Calorie Restricted Mice Live 40% Longer. It Was Thought (Hoped) That This Could Be Extended To Human. Recent Research Says Otherwise.

A Silicon Valley billboard proclaims, “The First Person to Live 150 is Alive Today.” Prudential Life Insurance put up the sign, and it would certainly be a boon for their business were this to come true.

In pursuit of this objective, groups of people are practicing what is known as Calorie Restriction. These people take care to get sufficient nutrients and try to keep their caloric intake around 2000 or so calories per day. This is not in any sense starvation, but they would be considered thin, or on the thinner side of normal. This movement traces its roots to a long known fact: underfed lab mice live 40% longer. If such an increase would extend to humans as well, the first 150-year-old might well come from this crowd.

We can’t really experiment on humans, nor are we mice, but how about something a bit closer on the evolutionary ladder? Twenty-something years ago, two separate calorie restriction experiments were started with rhesus monkeys. The results are in, and frankly, it doesn’t look all that good for the calorie restrictors.

In the first experiment, some monkeys were fed all the Monkey Chow they wanted, and for the others, it was restricted. There was no difference in longevity for these two groups. In the second experiment, the calorie-restricted group was still fed restricted amounts of Monkey Chow, and that group did outlive the control group, but the control group wasn’t fed Monkey Chow. The control group was fed a simulated American diet. Not exactly apples to apples here. What this mainly proves is that Monkey Chow is better for you than the American diet, but we probably already knew that. What’s also proven, though, is that calorie restriction didn’t improve longevity for groups fed the same sort of food, and this bodes poorly for the hopes of the calorie restrictors.

More to the point, as you will recall from the YOUR WATE AND FATE section, those with an overweight Body Mass Index had lower all-cause mortality than a normal BMI, a surprising result. There are also results for thin BMI available and they do even worse than normal or overweight.

The main objection we have to calorie restricting is that it places the body into catabolic mode way too much of the time, plus it isn’t much fun.

Note that the human version of the “experiment” will eventually be completed. Many calorie restrictors will continue in spite of the monkey trial results and time will tell. We hope they prove us wrong, but that’s not where the research is currently pointing.

Why did this work for mice and not for the monkeys? If you look at life expectancy versus weight for mammals, it’s two years for mice and 25 years for a moose. That moose

could weigh 400 pounds. This sort of “more weight means greater longevity” trend applies to all mammals with two exceptions: bats, in a class by themselves; and primates, which are all the monkeys, the apes, and ourselves (actually we are also apes, but that bothers some people). Specifically, our 10-pound rhesus monkeys will beat the 400-pound moose, living up to 30 years (depending on whether they get Monkey Chow or an American diet). A chimp, weighing in at around 100 pounds, might live 60 years. (Cheetah, from the “30”s Tarzan films, only recently died, purportedly at age 80, but this may not be credible.)

We live longer still, 122 years being the current record. In all three cases we are way off the chart. We are living a lot longer than the standard “mammal weight-longevity” trend. There are a lot of reasons for this and it is almost surely the case that we have already “evolved” whatever was needed to get that extra 40% the starving mice got. We are basically already there. We really don’t know where that 150-year-old is going to come from.

PS An aside: I (Dr. Mike) have a corny aphorism: “Starvation cures disease.” You may have seen me use this phrase before and there is an important kernel of truth in it. I have seen remarkable improvement in health in patients that, always for very, very serious reasons, have undertaken prolonged fasts. That said, and note this carefully(!), over time and in most patients I cumulatively have seen only harm. The harm being everywhere from an acceleration of a serious underlying disease to simple rebound over-eating. In sum: eat well, eat wisely, but eat!