has been important in addressing the question of whether the pace of aging can be altered in humans,” said Rozalyn Anderson, who studies aging at the University of Wisconsin–Madison. She leads one of two large, independent studies on calorie restriction in rhesus monkeys. “This new clinical report provides the most robust evidence to date that everything we have learned in other animals can be applied to ourselves.”
Other scientists are starting to test the restriction of calories for a few days each and every month. Such intermittent limitations have been found to be as effective as continuous calorie restriction –– in protecting mice against diseases of aging such as diabetes and neurodegeneration. This could be a way “to get all the benefits, without the problems of constant dieting,” but the jury is still out on these studies. The best advice is “Eat when you’re hungry, but stop eating when you no longer feel hungry.” 🙂
Nature 29 Mar 2o18; 555: 570–571