Yale School of Medicine researchers, publishing in Nature Aging, found that cutting daily calorie intake by roughly 11 to 14 percent for two years significantly lowered blood levels of an immune protein called complement component 3, or C3, that helps drive the chronic, low-grade inflammation linked to aging and age-related disease.
In aged mice, blocking C3 directly reduced this inflammation, pointing to a possible drug target that could mimic parts of the calorie-restriction effect without asking people to eat less every day for years.
What 14% fewer calories looks like
On a 2,000-calorie diet, a 14 percent cut works out to about 280 fewer calories a day, roughly the amount in a large bagel or a couple of glasses of soda.
Participants in the underlying CALERIE trial, funded by the National Institutes of Health, achieved that reduction over two years without going hungry and lost about 18 pounds on average, according to Yale School of Medicine.
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The Yale team analyzed plasma from 42 CALERIE participants and screened more than 7,000 proteins.
One stood out. C3, part of the immune system's complement cascade that helps the body fight infection, dropped sharply after calorie restriction.
Why C3 matters for aging
Chronic, smoldering inflammation that builds up with age, sometimes called inflammaging, is now considered a shared engine behind heart disease, type 2 diabetes, dementia and frailty.
C3 sits at the center of that process. It activates immune cells that quietly damage tissue over decades even when there is no infection to fight.
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Digging into where the extra C3 was coming from, the researchers traced it to immune cells inside belly fat, not the liver as textbooks would predict.
"We were not expecting that because these proteins are mainly synthesized in the liver," said Manish Mishra, one of the study's lead authors, in the Yale announcement.
That location matters, because it suggests the benefit is tied to how calorie restriction reshapes fat tissue, not simply to the pounds lost.
"This suggests that calorie restriction has a beneficial effect that is unique to adipose tissues and is likely independent of weight loss," co-author Hee-Hoon Kim said in the same release.
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A possible shortcut in mice
The bigger prize is a drug that could deliver some of the same benefit.
When the researchers gave aged mice a compound that blocked C3 activation, age-related inflammation eased, Yale reports.
The team is now looking at whether existing C3 inhibitors already approved for other conditions might be repurposed for aging-related inflammation.
Senior author Vishwa Deep Dixit framed the ambition carefully.
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What it means for readers now
The findings do not amount to a prescription.
The human data come from 42 volunteers in a tightly supervised trial, and the mouse work is early.
Anyone considering a sustained cut in calories, especially older adults or people with a chronic condition, should talk to their doctor before making a change, since long-term calorie restriction can affect bone density, muscle mass and nutrient intake.
Still, the size of the shift is worth noting.
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Participants did not fast, did not follow an extreme diet, and did not skip meals.
A modest, sustained trim was enough to move a biological marker that scientists have linked to how the body ages at the cellular level.
For now, the strongest practical read is the same one cardiologists and dietitians have offered for years.
Trimming portions modestly, favoring whole foods over ultra-processed ones, and keeping added sugar and alcohol in check are habits already tied to lower inflammation in large observational studies.
The new work adds a plausible mechanism for why even a small reduction may pay off decades later.
The next step, Dixit's team says, is testing whether C3-blocking drugs already on pharmacy shelves for rare immune conditions can safely dial down inflammaging in older adults. That trial has not begun.
This article is made and published by Ida-Marie Palm Varbæk, who may have used AI in the preparation.