長生きの鍵はカロリー摂取量より空腹の時間、マウス研究

【パリＡＦＰ＝時事】餌の量を減らすだけでなく、与える回数を減らすことで、マウスの健康を向上させ、生存期間を延ばす効果がみられたとする研究論文が１８日、発表された。（写真は資料写真）
　科学誌「ネイチャー・メタボリズム」に掲載された論文によると、１日当たりの摂取カロリーと給餌回数を変えた結果、カロリーと回数を減らしたマウスは、通常通りに餌を与えたマウスよりも、生存期間が約半年延びた。
　給餌が１日に１回だけのマウスには優れた代謝適応も見られた。
　米ウィスコンシン大学のダドリー・ラミング氏率いる研究チームは、マウスを複数のグループに分けて研究を行った。それぞれのグループに異なる量と回数の餌を与え、通常の餌を無制限で食べることができた対照群と比較した。
　このうちの二つのグループは、１日当たりの摂取カロリーが通常よりも３０％低くなるよう餌の調整が行われた。片方のグループには低カロリーの餌が与えられ、終日好きなだけ食べることができた。もう一方のグループは、通常カロリーの餌を食べることができたが、給餌回数は１日１回に限定され、空腹の時間が２１時間設けられた。
　研究によると、２１時間の空腹を強いられたマウスは、対照群のマウスと比べて、約半年長く生きた。
　一方、低カロリーの餌を終日食べられたマウスは、対照群のマウスよりも若干短命だった。摂取カロリーを抑えたにもかかわらずだ。
　ラミング氏は、カロリー制限の効果を得るには、空腹の時間を設けることが重要だと言う。
　さらに別のグループには、対照群のマウスと同量の餌を３時間で食べさせ、その後１日の空腹期間を設けた。
　摂取カロリーを減らさず空腹の期間を設けたこのグループは、摂取カロリーを抑えつつ空腹時間を設けたグループと同程度の健康効果が示された。ただ、生存期間については比較できていない。
　ラミング氏は「（両グループとも）血糖値の調整と代謝適応に優れていた」と説明する。
　人の場合はどうだろうか。ラミング氏は、人が食べ物の摂取を１日のうち４～８時間の枠内に制限することについて、短期的な研究では「一定の効果があるように思える」とした。ただ、長期的な影響についてはまだよく分かっていないとしている。【翻訳編集ＡＦＰＢＢＮｅｗｓ】

〔ＡＦＰ＝時事〕（2021/10/20-12:36）

Eating less often does more to improve the health and lifespan of rodents than simply eating less, a study said Monday.
Researchers looking at mice on different diets found those who were fed fewer calories in a single daily feeding lived longer than mice eating the same number of calories distributed throughout the day.
The study, published in Nature Metabolism, showed mice who ate only once a day also demonstrated improved metabolism.
Study author Dudley Lamming of the University of Wisconsin told AFP that scientists have known for about a century that restricting calories extends the lifespan of rodents.
But previous studies on mice and calorie restriction had included unintentional fasting with mice typically fed just once a day.
Lamming's team decided to find out whether the timing between feedings might play a role -- and discovered it was not the quantity of food alone that mattered.
Instead, calorie restricted diets ensure that mice are fasted for much of the day ? and that imposed fasting-period (when we eat) is critical for the benefits of calorie restriction to life and health.
Lamming's team put mice on different diets, with a control group getting unlimited access to regular food.
Two other groups had calories restricted by 30 percent, one with access to low-calorie food all day and the other receiving a 30 percent smaller amount of regular food in a single feeding with a 21-hour fast.
The study shows that mice on a calorie restricted diet with 21 hours between meals lived about half a year longer than mice who ate as much as they wanted at any time of day.
Mice with constant access to a low-calorie diet, on the other hand, lived lightly shorter lives than the control group, even though they consumed fewer calories.
The imposed fasting period is essential for the benefits of a calorie restricted diet, Lamming said.
A final group of mice was trained to eat a similar amount of food as the control but in a three-hour period followed by a long daily fast.
- Humans? Not so fast -
Though their longevity was not measured, the mice in the last group -- which fasted without reducing calorie intake -- showed just as many health benefits as the group that ate fewer calories and fasted.
(Both groups) are better able to regulate their blood sugar and to better adapt their metabolism to different demands during the course of the day, Lamming said.
Mice on a low-calorie diet who ate throughout the day meanwhile did not show benefits such as better blood sugar control, improved strength in old age and longer life.
Diets that include intermittent fasting are popular among celebrities from Hugh Jackman to Kourtney Kardashian.
But Lamming points out that while short-term studies on humans seem to confirm that restricting food intake to a four- to eight-hour window in the day seems to have some benefits, the long-term consequences remain unknown.
We still don?t know the best time of day to fast, if different people might respond to fasting or time-restricted feeding differently, he added.
Reacting to the findings, Stephen O'Rahilly, Director of the MRC Metabolic Diseases Unit at the University of Cambridge, said they would be hard to apply to humans given the huge differences in the speeds at which the two species process foods.
A comparable human experiment would need to have humans eat all the calories they need for a week in a single day and then starve for the next 6 days, he said.
As mice live about 2 years and we now live to around 80, we might have to do the study for more than 50 years to test whether such a massive change to our eating habits actually benefited human longevity, he added.
Lamming noted one possible takeaway for our species: people already cutting their daily calorie count by 20 or 30 percent may want to consider limiting the time frame for eating those meals.
If our findings apply to people, they may be losing some of the benefits of calorie restriction by spreading out their meals throughout the day, he said.