Eating less long-term is more likely to help people live longer than periodic fasting, according to new research. Consuming fewer calories had a greater impact on lifespan than fasting, says new study.
They concluded that “more moderate” level of calorie restriction might be the way to balance long-term health and living longer following a study of mice. But losing weight may not be an indicator of a longer lifespan.
The American research, presented in the journal Nature, made an unexpected finding, the mice that lived longest under calorie-restricted diets were those that maintained their weight despite eating less food.
In contrast, the mice with the greatest weight loss from restricted diets appeared to experience diminished energy, weakened immune and reproductive systems, and ultimately led shorter lives.
The enduring mystery has been why such restrictive diets prolong life and how this could be applied to humans, given that almost a century of laboratory studies have consistently observed that eating less frequently or reducing food consumption leads to a longer lifespan in animals.
For the new study, scientists at The Jackson Laboratory (JAX) in Bar Harbor, Maine, tracked the health of more than 900 mice on a range of diets. The research was designed to ensure that each mouse was genetically distinct, which allowed the team to better represent the genetic diversity of humans.
The study concluded that eating fewer calories had a greater impact on lifespan than periodic fasting, revealing that very-low-calorie diets generally extended the mice’s lifespan regardless of their body fat or glucose levels – both typically seen as markers of metabolic health and aging. Research leader Professor Gary Churchill, of JAX, said: “Our study really points to the importance of resilience. The most robust animals keep their weight on even in the face of stress and caloric restriction, and they are the ones that live the longest.
“It also suggests that a more moderate level of calorie restriction might be the way to balance long-term health and lifespan.
Prof Churchill and his team put female mice on various diets, including unrestricted eating, daily calorie reductions to 60% or 80%, and intermittent fasting with one or two days without food each week.
The mice were then monitored until the end of their natural lives, undergoing regular health checks. Results showed that while mice on an unrestricted diet lived around 25 months, those on intermittent fasting reached about 28 months, those consuming 80% of their usual intake lived up to 30 months, and those on a 60% calorie diet lived the longest at 34 months.
Despite the groups, there was a broad range of lifespans, with mice consuming the least calories living anywhere from a few months to 4.5 years. The research team discovered that genetic factors had a “far greater” influence on lifespan than diet when they analysed their data to explain this wide range.
They suggest that their findings emphasise the significant role of yet-to-be-identified underlying genetic features in determining how these diets would impact an individual’s health trajectory.
The team identified genetically-encoded resilience as a “critical” factor in lifespan; mice that naturally maintained their body weight, body fat percentage and immune cell health during periods of stress or low food intake, as well as those that did not lose body fat late in life, lived the longest.
Prof Churchill stated: “If you want to live a long time, there are things you can control within your lifetime such as diet, but really what you want is a very old grandmother.”
The study also questioned traditional beliefs about why some diets prolong life. For instance, factors such as weight, body fat percentages, blood glucose levels and body temperature did not explain the connection between calorie restriction and longevity.
The study discovered that traits linked to red blood cells and immune system health have a stronger connection to lifespan. The researchers suggest that human longevity studies, which frequently use metabolic measurements as ageing or youthfulness indicators, might be missing key elements of healthy ageing.
Prof Churchill said: “While caloric restriction is generally good for lifespan, our data show that losing weight on caloric restriction is actually bad for lifespan. So when we look at human trials of longevity drugs and see that people are losing weight and have better metabolic profiles, it turns out that might not be a good marker of their future lifespan at all.”
Inputs with Hannah Giacardi and Neil Shaw, The Mirror
