For almost a century, laboratory studies have shown consistent results indicating that eating less or less frequently prolongs the life of animals. However, scientists have struggled to understand why these restrictive diets prolong life and how to best apply them in humans.
Now, researchers at the Jackson Laboratory (JAX) and collaborators have conducted a key study on aging and longevity to uncover new details about how diets could help you live longer, but also their negative side effects. The findings have been published in the journal Nature.
The team of scientists monitored the health of almost a thousand mice fed different diets to delve deeper into these questions. The study was designed so that each mouse was genetically unique, allowing the team to better represent the genetic diversity of the human population. This makes the results more clinically relevant, elevating the research to one of the most important in the field of aging and longevity to date.
The research conclusions highlight that consuming fewer calories had a greater impact on longevity than intermittent fasting and that very low-calorie diets prolonged the life of the mice regardless of their levels of body fat or glucose, indicators that are usually considered signs of metabolic health and aging.
Surprisingly, the mice that lived the longest on these restrictive diets were those that lost the least weight despite eating less. In contrast, those who lost more weight showed lower energy levels, weakened immune and reproductive systems, and shorter lifespans.
Losing weight with calorie restriction is bad for longevity
“Our study really highlights the importance of resilience,” said Gary Churchill, Karl Gunnar Johansson Chair and Professor at JAX, who led the research. “The most robust animals maintain their weight even in the face of stress and caloric restriction, and they are the ones that live the longest. “This suggests that a more moderate level of calorie restriction may be the best way to balance long-term health and life expectancy.”
Churchill and his colleagues assigned the mice to five different diets: one in which they could eat freely at any time, two in which they received only 60% or 80% of their usual daily calories, and two in which they were not fed. I gave them food for one or two consecutive days each week, but they could eat as much as they wanted on the other days. The mice were then studied for the rest of their lives with periodic blood tests and detailed assessments of their general health.
Overall, mice on unrestricted diets lived an average of 25 months, those on intermittent fasting lived an average of 28 months, those eating 80% of their usual calories lived 30 months, and those eating only 60% lived. 34 months. However, within each group, longevity varied considerably; For example, some mice that ate fewer calories lived just a few months, while others lived up to four and a half years.
“If you want to live a long time, there are things you can control, like diet, but what you really need is a grandmother who has lived a long time.”
Analyzing this data, the researchers found that genetic factors influenced longevity more than diets, highlighting the crucial role of genetic characteristics in how these diets could affect a person’s health. Furthermore, they identified that genetic resilience was a key factor in longevity; Those mice that maintained their weight, body fat percentage, and immune health during periods of stress or lack of food lived longer. “If you want to live a long time, there are things you can control, like diet, but what you really need is a grandmother who has lived a long time,” Churchill added.
The study also challenged traditional ideas about why certain diets prolong life. Factors such as weight, body fat levels, blood glucose and body temperature did not explain the connection between calorie reduction and longevity. Instead, immune system health and red blood cell-related characteristics showed a clearer connection to life span. This suggests that human longevity studies may be overlooking more important aspects of healthy aging by focusing on metabolic measurements.
“Although calorie restriction in general is beneficial for longevity, our data show that losing weight with calorie restriction is actually bad for longevity,” Churchill explained. “So, when we look at human trials of longevity drugs and see that people are losing weight and have better metabolic profiles, that may not be a good indicator of their future life expectancy at all,” the study concludes. researcher.
