Calorie restriction, or CR, may be one of the easiest ways to extend the lives of many animals in the lab, but as for humans? We’re not sure.
Making sense of the information right now
The fact different animals have wildly different lifespans is telling. Humans survive for a long time with an atrocious diet and a sedentary lifestyle, even if they generally experience negative effects. Your average couch potato will still outlive any dog by far; even if said dog does daily yoga and eats plenty of kale.
A large study of human calorie restriction has now released its results, and they’re uncertain. Scientists weren’t measuring life extension itself, but they did want to see if humans exhibit similar short term metabolic benefits from calorie restriction- which other animals do. 218 individuals were studied, and when they reduced 25% of their calorie intake, cardiovascular disease risk decreased and insulin sensitivity went up. This is good news, but they failed to show substantial changes in metabolic rate or body temperature, which other organisms have done.
“People in the study lost weight with calorie restriction, but we didn’t see the same changes that we see in animals. That could mean that calorie restriction doesn’t work the same way in people as it does in animals, or it could mean that other changes linked to calorie restriction are the ones affecting longevity. Whatever those beneficial changes are, we’d like to identify them and see whether there’s some way to help people get those benefits without having to cut calorie intake so dramatically.”
So what can we interpret? Well, some of the participants were unable to reduce their calorie intake as intensely, so reliability is a problem. When calorie restriction has been applied to animals effectively, it also began earlier in life – suggesting applying CR earlier has more potent effects. The whole thing really displays how confusing metabolism is however, and how much we’re essentially guessing at the moment.
“As we continue to try to unlock the mechanisms that make calorie-restricted animals live longer, we are certain that eating smaller portions of healthier food is a good idea for all of us, but cutting intake by 25 percent is very difficult for most people. In the meantime, we do know that exercise and maintaining a healthy weight and diet can contribute to healthy aging.”
This variation shows that organisms have evolved different genes, and these impact on their maximum lifespan. Let’s be clear here, calorie restriction has had fantastic effects on a number of creatures, but it’s not magical and doesn’t work on every creature – like the housefly. Humans actually have a comparatively long lifespan, and there’s a chance we’ve already tinkered with some of the pathways and networks that provide longevity to animals in the lab. We don’t have enough information at this point to make a conclusion.
Getting to the point
We know eating moderately and healthily – namely lots of vegetables and not overdoing it – can help keep you healthier as you age. It looks like it might well lower the risk of multiple age-related diseases, and in that sense it’s a great idea. The question is does it live up to people’s expectations and hopes?
Calorie restriction, if combined with sufficient nutrition, probably has multiple benefits, but whether they’re better than a more generous healthy diet remains to be seen. We don’t know if it can extend lifespan yet, but from what we know right now we can make a few sensible guesses:
Calorie restriction improves various biomarkers and can help keep you healthy (as long as you get all the micro-nutrients you need), but it may be no more effective than a moderate, healthy diet.
CR likely helps increase healthspan, but perhaps not lifespan. I.e. it might help you reach 90 but probably won’t get you to 150.
Effects on smaller organisms can’t be easily extrapolated to humans: doubling the lifespan of a mouse does not mean we could expect to reach 200 years old on CR.
If you’re really serious about life extension, then CR might help you live longer in a better condition, but we’re going to need something more potent for substantial anti-aging effects
Intermittent fasting may be as effective as long term CR
With more analysis, CR mimetics like metformin – namely molecules which mimic the positive effects – could be equally as effective. Having a really bad diet would be counter-productive, but it might mean you don’t have to limit your intake quite so much if these drugs are available
Read more at Futurity