My current take on calorie restriction

Calorie restriction is one of the most studied longevity interventions in the lab. It is also, in my opinion, the most overrated when you try to translate it to actual humans. I have been asked about CR roughly once a month for the last fifteen years, and my view has hardened over time. Here is the practical version.

Reason one: almost nobody will do it

The most recent CDC data put roughly 70 percent of American adults in the overweight or obese category. We cannot get the country to ideal body weight on calorie maintenance. The proposal to take a clinically normal person and have them eat 20 to 30 percent below their needs for life is a non-starter for almost everyone. That does not make it wrong. It makes it irrelevant to almost everyone reading this.

Food is one of the main entertainments people have. Cell phone apps, cable channels nobody watches, social networks where nobody actually meets in person, those compete with food for time and attention but rarely beat it. If you ask me to bet on a behavior change, I will not bet on chronic CR.

Reason two: our ancestors were not calorie restricted

The nutritional anthropology is reasonably clear. Paleolithic populations were not CR. They were intermittently lean, occasionally feasting, and generally consuming more total calories per day than modern sedentary Americans, just from much more nutrient-dense whole foods. They also spent most of their waking hours engaged in obtaining and processing food. The argument that we are evolutionarily wired for chronic caloric deficit is hard to support.

Reason three: the most calorie-restricted human populations are not the healthiest

The most chronically underfed group in our society is the frail elderly. Caloric and protein supplementation in this population is associated with better outcomes, not worse. The other globally underfed populations are not the long-lived ones either. CR enthusiasts often skip past that.

Reason four: the primate data is more complicated than you have been told

Two long-running rhesus monkey studies, one at the University of Wisconsin and one at the National Institute on Aging, both followed CR for decades. The Wisconsin study found a modest extension of healthspan and lifespan. The NIA study did not. The difference, on reanalysis, came down to control-arm diet quality, not CR per se. If you look at the photos of the famously restricted Canto and the non-restricted Owen, you see two very different behaviors. Anyone who watched those videos and chose to be the restricted monkey was, in my opinion, not paying close attention.

Reason five: the rodent data is about maximum lifespan, not mean lifespan

In mice, CR shifts the maximum lifespan tail. The oldest mouse in a CR colony tends to live longer than the oldest mouse in a fed colony. The average mouse does not necessarily do better. That is a meaningful distinction the marketing version of this story leaves out.

The CR-sirtuin-telomere link

CR is mechanistically tied to the sirtuin pathway, p53, and PPAR gamma. I have called these cellular gatekeepers in my own writing. The more recent work suggests these pathways sit downstream of telomere length and function, not the other way around. In other words, whatever metabolic benefit CR confers, focusing on telomere maintenance may capture more of it with less suffering. Telomerase activation, in the animal studies, produces something CR alone has not produced, which is true biologic age reversal in measurable terms.

What I actually do

I run a roughly Paleo pattern most of the time. Nutrient-dense, low-glycemic, high-quality protein, plenty of plants, moderate calories per meal. The total intake is lower than what most Americans eat, but it is not CR. I do not weigh my food. I do not track macros. I eat until I am satisfied, stop, and go back to work.

If we ever develop a true CR mimetic that activates the same pathways without the deprivation, I will be the first to try it. Resveratrol and pterostilbene are not it. Whatever it ends up being, it will probably do less than people hope and more than skeptics expect. That is how most of this work goes.

No diet has been studied with rigorous human longevity as the endpoint. Given the difficulties, none probably ever will be. Until that changes, the best we can do is eat in a way that produces good biomarkers, good function, and a life worth living.

— Doc