The way we eat has a huge impact on our health and quality of life. This is true for humans and other mammals. For decades, lab studies on animals have shown that eating less food leads to longer life. In an attempt to understand why this is so and whether the link between calorie intake and lifespan in animals applies to humans, a team of scientists from the Jackson Laboratory (JAX) at Harvard University monitored the health of almost a thousand mice. All subjects were kept on various diets, and their health and lifespan were monitored. It turned out that calorie restriction and intermittent fasting really do help animals live longer. But do these results apply to humans?
Calorie Restriction and Intermittent Fasting Affect Life Expectancy. Image: theweek.in
Contents
- 1 Obesity, Nutrition, and Ozempic
- 2 Diet and Lifespan
- 3 Nutrition and Lifespan of Mice
- 4 Of Mice and Men
Obesity, Nutrition, and Ozempic
The world is raging with an obesity epidemic. Earlier, experts from the World Health Organization (WHO) stated that over the past 32 years, the level of obesity in the world has more than doubled among adults and quadrupled among children. Against this background, the injectable drug “Ozempic” has gained immense popularity. Its main active ingredient, semaglutide, helps the pancreas produce insulin.
But “Ozempic” was originally developed to treat type 2 diabetes, and weight loss drugs with the same active ingredient appeared later, mainly due to the popularity of its predecessor (which many people used for other purposes and experienced unpleasant side effects). It turns out that “Ozempic” did not become a magic weight loss pill.
Against the backdrop of the obesity epidemic, drugs like Ozempic and various diets are enjoying unprecedented popularity. Image: times.brightspotcdn.com
More on the topic: What happens to the body after you stop taking a famous weight loss drug?
Yes, yes, like it or not, it is our eating habits that have a significant impact on our weight and overall health. That is why diets and intermittent fasting are still popular. But are diets associated with longevity? And if so, what does this mean?
Diet and life expectancy
As discussed above, previous animal studies have shown a link between calorie-restricted diets and lifespan. However, such diets pose a number of problems when it comes to interpreting the results for humans.
The first thing that comes to mind is intermittent fasting. The fact is that scientists have confirmed the benefits of calorie deficiency: intermittent fasting in humans and animals really does have a positive effect on various body systems. However, the connection between fasting and human longevity has not been studied to a large extent.
Intermittent fasting helps you lose weight and feel better. But is it linked to longevity? Image: bloximages.newyork1.vip.townnews.com
To get to the bottom of this complex topic, the authors of a study published in the journal Nature monitored the health and longevity of nearly 1,000 genetically diverse mice to compare the effects of calorie restriction and intermittent fasting.
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Nutrition and lifespan of mice
The research team wanted to understand how genetically diverse mice (they are more similar to humans than “regular” lab mice) would respond to dietary intervention. All subjects were randomly assigned to one of five diets: unlimited access to food, fasting one day a week, fasting two days in a row per week, restricting caloric intake by 20% and by 40%.
Note that calorie restriction involves a constant reduction in calories by a certain percentage of the daily norm. Intermittent fasting, in turn, involves alternating periods of normal food intake and fasting.
Eating fewer calories made the mice healthier, but genetics were the main player. Image: elpais.com
It turned out that the mice on a restricted diet were, on average, healthier and lived longer. However, there were consequences – a decrease in body temperature, changes in the blood, the immune system and behavior. This is why scientists suggested that the animals on the diet were more susceptible to infections.
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Interestingly, not all mice had the best health indicators and lifespan. Despite the health benefits of calorie restriction, genetics was the main factor in longevity: its impact on lifespan was three times greater than dietary intervention.. Moreover, even the improved metabolic parameters associated with the diet (blood glucose levels and body fat) do not appear to be directly related to longevity.
The dietary intervention used in the mice study is not suitable for humans. Even a one-day fast or 20% calorie restriction, if translated into human equivalents, is not advisable for humans in the long term, the authors of the study clarified.
Thus, the obtained results showed that intermittent fasting and calorie restriction lead to an increase in the lifespan of mice. The stricter the restriction, the more pronounced the effect. Moreover, it was not nutrition but genetic factors that had the greatest influence on longevity.
Nutrition and longevity are linked, but they are different. Image: newsweek.com
It’s important to note that health and longevity are not the same thing. Some markers of the mice’s health improved during the experiment, but they didn’t always correlate with longer lifespan. The team also found side effects of severe calorie restriction: although mice on 40% fewer calories lived longer, they experienced muscle loss and changes in their immune systems.
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Overall, the mice that ate ad libitum lived for 25 months. Their intermittently fasted counterparts lived for an average of 28 months, and the mice that consumed 80% of their calories from their original diet lived for an average of 30 months. The mice that consumed 60% of their calories from their original diet lived the longest, 34 months.
Of Mice and Men
The results of the study suggest that the mechanisms underlying the life extension benefits of calorie restriction and intermittent fasting are more complex than simple weight loss, and better health outcomes do not always predict longer life (and vice versa). Moreover, extreme calorie restriction leads to serious health problems.
Loss of muscle mass and weakened immunity are serious risks that must be taken into account, the scientists wrote.
Because genetics play a significant role in how we respond to food intake, there is no one-size-fits-all approach to diets that promote longevity. This is likely true for both mice and humans. While animal studies provide valuable information, the results are not generalizable to humans. Long-term studies and clinical trials are needed to understand how intermittent fasting and diets affect human health and longevity.
Tell me what you eat, and I'll tell you who you are. Image: worldhealth.net
Nevertheless, the results of the Jackson Laboratory team provide valuable data on how calorie restriction and intermittent fasting affect longevity and health, emphasizing the importance of genetic factors and individual characteristics. All this means that the safest and most effective approach for our health and longevity is moderation in nutrition and attention to the body.
Do you think there is a limit to human lifespan? Read the answer in the article by my colleague Andrey Zhukov!
The authors of the work also noted that longevity studies in humans, which often use metabolic rates as markers of aging or youth, may miss more important aspects of healthy aging.
While calorie restriction is considered beneficial for longevity, our data showed that weight loss with this approach actually negatively affects lifespan, the scientists concluded.