October 22, 2024, 12:41 pm | Read time: 5 minutes
Intermittent fasting is not about specific foods but about time. Depending on the form of fasting, you are allowed to eat in certain time windows. And this is said to have numerous positive effects on health. A new study suggests that one form can even significantly prolong life. FITBOOK nutrition expert Sophie Brünke reports.
Have you ever tried intermittent fasting? Especially if you want to lose weight, you often come across this term. Studies to date suggest that this method has a positive effect on health and weight loss, particularly by reducing the breakdown of fat-free mass.1 Scientists at the Jackson Laboratory in Bar Harbor (Maine) recently published study results showing that intermittent fasting can also prolong life – at least when carried out in a certain way.
Overview
How eating less can affect lifespan
The authors of the study explain that eating less or less often has already been shown to prolong life in animals in previous research. However, why restrictive diets have this effect and how they can best be implemented in humans remains unanswered. Researchers at the Jackson Laboratory, an independent American research facility, are providing new insights into this question by studying 937 female mice. Mice representing a broad spectrum of genetic diversity were selected to represent the genetic makeup of humans and to better translate the results to humans.2
At the beginning of the study, the scientists divided them into five dietary groups:
- Group 1: unrestricted diet
- Group 2: 20 percent calorie restriction
- Group 3: 40 percent calorie restriction
- Group 4: one fasting day per week
- Group 5: two consecutive fasting days per week
With the exception of the two fasting days, the mice could eat as much as they liked. The mice were six months old at the start of the study and were fed and observed according to the assigned diet until their death. The researchers carried out extensive examinations of the health status of the mice throughout the study. For example, they recorded body composition, metabolic parameters, immune function, and other physiological markers.
Any calorie restriction could prolong life, but …
The study found that both time-independent calorie restriction and intermittent fasting were able to prolong the life of the mice. The effects were proportional to the degree of restriction. Mice with the highest restriction (group 3) also lived the longest. They lived around nine months longer than those who were allowed to eat as much as they wanted (group 1). Transferred to humans, this would correspond to an increase in lifespan of over a decade! The fasting mice in groups 4 and 5 also showed a significant increase in lifespan. This was despite the fact that they ate almost the same amount of food as mice in group 1.
The average lifespan of the groups at a glance:
- Group 1: 25 months
- Group 2: 30 months
- Group 3: 34 months
- Group 4: 28 months
- Group 5: 28 months
However, there were large differences in life expectancy within each group. Mice with the lowest calorie intake (group 3), for example, had a life expectancy ranging from a few months to four and a half years. Furthermore, their extreme calorie restriction of 40 percent also had potential negative effects. These included loss of muscle mass and changes in immune function. These are likely to be undesirable when used in humans. Fasting periods appear to be more suitable and can be integrated into everyday life.
Researchers discover unexpected factors influencing aging
As lifespan varied greatly within the groups themselves, the researchers looked for other influencing factors. Across all groups, the mice that lived the longest with reduced food intake were also those that lost the least body mass despite calorie restriction. Animals that lost a lot of weight had a shorter lifespan. Study author Churchill explains in a press release how important the body’s resilience is: “Our study highlights the importance of individual resilience. Robust animals maintain their weight even under stress and calorie restriction, and they also live the longest. It also suggests that moderate calorie restriction may be the way to balance long-term health and longevity.”3
Study results also raise new questions
The study results cast doubt on the idea that calorie restriction prolongs life mainly by protecting against the negative consequences of obesity. Instead, a reduced food intake could influence other mechanisms that have not yet been researched. In addition, the scientists’ data analysis showed that the genetics of the mice had a greater influence on lifespan than diet.
Classification of the study
As the study was only carried out on female mice, the results are not necessarily directly transferable to male mice and certainly not to humans. In addition, the study received support from Calico Life Sciences, a research and development company specializing in aging and age-related diseases. Several of the study authors are employed there, which may represent a conflict of interest. Some balance is provided by the involvement of other researchers from The Jackson Laboratory.
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Conclusion
It is important to recognize that calorie restriction can potentially extend lifespan. However, since drastic reductions of 40 percent can result in muscle mass loss and immune function alterations, a moderate approach, such as the intermittent fasting regimen studied, may be more appropriate for achieving this life-extending effect.
Interestingly, the study revealed that the typical health benefits linked to a calorie-restricted diet, like reduced body fat, were not the primary contributors to the extended lifespan observed. Instead, genetic factors had a far greater influence on longevity here and should be explored further. Churchill emphasizes the role of genetics in longevity. “While there are lifestyle factors you can manage throughout your life, like your diet, having a very old grandmother might be among the best predictors of a long life.”