Cutting calories and regularly skipping meals could be a successful strategy for adding years to life, but terms and conditions may apply.
A massive new animal study conducted in the US involving nearly 1,000 mice suggests that metabolic changes and reduced body weight are side effects of food restriction that can pose health risks to some individuals.
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Study after study has consistently shown that animals of all kinds, from monkeys to fruit flies to mice to nematodes, live longer when their food supply is limited.
However, given the ethics and challenges of clinical trials, it is difficult to say whether eating less could also increase a person's lifespan.
Observational studies using less extreme caloric restriction, such as intermittent fasting, suggest that dietary restriction has benefits that may reduce our own chances of ending up prematurely.
Health studies also show reductions in weight and body fat and reduction in cardiometabolic risks, which can play a major role in extending life. But small samples and limited study periods make it difficult to say whether these changes are directly responsible for the extended lifespan.
The researchers evaluated the effects of gradual caloric restriction and intermittent fasting on 960 genetically diverse female mice, confirming the findings of many previous studies, which claimed that occasionally maintaining the body in a slightly hungry state led to a slightly longer lifespan.
Those on the greatest calorie reduction lost, on average, nearly a quarter of the weight they had at 6 months by 18 months, whereas mice on a normal diet gained just over a quarter of their weight. weight.
Notably, the severely restricted mice also lived an average of about 9 months longer than those on the normal diet—a little more than a third.
What the averages don't show are the differences within each calorie-controlled group. Although the increase in age in the strict-diet population exceeded that of their peers, several mice died at different ages, almost as if the downsides had benefited from the lower calorie intake.
In fact, in the calorie-restricted groups, it was the mice that gained the most weight that died later, suggesting that metabolic regulation is unlikely to explain why the calorie-restricted mice lived longer.
The authors report that genetics played a much larger role in determining which mice lived to adulthood. Mice that maintained their weight as a result of the strenuous activity were more likely to live longer, as were those that had a higher proportion of infection-fighting white blood cells and a smaller difference in red blood cell size.
Simply put, a hardy, well-cared-for mouse is more likely to survive the rigors of life and live longer.
The question is why regular fasting or reduced calories helped some mice live longer. No doubt it's a complex interplay of factors that are apparently more disconnected from weight loss and metabolism than we thought.
Bearing in mind the potential differences between mouse and human physiology, the study should give pause to how we think about our diet, health and lifespan. This does not mean that there is no place for dietary restrictions to keep the metabolism in order.
Even though our genes have the ultimate say in our chances of seeing our 99th birthday, maintaining good health throughout our lives is arguably as important as counting the years, if not more so.