Here’s the story. Some wonks in a lab starved some yeast and found that the yeast seemed to live longer than well-fed yeast. “Hey!,” they said, “That must mean that if we starve mice, monkeys, and humans, they’ll live longer, too!”
Fast forward a few years and some other scientists tested the hypothesis in mice and rats and got…mixed results. Some rodents just wouldn’t live longer when fed less. In fact, some of them lived shorter (and hungrier) lives, which had the scientists scratching their heads. “Gee, there must be something wrong with these rodents. They’re supposed to live longer when underfed.”
So they found other breeds of rodents that behaved properly, and they ran some studies on those and found that, lo and behold, there are some rodents that live longer lives when fed less. And thus began the “life extension” craze of calorie restriction.
Next thing we know, there are websites and internet groups dedicated to supporting the practice of calorie restriction for humans. Of course, in a different context it would be called anorexia nervosa, but calorie restriction for life extension is different…because it’s for health. “Ah! Right. For health. Okay. Then it’s different. Not the same.” How’s it different? Well, sure, they are restricting calories, but they are doing it while maintaining “optimal nutrition.” So instead of being called anorexia nervosa it’s called CRON (calorie restriction with optimal nutrition) to sound very scientific and technically advanced (since it rhymes with TRON).
How does CRON work? Essentially, eat fewer calories. There are different approaches, but all involve eating fewer calories. Generally, it means eating a lot fewer calories. As in, many people report eating 1600, 1500, or even 1200 calories a day. (Some report eating as few as 800 calories a day, but the 1200+ figures are more reliable since they are reported by people who obsessively weigh and track every single bite they eat. But remember, they are healthy, not anorexic.)
To put this in perspective, during the landmark Minnesota Starvation Experiment a group of healthy young men were placed on a 1600 calorie a day diet for six months. The men became so physically and emotionally unwell (one of the men “accidentally” cut off his own hand) that the experiment is now considered to be unethical.
So what is different about CRON? Well, in most ways it’s not. Like the starving Minnesotans, CRONers are starving, but with a slightly different spin on things. CRONers generally eat lots of low calorie food, and many actually comment that they eat so much volume that they sometimes struggle to meet their (very low) calorie goals. So unlike the Minnesotans, CRONers often eat a lot of volume, which may produce feelings of fullness. CRONers also advise one another to focus on “nutrient-dense,” low-calorie vegetables and “superfoods” like nutritional yeast, kale, spinach, wheat germ, mushrooms, and non-fat dry milk. (Are you salivating yet?) They may also take supplemental vitamins and minerals to avoid deficiencies. So there are some subtle differences in typical CRON that result in less stomach growling and possibly fewer deficiencies in most nutrients. But they are still deficient in one key nutrient: calories.
A few years ago a paper was published in the journal Science reporting on the findings from a long-term starvation, er, I mean, calorie restriction study involving monkeys at the University of Wisconsin. The cheeseheads had two groups of rhesus monkeys: one group was the control group, the other was the intervention group. The control group was fed 20 percent more than the usual rhesus diet (anything sounding fishy yet?). The intervention group was fed 30 percent less than the control group. This is trickery designed to make it sound like the intervention group was eating 30 percent less than a normal diet, whereas, in fact, they were eating 16 percent less than a normal diet – still significant, of course, but not as dramatic as we’re supposed to think.
So in truth there were two intervention groups and no control. The first intervention group was the overfed group and the second intervention group was the moderately restricted group. The researchers reported that the restricted group had fewer deaths than the overfed group, which they concluded to mean that calorie restriction increases lifespan in primates, meaning that it might work in humans.
But wait a minute. Not so fast! Because what they forgot to mention was that a bunch of the starved monkeys did die. They died of accidents (remember the Minnesotan who chopped off his own hand), infections, and conditions other than the “acceptable” types of deaths such as death from cardiovascular disease. And when we consider the monkeys who died of all causes it turns out that there was no significant difference between the two groups.
Wait. There’s more. It turns out that the Wisconsin group’s lead researcher is one of the co-founders of LifeGen, which, according to its website, has several patents pending. You can bet that at least one of those patents will be more profitable if the public is convinced of the benefits of calorie restriction.
Fine, fine. Maybe it doesn’t work in monkeys, but that doesn’t mean it doesn’t work in humans, right? I mean, there have been lots of well-designed human trials showing that calorie restriction improves biomarkers of health in humans, right?
Well, actually yes, you’re right. There are a bunch of well-designed, clinical human trials that demonstrate that calorie restriction results in lowered LDL, triglycerides, blood pressure, and so forth. That sounds nice. But what rarely gets reported is that along with all the other reductions, the studies also report a reduction in metabolic rate and serum T3.
Strangely, in the calorie restriction studies, the researchers often speculate that perhaps lowered metabolic rate and lowered T3 levels may account for the life extension effects of calorie restriction in humans. Somehow they’ve forgotten that calorie restriction has never been shown to increase lifespan in humans.
But what about outside of calorie restriction studies? What do other researchers normally associate with lowered metabolic rate and lowered T3? Well, those folks over at LifeGen aren’t going to like this, but everyone else knows that lowered metabolic rate and lowered T3 are associated with starvation, malnutrition, and a whole bunch of disease states. In other words, they’re nothing to brag about.
If you don’t believe me, go ahead and look it up. Low T3 is called euthyroid sick syndrome. According to the Merck Manual, euthyroid sick syndrome is commonly seen as a result of fasting, starvation, protein-energy undernutrition, and anorexia nervosa, among other things. In other words, it’s not surprising that calorie restriction would have the effect.
And regarding lowered metabolic rate, those poor, starved Minnesotans had an average reduction in metabolic rate of 40 percent! Meanwhile, they were obsessing over food (kind of like CRONers weighing and measuring all their food), exhausted, depressed, anxious, impotent, and cutting off their own hands. So lowered metabolic rate doesn’t sound so great either.
Will calorie restriction make you live longer? All in all, it seems very unlikely. Clement Freud, the British chef, politician, and broadcaster (what a combo!) is quoted as having said, “If you give up smoking, drinking, and sex, you don’t actually live longer, it just seems longer.” Well, add calories to the list, too. And unlike smoking and drinking, despite what LifeGen and the breatharians would have you believe, you actually need calories.
So next time someone mentions the benefits of calorie restriction, remember: that stuff is for the…er…yeast? Meanwhile, eat long and prosper.