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How Calorie Restriction Can Extend Life Span – But There’s a Catch
New Research Shows Genetics May Play a Bigger Role in Longevity
Eating fewer calories has long been associated with living a longer, healthier life. However, a groundbreaking study on mice shows that genetics may have a bigger influence on life span than diet alone. While eating less can extend life, it’s not as simple as just cutting calories.
The Study: Mice on Different Diets
Researchers from Jackson Laboratory, led by Gary Churchill, studied nearly 1,000 genetically distinct mice to see how different diets impacted their life span. The mice were divided into groups and placed on one of five diets:
- Unlimited food access
- 60% of their usual calorie intake
- 80% of their usual calorie intake
- Intermittent fasting (one day of no food, then unlimited food)
- Intermittent fasting (two consecutive days of no food, then unlimited food)
These mice were monitored throughout their lives, with regular blood tests and health assessments.
Caloric Restriction and Life Span
The results were striking. Mice on an unrestricted diet lived an average of 25 months, while those on calorie-restricted diets lived longer:
- Mice eating 80% of their usual calories lived about 30 months.
- Those eating 60% of their calories lived around 34 months.
However, the range of life spans within each group varied significantly, showing that factors beyond just calorie intake were at play. Some mice on the most restrictive diet lived up to 4.5 years, while others had much shorter lives.
Surprising Findings About Weight Loss
The study revealed an unexpected connection between calorie restriction and weight loss. While eating fewer calories extended life, the mice that lost the most weight tended to have shorter life spans. These mice had lower energy, weaker immune systems, and reduced reproductive health.
On the other hand, mice that maintained a healthy weight and immune system—even while eating less—lived the longest. This suggests that while reducing calories can be beneficial, losing too much weight might actually shorten life.
Churchill explained, “Our data shows that losing weight on caloric restriction is actually bad for life span. People often think weight loss equals better health, but in terms of longevity, that may not be the case.”
The Role of Genetics in Longevity
One of the key findings of the study was the significant role genetics play in determining life span. Mice that naturally kept their body weight and fat levels stable, even on low-calorie diets, lived the longest. These mice also had stronger immune systems and maintained overall health as they aged.
This highlights the importance of genetic resilience in longevity. While calorie restriction can help extend life, genetic factors play a large role in how well individuals respond to these diets.
Other Factors for a Long Life
The researchers also found that factors like immune system health and red blood cell traits were more closely linked to life span than weight, body fat, or blood glucose levels. These findings suggest that focusing solely on weight loss as a marker of health might be misleading.
As intermittent fasting and weight loss drugs like Ozempic become popular, it’s important to remember that good health involves more than just cutting calories.
Calorie Restriction Isn’t for Everyone
While the research shows some benefits of calorie restriction, it’s not a one-size-fits-all solution. Registered dietitian Emily Feivor, who wasn’t involved in the study, emphasized the importance of a balanced approach to health.
“Exercise and a balanced diet are crucial for improving overall health. Calorie restriction can increase the risk of malnutrition and other health problems, so it’s important to talk to a medical provider before making any changes to your diet,” Feivor explained.
This study offers valuable insights into the relationship between calorie intake and longevity, but it also highlights the importance of genetics and overall health. While eating less may help extend life, maintaining a healthy weight and immune system is key. It’s not just about reducing calories—other lifestyle factors like exercise and a balanced diet are equally important for a long, healthy life.
Sources:
- Jackson Laboratory Research
- Nature Journal Study
- Expert insights from dietitian Emily Feivor
