Hidden keys to living longer

As research into longevity continues to evolve, new findings challenge understanding of the complex relationship among diet, genetics, and lifespan, Science Alert highlights.

Reducing calorie intake and regularly delaying meals may be a beneficial approach to extending lifespan, though certain conditions may apply. A significant new animal study from the US involving nearly 1,000 mice indicates that while metabolic changes and decreased body mass can result from food restriction, these may also come with health risks for some individuals.

Numerous studies have shown that various animals—ranging from monkeys to fruit flies to mice and nematodes—tend to live longer when their food supply is restricted. However, due to ethical considerations and the complexities of clinical research, it remains uncertain whether similar dietary changes could extend human lifespans. Observational studies involving less extreme calorie restrictions, such as intermittent fasting, suggest that these practices may offer health benefits that could lower the risk of premature death.

Research indicates that reducing weight and body fat, along with lowering cardiometabolic risks, could significantly contribute to longevity. However, small sample sizes and brief study durations make it challenging to establish a direct link between these changes and increased lifespan. In their research, scientists examined the effects of varying levels of calorie restriction and intermittent fasting on 960 genetically diverse female mice, corroborating earlier findings that periodic hunger may lead to slightly longer lives. 

Mice on the most severe calorie restriction lost, on average, nearly 25 per cent of their weight by the age of 18 months, while those on a standard diet gained about 25 per cent more. Remarkably, the heavily restricted mice lived, on average, around nine months longer than their counterparts on regular diets—a roughly 33 per cent increase in lifespan. However, these averages obscure the significant variability within each calorie-restricted group. 

Although the ages of the heavily restricted mice spanned a wider range than their peers, some mice still died at various ages, suggesting that adverse factors might have overshadowed the benefits of calorie restriction. Interestingly, among the calorie-restricted mice, those that maintained more weight tended to live longer, indicating that metabolic regulation alone may not fully explain why calorie-restricted mice experience increased longevity. According to the authors, genetics played a much larger role in determining which mice reached old age. 

Mice that retained weight despite stressful handling had a higher likelihood of living longer, as did those with a higher proportion of infection-fighting white blood cells and more consistent red blood cell sizes. In simple terms, a resilient and well-equipped mouse was better equipped to navigate the challenges of life and enjoy a longer lifespan. 

The reasons why regular fasting or calorie reduction contributed to longer lifespans in some mice remain unclear. It appears to be a complex interaction of factors, likely more related to overall health than merely weight loss and metabolism. While it’s important to recognize the potential differences between mouse and human physiology, this study prompts a reevaluation of how we approach diet, health, and longevity. 

That said, there is still value in dietary restrictions for maintaining metabolic health. Even if genetics ultimately influence our chances of living to 99, prioritizing good health throughout our lives may be just as crucial—if not more so—than merely extending our years.

By Naila Huseynova