Eating High Nutrient, Ultra-Low Calorie (CRON) Diets as a Path to Life Extension

by Nils Osmar. April 5, 2022

Lab animals that are fed diets rich in nutrients but low in calories tend to have unusually long lives. Some believe that people who eat that kind of diet could too.

I’m not talking here about doing intermittent fasting, or about “dieting” or “cutting calories” for a few days or weeks in the commonly understood sense. People who practice Caloric Restriction with Optimal Nutrition (the CRON diet) have made the decision to eat a diet which is low in calories but extremely high in nutrients, not for a day, week or month, but — if they decide to stick with the plan — for the rest of their lives.

How it Works

Lab animals that are switched from “normal” diets to calorie-restricted diets have been found to live much longer than their litter-mates who are free to eat as much as they want whenever they feel like it. It’s not unusual for the calorie-restricted animals to live almost twice as long as their litter-mates. (For a human being, this would move the marker from around 80 years, to around 160 years.)

To be clear, extrapolating from animal studies to what the results would be in humans is speculative. It would take longer than a typical human lifespan to find out whether following the CRON diet (or any other intervention) really extends life by that great of a degree. But some people have made a decision to try doing so. People who engage in CRON dieting as a permanent lifestyle are called “Cronies”. There are about 100,000 Cronies in the world today, all of who have decided to permanently lower their calories in the hopes of achieving extended lifespans in a state of great health.

Some of them do look dramatically younger than their chronological ages. The man in the video below is an example. He’s 55, or was at the time the video was taken, and had been following the diet for two decades when the interview was filmed.

Note that caloric restriction is not (necessarily) the same thing as fasting. CR slows down the metabolism; fasting speeds it up. People who practice CR as a permanent lifestyle should not fast, or vise versa. Combining these approaches by eating a diet chronically low in food energy, then taking long breaks from eating any food at all, could result in severe nutrient deprivation and a shorter, not longer, lifespan.

Possible Drawbacks

CRON diets tend to suppress mTOR. Low mTOR activation is associated with greater longevity, but it can have a compromising effect on immune function. This could leave people more vulnerable to succumbing to a variety of diseases. (Lab animals put on CRON diets are protected by the conditions of their lives from exposure to pathogens; human beings, who don’t live sheltered lives in a laboratory setting, are not.)
People on the CRON diet sometimes report feeling cold much of the time and having a loss of libido.
Some of the highest nutrient foods (such as fats, including oleic acid, DHA and EPA from fish oil) are also high in calories. On the CRON diet, these fats need to be kept low. This could have unforeseen negative consequences.

Personal Note

I thought at one point in my life about doing caloric restriction, but opted against it so because of evidence suggesting that fasting works just as well, and has a much more minimal impact on a person’s life. Fasting is a form of calorie restriction, as your calories will tend to come in lower over the long haul if you fast regularly. I’m currently doing a form of alternate day fasting three days a week (eating one meal a day on those three days. When you average my calories out over time, they’re about 20% lower than they would be if I weren’t doing ADF.)

Committing to the CRON diet means that you always – every day – eat a set number of calories, and count and measure every meal to make sure. Fasting’s easier; you can eat what you want on non-fasting days, then take breaks from eating on your fasting days. This results in lower calories overall, without having to count and measure every day.

Or Just Raise Your Ketones?

One additional approach, according to this study, would be to focus instead on increasing ketone production, because ketones mimic the life-extending properties of caloric restriction. Ketones can be increased by:

Fasting (particularly fasting for 24-36 hours)
Eating a low-carbohydrate diet or ketogenic diet
Eating fats such as MCT oil
Eating a cyclical ketogenic diet (cycling in and out of ketosis) (For example, cycling between eating a ketogenic diet and eating a Mediterranean diet)
Taking exogenous ketones