Minus 25 Prozent Kalorien für ein langes und gesundes Leben?

Das NYTimes-Magazin berichtet ausführlich von einer zweijährigen Studie, die den Effekt einer 25%igen Kalorienreduktion in normalgewichtigen Menschen untersucht. Studien an Ratten hatten schon lange den faszinierenden Befund ergeben, dass reduzierte Kalorienzufuhr das Leben deutlich verlängern könnte, wobei die Übertragbarkeit auf Menschen fraglich war.

Der erste interessante Punkt ist der Unterschied zwischen dem Altern selbst und Krankheiten, die im Alter zunehmen:

Instead, Calerie is investigating how (and if) a spartan diet affects the aging process and its associated diseases. To the Calerie researchers, these are quite distinct. The aging process, which researchers sometimes call “primary” or “intrinsic” aging, refers to the damage that ordinarily accumulates in our cells as we grow older, a natural condition that seems to have limited the maximal lifespan of humans to 120 years. Diseases that accompany the aging process — often called “secondary aging” — are those afflictions increasingly prevalent in the elderly, like cancer, diabetes and cardiovascular disease.

Überraschend auch, dass körperliche Betätigung trotz aller unbestrittenen gesundheitsförderlichen Eigenschaften nicht so starke Effekte zu haben scheint wie die Kalorienreduktion:

In a study on rats, he compared animals that were lean because of exercise with those that were equally lean from calorie restriction. “Both had an increase in average life span,” Fontana said, but only calorie restriction was able to slow down aging and increase maximal life span. That suggested that “leanness” was not in and of itself determining the rate of aging. “Speaking of humans,” Fontana added, “if you are lean because you are exercising, of course you are doing good, because you’re preventing types of diabetes, some kinds of cardiovascular disease and maybe some types of cancers. But the data suggest that calorie restriction is more powerful. And the people on C.R. are more powerfully protected from diseases than the exercisers.”

Das macht Sinn vor dem Hintergrund der (natürlich evolutionären) Erklärungsansätze, die auch klar machen, warum man tatsächlich in den untergewichtigen Bereich gehen muss, um die vollen Vorteile zu erfahren:

The effects of calorie restriction may simply be an evolutionary legacy, “a metabolic, hormonal and molecular adaptation” to a world of sparse resources, as Luigi Fontana, one doctor in charge of the Washington University trial who also holds a position at the National Institute of Health in Italy, described it to me. By slowing aging and increasing resistance to disease during periods of food scarcity, the adaptive responses to fewer calories increased the odds that animals and humans that lived short lives might survive until they could reproduce. In laboratory settings, calorie restriction seems to “work” — that is, it seems to influence primary and secondary aging — when the diet of an animal of normal weight is curtailed by a significant percentage. The degree of calorie restriction can’t exceed 50 percent, which is when laboratory animals begin to die. Until that point, however, the more severe the calorie-restriction regimen, the greater the health benefit — a lifespan 50 percent again as long in studies on mice and rats. These results might not apply to the overweight. As Fontana told me, moving a heavyset person’s body-mass index from, say, 35 to 29 might increase his longevity by reducing the risk for diseases like diabetes. Yet it is not “triggering the anti-aging pathways” that have been observed at the cellular and molecular levels in animals of normal weight when placed on a calorie-restricted diet.

Zusammen mit weniger kontrollierten Beobachtungen an Mitgliedern von Niedrig-Kalorien-Vereinen (was es alles gibt!) und über längere Zeiträume ähnliche Ergebnisse bringen ist das in ziemlich starker Punkt. Bleibt die Frage, wie praktikabel das alles ist. Und auch hier eine Überraschung: Mehr als gedacht. Nicht einmal die beteiligten Forscher selbst erwarten, dass viele der Versuchsteilnehmer die reduzierte Diät weitermachen. Diesen scheint es aber mehrheitlich sehr gut zu gefallen:

As it happened, I ran into several participants in St. Louis who were in the homestretch. None planned on an ice-cream binge. Instead, they told me, they would continue with their diets while looking forward to estimating, rather than counting, their calories. “I’ll probably do that for a week or two,” Josh McMichael told me. About a month later, in late September, I sent McMichael a note to see how he was faring. He gained eight pounds in the weeks after finishing, he said, but later shed most of that weight. “I tried the new massive burgers from Burger King,” he said. “Twice. Wasn’t worth the side effects.”

Then he added: “I think I’ve gotten over things like that. For the most part.”

Da überrascht es mich wenig, dass die Zusammenstellung der Nahrung, die eine solche Reduktion der Kalorien bei gleichzeitigem Wohlbefinden möglich macht, ziemlich genau das ist, was ich ohnehin gerne esse:

Subjects willing to re-engineer their eating habits appear to have an easier time on the diet. When I asked Susan Roberts, who runs the Tufts study, if there was a danger in Americans trying calorie restriction on their own, without a dedicated team of medical experts offering advice, she suggested that there are built-in safety mechanisms. Roberts said she didn’t think anyone would be successful by reducing portion size. “If you don’t change your diet to a high-satiety diet, you will be hungry, and you will fail,” she told me. A high-satiety diet, she said, was bound to be a healthful diet with a lot of vegetables, fruits and insoluble fiber — the kind found in some breakfast cereals, like Fiber One — that her research indicates has a unique effect in helping calorie-restriction subjects feel fuller, probably because they activate certain receptors in the lower intestine.

Datum: Mittwoch, 14. Oktober 2009 0:04
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