Calorie Restriction Does Not Promote Longevity??
So there I was yesterday, enjoying my day and skimming the headlines on Twitter…when one in particular caught my eye.
Calorie Restriction Doesn’t Prolong Life
I could almost hear the collective voices of all the anti-aging proponents saying “What??!!”.
After all, the biggest benefit touted for a CR (Calorie Restriction) lifestyle was “longevity”. Now they say it’s not all that true?
This quickly became a hotly talked about topic online and many questions arose…so I dropped everything, started reading up on the multiple articles and now attempt to logically lay out what I found.
Say It Ain’t So!
The news of this shocking research conclusion came straight from the National Institute of Aging:
Scientists have found that calorie restriction—a diet comprised of approximately 30 percent fewer calories but with the same nutrients of a standard diet—does not extend years of life or reduce age-related deaths in a 23-year study of rhesus monkeys. However, calorie restriction did extend certain aspects of health.
Unlike a previous study on CR in monkeys that showed longevity benefits, this latest study seemed to have found no longevity advantage for the CR group (but did find it some health benefits including reduced cancer risks). Not exactly the outcome the researchers and CR community expected!
But maybe this really isn’t the first time this has happened.
In fact it seems that with some more digging, not all CR animal studies are positive. (Note we lack human studies because we just don’t have any long term data for humans…we live too darn long)
Calorie Restriction vs Healthy Weight
There seems to be one big difference between the 2 CR longevity studies on monkeys with opposing results. The first (older) one compared a CR group to a control that ate ad libitum (as much as they wanted). The second was stricter with a CR group and control group that ate specific maintenance levels.
The end results seem to be the control group from the first experiment were more overweight (and had worse health), while the second control group seemed to be stable at a “healthy” weight.
Ricki Colman, a co-author of the first monkey study and an associate scientist at the Wisconsin National Primate Research Center, believes that the differences may reflect variance in the diets given to the animals in the two studies.
“They may be modeling different things,” she says, explaining that in her study, the control animals were allowed to eat freely while in the new research, both controls and those on the restricted diet were limited to specific maximum amounts.
Her control animals, she says, may reflect more of a typical American diet, while the controls in the new research are more like people who already eat healthy amounts.
Colman’s Wisconsin study diet also contained far more sugar— 29% of calories, compared to 4% in the NIA trial. In fact, 40% of control animals in the Wisconsin study developed diabetes, but none of the restricted monkeys did, despite their sugary meals.
What I take from these findings is that when comparing a CR to an overweight control group, there are more obvious health (and therefore longevity) benefits.
However comparing a CR to an already healthy weight control group, there are less dramatic health improvements (which influences longevity).
So in a pursuit for longevity, you may already be doing well if you eat good foods and maintain a healthy weight. This new information may mean that extreme CR (30-40% less maintenance) full time may not provide any real advantage…unless there is something else at work too.
Is it About Protein?
Another article posed an interesting observation as well about protein intake being a key factor in longevity.
Fontana pointed out that key hormonal changes found in both calorie-restricted mice and humans were not detected in either group of monkeys, an absence that he blames on their relatively high-protein diets.
In humans, those hormones decrease only when protein intake is dramatically reduced. It’s not enough to cut calories alone. “It’s possible that we don’t see some of the beneficial effects of longevity in these monkeys because they were on a high-protein diet,” Fontana said.
“The old idea is that a calorie is a calorie. When you restrict it, you have a beneficial effect. Our data and other data suggests this isn’t the case. The quality of the diet matters,” Fontana continued.
Except from Wired’s Experimental Low-Calorie Diet Gets Puzzling Results in Monkeys
I’m going to guess that “hormone” they speak of is IGF-1 (insulin-like growth factor-1) which has been identified as a major contributor to the aging process in many organisms.
What is interesting though is that in even some CR studies, IGF-1 was not lowered when protein intake was not restricted. However compare to a more restricted protein group (or fasting) and you have greater reductions of IGF-1 overall.
Calorie restriction (CR) decreases serum IGF-1 concentration by ~40%, protects against cancer and slows aging in rodents. However, the long-term effects of CR with adequate nutrition on circulating IGF-1 levels in humans are unknown. Here we report data from two long-term CR studies (1 and 6 years) showing that severe CR without malnutrition did not change IGF-1 and IGF-1:IGFBP-3 ratio levels in humans.
In contrast, total and free IGF-1 concentrations were significantly lower in moderately protein-restricted individuals. Reducing protein intake from an average of 1.67 g kg of body weight per day to 0.95 g kg of body weight per day for 3 weeks in six volunteers practicing CR resulted in a reduction in serum IGF-1 from 194 ng mL to 152 ng mL.
Excerpt from “Long-term effects of calorie or protein restriction on serum IGF-1 and IGFBP-3 concentration in humans“; Luigi Fontana et al; Aging Cell. 2008
So it seems unlike rodents, humans also have to restrict protein if they want the added longevity benefits that may stem from a lower IGF-1 environment. This could also be the same reason for the diminished longevity benefit of CR seen in the more recent monkey study.
Hopefully it hasn’t been all that confusing, but I’m going to wrap up my final thoughts on all this.
- Overall I would say this study is not “throwing out the baby with the bathwater” on CR just yet, but helping us to understand more of how it works.
- There were differences in each of the experiments to consider including macronutrient %s, type of foods, older experiment had higher levels of sugar, difference in control group weights, and more.
- CR group in the older monkey study seemed to fare better than the ad libitum (as much as they wanted) group, which lead them to also become overweight.
- CR group in the latest monkey study seem to have similar longevity benefit as the group kept at a maintenance level (did not gain additional weight).
- If protein was higher in the CR group for the latest study, that may explain the reason longevity was not impacted as IGF-1 may not have been significantly lowered.
- CR (full time) is not to be confused with “intermittent” CR or fasting, which has been shown to have numerous health benefits.
- If looking for longevity, having a lean (but not starvation-like) weight along with intermittent protein restriction of some sort may be the new focus (IGF-1 lowering). Exercise can also play a role too.
Even though there is still much unknown, it is studies like this that do allow us to get more insight into what can work for health and longevity.
I don’t think many of you would be shocked to hear that eating better foods and maintaining a leaner body weight does improve your health. Outside of that, longevity in cultures is still a multifaceted equation that can vary from type of foods eaten to stress and quality of life.
In the end I’m not about to jump on the CR (full time) bandwagon in hopes of living a few more years. Eating 30-40% of my daily maintenance, being hungry all the time and end up 130lbs at 6’1″ is not my goal.
However using “intermittent” fasting and/or condensed feeding windows, I believe is still a simple way to lose weight/maintain a lean body and still potentially get health benefits (lower glucose/insulin, lower inflammation, increased stress-response defenses) without the pain of full time CR.
If we could give every individual the right amount of nourishment and exercise, not too little and not too much, we would have found the safest way to health. ~ Hippocrates
Find out what the "IF Life" is all about and learn why your fears about not eating all day may actually be keeping you from getting the results you are after. Just enter email below and click on "Get Access Now" button for the free PDF to be sent to you.