What’s more important to you – your left arm or your right foot? What would you rather keep if you had to lose one or the other?

It’s a stupid question I know. Because both are independently useful and important. Yet I’m asked a very similar question all the time. What’s more important diet or exercise?

The answer is, of course, both are. Yet exercise often gets marginalised as the poor cousin to diet. “You can’t outrun a poor diet”, meaning you can’t exercise enough to get out of having to eat healthy.

I agree you can’t. But this sort of discussion forces a head to head comparison with two very important (but different) healthy behaviours.  I find the “what’s more important diet or exercise” completely ridiculous. Here are two independent health behaviours, both of which give you loads of benefit if you do them right. To me, it’s a bit like asking what you consider more important your left hand or our right foot?  I’m sure you’d say both are pretty important, and you’d prefer both of them, wouldn’t you? They are after all, independently useful.

We’ve even invented special terms to marginalise those who want to keep fit. “He’s a real fitness freak”.

So what’s freakish about fitness?

What’s freakish is just how independently important fitness is for us.

The field of physical activity/exercise and health really started in the 1950s when English epidemiologist Prof Jerry Morris noticed that the bus drivers had almost twice the chance of a heart attack as the bus conductors on London buses. The only real difference between the two groups was how much they moved each day.

Since then the field has exploded into a huge science of activity and exercise and how it affects our health. A milestone was the US Surgeon General’s office offering specific advice around the evidence in the mid 1990’s.

Nowadays we have two competing messages. The “low bar” from public health –  do anything – hopefully 30 minutes most days.  That’s pretty different from the fitness industry where high intensity vigorous exercise is what you do, the “high bar”. That’s hard stuff, and to be sure there’s merit in both messages. But I want to make the case that we should be talking more about cardiorespiratory fitness – or just being fit as the common ground for us all.

I want to argue for fitness because that is the measure where the best evidence exists for the benefit.
I want to see the word fitness, re-enter the language of modern medicine.

Fitness is medicine, prevention is cure

There’s been lots of work, much of it by Prof Steve Blair at the Cooper Centre, Dallas Texas, looking at cardio-respiratory fitness. Blair has shown that in the cohorts of fit versus unfit people coming through his clinic the benefits of being fit are massive reductions in the chances of dying of anything (all-cause mortality) as well as the usual things like cancer, heart disease, stroke, and dementia.  Not only that, but when you are alive your life is much better with increases in the quality of life, well-being, and less disability. 

Being high in cardio-respiratory fitness is one of the single most important factors in health, wellbeing, and longevity.

The study by Chakravarty et al, (2008) tells a big story of the sorts of effect you might expect. They followed a group of 538 members of a nationwide running club and 423 healthy (matched for baseline health) controls from Northern California aged 50 years and older beginning in 1984. (Find the study here https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3175643/).

In the 21-year follow up study the results were astonishing.

The differences were stark:

  • 34% of non-runners were dead, but only 15% of the runners had died. As shown in the survival curve below (Figure 1).
  • The runners had much less disability. Disability set in later, was less severe and progressed more slowly. As shown is the disability progression graph (Figure 2).

Figure 1: Survival curves at the 21 year follow-up for runners (only 15% dead) v non-runners (34% dead).

Figure 2: Survival curves at the 21 year follow-up for runners v non-runners.
The runners reached the same level of disability almost 13 years later.

So how much aerobic (cardio) were both groups doing? Quite a lot.

At baseline line runners were averaging a whopping 311 minutes a week of vigorous exercise (mostly running), and the non-runners were still doing 87 min/week of activity. At the 21-year follow up the runners were still averaging 287 min/week, while control non-runners were up to 138 min/week. I’m assuming the non-runners were higher at the follow up because the most sedentary ones had died off pushing the average up.

This study, with all the limitations of the observational study, shows the sheer magnitude of the effect of largish amounts of cardio. Nothing else in modern medicine comes close to being this good.

But we aren’t talking about 30 min of walking a few days a week, are we? We are talking about an average of 5 hours of cardio a week.

I reckon this is about the minimum activity humans used to get into for most of the 200,000 years we’ve been on the planet. I can’t do that research study of course. But that’s my hypothesis. Hunter-gatherers spent many hours each day hunting, gathering, walking, hiking, scouting, foraging, wandering, and generally being active at a low level of intensity. They enjoyed wide-ranging benefits from this active lifestyle, including enhanced fat metabolism, cardiovascular function, brain development, stress management, and general health and longevity.