Why eating less may slow aging

Alex Eben Meyer

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Calorie restriction, or consuming fewer calories without causing malnutrition, has long intrigued scientists studying longevity. In other species, such as mice and rhesus monkeys, reducing calorie intake has been linked to longer lifespans. But extreme dieting can also come with drawbacks, including weakened immunity and impaired healthy aging. 

A new Yale study published in Nature Aging offers insight into how restricting calories may slow aging without negatively affecting overall health. Led by Vishwa Deep Dixit, a professor of pathology and immunobiology and director of the Yale Center for Research on Aging, researchers analyzed plasma samples from 42 individuals who reduced their caloric intake by an average of 14 percent over a two-year period. Among more than 7,000 proteins examined, some declined significantly following calorie restriction, including an immune-related protein called complement component 3a (C3a). This protein plays an important role in inflammation, which scientists increasingly believe contributes to aging. 

The team confirmed the finding in mice, showing that levels increased with age. Typically, immune complement proteins are produced by the liver. But as co–first author Manish Mishra, a postdoc,  explains, “It’s not the liver, it’s the visceral white adipose tissue” that is the site of elevated C3a production. This type of fat was an unexpected production source. Importantly, these findings did not appear to depend entirely on weight loss. While participants lost an average of 17 pounds, researchers found no clear relationship between body mass index and reductions in some inflammatory proteins, such as C3a. 

While researchers caution that calorie restriction may not guarantee a long life, these findings suggest that some biological processes associated with aging may be more adaptable than thought. Co–first author Hee-Hoon Kim, a postdoc, recommends “calorie restriction, especially for older adults, should be done together with exercise to maintain lean muscle.”