BlogNovember 6, 20268 min read

Does exercise protect your sense of smell as you age?

Pedro RodriguesFounder of Actus
Bruna GüntherFounder of Actus

In a 5-year randomized trial of adults aged 70 to 77, followed for 10 years, neither high-intensity interval training (HIIT) nor moderate continuous training slowed the normal decline in smell compared with a control group. What did matter was fitness: people with a higher VO2peak (peak oxygen uptake, a lab measure of aerobic fitness) had better smell scores at 10 years. For older lifters, the takeaway is to build aerobic fitness, whatever the cardio style.

What did the study do?

Reitlo and colleagues published this trial in Frontiers in Physiology in 2026 (Reitlo et al. 2026). It asked whether years of structured exercise protect odor identification, which is the ability to name a smell. Smell tends to fade with age, and it is linked to brain health, so it is a useful early signal to track.

Item	Detail
Who	Older adults aged 70 to 77
Design	Randomized controlled trial with three groups
Groups	HIIT, moderate-intensity continuous training (MICT) or a control group asked to follow national activity guidelines
Intervention length	5 years
Follow-up	Testing at baseline and after 1, 3, 5 and 10 years
Main sample	A longitudinal group of 106 participants
Extra sample at 10 years	326 more participants, giving a cross-sectional group of 388
Smell test	Sniffin' Sticks, a standard pen-based odor test
Other measures	VO2peak, brain MRI (including hippocampal volume) and self-reported exercise habits

The researchers used two lenses. The first followed the same people over time to see whether the exercise groups lost smell more slowly. The second compared a larger group at the 10-year mark to see whether group or fitness explained smell scores at that point. They also ran sensitivity analyses to check whether dropouts or selection bias changed the picture.

What did it find?

Smell declined in everyone. Odor identification dropped significantly over time, and the drop was the same in the HIIT, MICT and control groups across the 10 years. Assignment to an exercise program, on its own, did not protect smell.
Fitness did not separate the groups either. There were no significant group differences in VO2peak over time. This matters for reading result 1: if the groups ended up with similar fitness, it is hard for the training label to show an effect.
Fitter people smelled better. Higher VO2peak at baseline and at 10 years was linked to better odor identification at 10 years. The authors read this as a direct link between aerobic fitness and less age-related smell loss.
Brain structure lined up with smell. A larger hippocampus, a brain region tied to memory, was linked to better smell scores at the 10-year follow-up.
How long you train beat how hard you train, for a while. Self-reported exercise intensity was not linked to smell. Self-reported exercise duration was linked to smell up to the 3-year follow-up, but not after that.

The plain reading: the program you are assigned to matters less than the fitness you actually carry. In this group, being fit went with a better sense of smell, whatever the route to that fitness.

How does this compare with earlier evidence?

There are no prior reviews on exercise and smell to compare against here, so the comparison is about the fitness side of the story. That is where the new trial is surprising.

Several reviews find that HIIT raises aerobic fitness in older adults. A 2025 meta-analysis of 87 randomized trials with 4,213 older adults found that HIIT raised VO2max by a mean of 2.46 mL/kg/min (Men et al. 2025, Front Endocrinol). A 2021 meta-analysis in older adults found HIIT beat MICT for VO2peak, with a weighted mean difference of 1.74 (95% CI 0.80 to 2.69). It also found programs longer than 12 weeks worked better (Wu et al. 2021, Exp Gerontol).

The broadest summary agrees. An umbrella review of 24 meta-analyses, covering 429 primary studies, found HIIT raised fitness more than MICT, with mean differences of 0.52 to 3.76 mL/kg/min. That held across groups that included older adults (Poon et al. 2024, Scand J Med Sci Sports). Earlier, a review of 65 intervention studies found HIIT raised VO2max in both normal-weight and overweight adults (Batacan et al. 2016, Br J Sports Med). In adults aged 18 to 45, a meta-analysis of 29 trials found HIIT similar to or better than MICT for fitness (Guo et al. 2023, Int J Environ Res Public Health).

So the new trial does not contradict the idea that fitness matters. It extends it to a new outcome, smell, through the fitness link. What stands out is that the HIIT group did not end up fitter than the others over the long run, unlike the shorter trials in those reviews. One plausible reason is that the control group was told to follow activity guidelines, so many of them likely stayed active too. That would shrink any gap between groups.

What are the limits?

The fitness link is an association. The link between VO2peak and smell comes from comparing people, not from the random assignment. Fitter people may differ in other ways, such as health or habits, that also protect smell.
Small long-term sample. The group followed over time had 106 people, which is small for detecting differences in a slow outcome over 10 years.
Most of the 10-year data is cross-sectional. The 326 people added at 10 years were measured once, so they show differences between people, not change within a person.
An active control group. Because the control group followed national activity guidelines, the trial compares exercise programs with fairly active people, not with sitting still.
Self-report. Exercise intensity and duration were self-reported, which is less precise than measured training.
One population. All participants were in their 70s at the start. The results may not apply to younger lifters.

What should you do with it?

Older lifters: treat aerobic fitness as its own goal. Higher VO2peak went with better smell at 10 years, so add regular cardio alongside your lifting rather than relying on strength work alone.
Pick the cardio style you will keep doing. HIIT and MICT gave the same smell result in this trial, and the groups did not differ in fitness over time. Long-run consistency is what moves VO2peak.
Time-poor trainees: HIIT is a fair option for fitness, not a shortcut for smell. Reviews show HIIT raises fitness at least as well as MICT, but this trial found no extra smell benefit from the HIIT program itself.
Beginners: think in years. Self-reported exercise time was linked to smell only up to the 3-year mark, and the fitness link showed up at 10 years. Any protective effect builds slowly.

Can exercise bring back a sense of smell you have lost?

This trial did not test that. It studied healthy older adults whose smell declined slowly with age, not people who lost smell suddenly from illness. If you notice a sudden change in smell, that is a reason to see a physician, not a training question.

Is HIIT better than steady cardio for brain health?

Not in this study. Smell, used here as one marker of brain health, declined the same way in the HIIT, MICT and control groups. The reviews above show HIIT can raise fitness a bit more in shorter trials, and fitness is what tracked with smell. Either style can work if it raises your fitness.

Why would fitness affect your sense of smell?

The study does not prove a mechanism. It found that higher VO2peak and a larger hippocampus were both linked to better smell scores. That fits the idea that good blood flow and a healthy brain support smell, but the trial was not designed to show cause and effect.

Sources

This brief was drafted with AI from the sources listed above and passed automated source checks before publishing. Pedro Rodrigues, founder of Actus, is the responsible author.

Educational content, not medical advice. Training and diet changes carry risk; stop if you feel pain and talk to a physician before changing your program.