Who moved their cheese?
A pivotal new study that subjected mice to a variety of diets found that genetic factors had a far greater effect on their lifespan than eating habits.
“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,” said study leader Gary Churchill of Jackson Laboratory, a biomedical research institution.
For the research, nearly 1,000 genetically distinct mice were assigned one of five diets:
- Eat any amount of food at any time
- Only consume 60% of their baseline calories each day
- Only consume 80% of their baseline calories each day
- Can’t eat one day each week, could chow down as much as they want the other days
- Can’t eat for two consecutive days each week, could scarf as much as they want the other days
The mice were given periodic blood tests as they were evaluated for the rest of their lives.
Mice on the unrestricted diet lived an average of 25 months while those on the intermittent fasting diets lived for about 28 months.
The mice that ate 80% of their baseline calories lived around 30 months while those that consumed 60% of baseline lived for 34 months.
Lifespan ranges varied within each group — for example, the mice that consumed the fewest calories lived anywhere from a few months to four and a half years.
The researchers determined that diets very low in calories generally extended the mice’s lifespan regardless of their amount of body fat or their blood glucose levels.
However, the study authors were surprised to see that the mice that lived the longest on the restrictive diets lost the least amount of weight — despite eating less.
Mice that lost the most weight on these diets tended to have low energy, weakened immune and reproductive systems and shorter lives.
“While caloric restriction is generally good for lifespan, our data show that losing weight on caloric restriction is actually bad for lifespan,” Churchill explained. “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.”
Churchill’s team pinpointed genetically encoded resilience as a key factor in lifespan, noting that the mice that naturally maintained their weight, body fat percentage and immune cell health even in the face of stress and caloric restriction, as well as the mice that did not lose body fat late in life, survived the longest.
Churchill said the results, published Wednesday in Nature, “suggest that a more moderate level of calorie restriction might be the way to balance long-term health and lifespan.”
The research team found that immune system health and traits related to red blood cells were more clearly linked to lifespan than weight, body fat percentages, blood glucose levels and body temperature.
Genetic features, yet to be identified, play a significant role in how diets affect a person’s health trajectory, the researchers said.
The study comes as intermittent fasting and extreme weight loss through weekly injections like Ozempic have become popular to stave off obesity and possibly slow aging.
Emily Feivor, a registered dietitian at Northwell Long Island Jewish Forest Hills Hospital, said more than one lifestyle intervention — not just healthy eating — is necessary for good health.
“Exercise and a balanced diet are arguably supreme when talking above improving overall health,” Feivor, who is not involved in the new research, told The Post. “Calorie restriction may not be for everyone as it could increase the risk for malnutrition and other health issues and should be discussed with your medical provider.”
