Can you reverse your biological age?

You can move the markers. Small trials have shifted DNA clocks with diet, exercise and eating less, and your fitness age moves every time your fitness does. Nobody has shown yet that turning back a clock adds years to a life, so judge a habit by what it does for your health.

Why “reverse your age” sells

The promise is easy to sell. You take a test, follow a plan, take the test again and watch the number drop. A lower number feels like proof that you’ve bought time. But a clock is a measurement of aging, and changing the measurement doesn’t automatically change the thing it measures.

The simple version

A clock is like a thermometer. Treating an infection brings a fever down. Holding the thermometer under cold water also brings the number down, and it does nothing for the infection. A test result only means something if the change came from the body getting healthier.

What the trials have shown

An 8-week program. In a 2021 pilot trial, 43 healthy men aged 50 to 72 followed a plan of diet, sleep, exercise and relaxation, plus probiotics and plant supplements, or had no program. The program group’s DNA age on a saliva test came out 3.23 years younger than the control group’s. Within the program group, the drop from the start was 1.96 years, and that was too small to rule out chance. It’s an interesting result, but it was a small group, one clock and eight weeks.

Two years of eating less. In the CALERIE trial, 220 healthy adults who weren’t obese were assigned to eat 25% fewer calories or eat as usual for two years. Eating less slowed one measure, DunedinPACE, by a small amount. Two well-known clocks, PhenoAge and GrimAge, didn’t change. The researchers said that a real test of whether slowing aging adds healthy years would need long trials measuring disease and death.

Why one result can mislead

The same blood sample run twice through six popular DNA clocks gave answers up to 9 years apart, from lab noise alone. A 3-year drop on one test can be smaller than the test’s own wobble.

What does move

Fitness moves, and in 122,007 treadmill tests it predicted survival as strongly as smoking or diabetes did. People who were inactive most of their adult lives but got active in their 40s and 50s had the same lower risk of dying as people active all along, in a study of 315,059 Americans. That result is about survival itself, which is what a clock tries to estimate.