THE ARISING · Longevity & Healthspan
Higher Cellular Recycling Linked to Worse Physical Fitness in Adults Over 70
Autophagy, the body's cell-cleaning process, is widely assumed to decline with age, and more of it is often presumed to mean healthier aging. A new human study suggests the picture is less simple: in adults over 70, higher autophagy activity went along with worse physical function.
The work was published in the journal Aging Cell in 2026 by a team led by Caroline Kumsta at Sanford Burnham Prebys. It is an observational study of human cells taken from healthy volunteers, plus a very small exercise pilot. It shows links, not cause and effect.
Autophagy is the process cells use to break down damaged proteins and other waste so the parts can be reused. Many scientists have called its decline a hallmark of aging. The authors note that most evidence for a decline comes from model organisms and post-mortem tissue, and that direct evidence across human cell types is limited.
The team used cells from the San Diego Nathan Shock Center Clinical Cohort, whose members reported being free of chronic disease. They studied skin cells called fibroblasts (44 donors), neurons converted from those skin cells in the lab (22 donors), and freshly isolated white blood cells. They measured both gene activity and autophagy flux, the actual rate of recycling. Flux is measured by blocking the cell's disposal step and seeing how much material builds up.
Gene activity and real activity did not match. Autophagy-related genes were more active with age in skin cells and, to a lesser extent, in the lab-made neurons. But the measured flux did not follow. Flux fell with age in skin cells from men, stayed stable in skin cells from women, and rose in neurons from women. In blood cells, flux grew more variable with age and trended higher in older people of both sexes. The authors also found that counting visible autophagy structures in cells did not track flux.
The central finding concerns physical function. The link between autophagy flux and physical function varied across the adult lifespan. But in adults over 70, higher flux was associated with reduced physical function, in all three cell types. According to the ScienceDaily coverage of the work, higher flux in blood cells went with lower aerobic fitness, in skin cells with higher body mass index, and in the neurons with weaker grip strength, lower metabolism and a higher resting heart rate.
The authors interpret this cautiously. Elevated flux in older adults may reflect a compensatory response to age-related stress, rather than a stronger cleanup capacity. That is an interpretation, not something the study proved. "It appears that increased autophagy flux may be good in younger people yet problematic in older people," Kumsta said, according to ScienceDaily.
The study also included a pilot. Per the paper, blood-cell flux dropped after 12 weeks of mild exercise, while physical function improved. ScienceDaily reports that this involved five people aged 77 to 88. With so few participants and no comparison group described, the result is a hint worth testing, not evidence that exercise works through this route.
For you
For personal health, the practical lesson is about caution. The study did not test fasting, supplements or any drug that raises autophagy. It cannot say whether such approaches help or harm. It does cast doubt on the assumption that pushing autophagy up is always a good sign, especially in later life. Lead author Tatiana Moreno told ScienceDaily that people inferring autophagy from gene activity "need to be really careful about their interpretations."
Other limits matter. The samples came from healthy volunteers at one point in time, so the study cannot show how any one person's autophagy changes over the years. Sex differences were found in some cell types, but the authors note that sample sizes were limited for some analyses.
What to watch next
Larger, controlled exercise trials that track autophagy flux alongside fitness, and studies that follow the same older adults over time to learn whether high flux is a warning sign or a response to stress.
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