What actually ages you, in order

Most of us think we already know what's good and bad for us. Don't smoke. Move more. Sleep well. So a tool that tells you smoking is bad can feel a little pointless. You knew that.

But there is a different question, and it is the one that turns out to matter: not what is bad for you, but how much, and in what order. When researchers actually measured which everyday things track with faster biological aging, across nearly half a million people, the ranking was not the one most of us carry in our heads. Two of the strongest signals were things almost no health app asks about, and that most of us would never think to mention to a doctor.

They are: how tired you feel, and how much you look forward to things.

Where these numbers come from

This isn't a wellness hunch. It comes from a 2025 study in Nature Medicine that used the UK Biobank, a British research cohort of 492,567 people followed for years. The researchers tested 164 different environmental and lifestyle exposures and narrowed them to 25 that independently predict both earlier death and faster aging, even after accounting for the others.

They measured "aging" two ways, which is what makes it trustworthy. The first is mortality: over years of follow-up, who died, and what predicted it. The second is a proteomic age gap, built from the 45,441 participants who also gave a deep blood sample. A model learns to guess your age from the pattern of proteins in your blood, and the gap between that protein-predicted age and your real age is a physical readout of how fast your body is actually aging. When a factor shows up on both measures, pointing the same direction, you can believe it.

One more finding, because it reframes everything: in this study, your environment and how you live explained far more about how long you live than your genes did. Roughly 16 to 19 percentage points of mortality risk came from these exposures. Genetics contributed only 2 to 3. So much of your health is written by how and where you live, not only by your DNA.

The order, and the surprise

Here are the everyday, changeable factors, ranked by how strongly they tracked with dying sooner. The number is the mortality hazard ratio: how many times higher the risk was for people at the high end of each factor. The proteomic aging clock agreed with this ordering.

1. Feeling tired or low on energy, most days. Risk about 1.8 times higher.
2. Rarely feeling interest or enthusiasm (what clinicians call anhedonia). About 1.75 times.
3. Financial hardship. About 1.5 times.
4. Sleeping too much or too little (both ends age you; seven to nine hours is the calm middle). About 1.4 times.
5. Smoking, measured as lifetime pack-years. About 1.3 times.
6. Being physically active, which runs the other way and protects you. Regular activity lowered risk by roughly a quarter to a third, the single largest protective lever here.

Read that order again. The persistent sense of being worn out, and the quiet fading of interest in things, both outranked smoking. Financial stress outranked it too. And movement did more good than smoking did harm.

One key note so this is not misread: that fifth-place finish for smoking is the effect of an average smoking history. A current heavy smoker compared with someone who never smoked carried close to three times the mortality risk, one of the largest effects in the whole dataset. Smoking is not safe. The point is not that cigarettes are fine. The point is that things we treat as background noise, like exhaustion and low mood, are carrying huge weight we've largely been ignoring.

The very biggest signals of all were things you can't change overnight on a Tuesday: your body size as a child, whether you grew up with economic security, whether you have work. Those matter enormously, and they deserve their own conversation. But this piece is about the levers still in your hands.

What "tired" and "unenthusiastic" actually mean here

People tend to balk at these two. Aren't they just moods? How can a survey question predict how fast you age?

They're not vague. They're two of the most validated questions in medicine. In the study, each person answered, about the previous two weeks:

How often have you felt tired or had little energy?

How often have you had little interest or pleasure in doing things?

with four choices, from "not at all" to "nearly every day."

If those sound familiar, it is because they are almost word for word two of the core items on the PHQ, the depression screener used in doctors' offices around the world. The second one, little interest or pleasure, is the clinical definition of anhedonia, the flattening of things that used to feel good. These are a standardized instrument, asked the same way of nearly half a million people, not random soft questions.

And it's biologically reasonable that they track aging. Persistent low energy and lost enthusiasm sit downstream of the same things that wear a body down over time: chronic stress and its hormones, poor or broken sleep, low-grade inflammation, under-treated depression, and often a physical illness that has not been named yet. The body keeping score of all of that can show up first as simply feeling tired and flat.

This is a signal, not scolding

Some of the reason these two rank so high is what scientists call reverse causation. Sometimes you feel exhausted and joyless because something is physically wrong that has not been diagnosed yet. The tiredness is not a character flaw or a failure to optimize. It can be the earliest visible edge of something worth catching.

That's exactly why we treat it as a signal rather than a verdict. Mauka will never tell you to simply cheer up and add a year to your life. What the data supports is more useful: if you have been running on empty or the color has drained out of things for weeks, that's one of the strongest signals in the entire dataset. It's worth taking seriously, worth mentioning to someone, and worth looking into. Naming it is the first step to acting on it.

Why we ask

If the largest and most careful study of aging we have asks people how tired and how interested in life they feel, and finds that the answers rival smoking, then a health system that never asks is not being polite. It's looking away from one of the strongest signals it could see.

Most longevity products chase inputs easy to count or comfortable to show: steps, macros, the newest supplement. They tend to skip the things that are strongest but least glamorous, the ones that are a little uncomfortable to bring up. We would rather ask the real questions, weigh them against everything else in your life, and at minimum be able to tell you the truth: this one is a serious signal, and here is where it sits among everything shaping your healthspan.

Almost all of these factors can change, and that's why Mauka exists. You can't rewrite your childhood, but exhaustion, sleep, movement, and the slow return of enthusiasm are things we can bend in life, especially once someone names them out loud and shows you they matter.