Despite what it says, there have been about saeven gadzillion studies over the last 10 years making the same kind of claim. They tend to bug me for a number of reasons:
- The headlines tend to obscure the dose response: sure 4K or 6K or whatever steps may be enough to reduce mortality risk by a chunk, but it still leaves a lot on the table and if you walk more, risk will reduce further.
- Anyway, if you die, that's that. I'm much more interested in avoiding debilitating stroke, heart attack, cancer and you generally need a lot more exercise to make a big dent in the risks for these.
- The actual situation depends hugely onwhat you're doing when you're not walking those steps: schlobbing on the couch or doing something active like gardening or a physical job or whatever. Once again the headlines are just misleading.
IMO the best basis for deciding how much exercise is enough is still the old FAO/WHO guidance from 20 years ago:
https://www.fao.org/3/y5686e/y5686e.pdf Which is consistent with more recent large-scale metastudies showing that you need a bunch more exercise than 4K stes per day if you want to reduce risks as far as possible.
The core recommendation is for a "Physical Activity Level" (PAL) of at least 1.75. This is the calories you burn per day (TEE), divided by your basal metabolic rate (BMR), the amount of calories you would burn in a day if you were in a coma (more or less).
If you have a fitbit or similar it will give you an estimate of your TEE. You can use this
https://www.calculator.net/bmr-calculator.html for an estimate of your BMR.
I nerded out and worked up the table below showing how much walking you need to add to an otherwise essentially sedentary life (like mine) to achieve a PAL of 1.75, depending on your average walking cadence.
| Walking | | Walking |
| Steps / min | METs | KSteps / day | Hours / day |
| 100 | 3.0 | 34 | 5.7 |
| 105 | 3.5 | 27 | 4.3 |
| 110 | 4.0 | 22 | 3.4 |
| 115 | 4.5 | 19 | 2.8 |
| 120 | 5.0 | 17 | 2.4 |
| 125 | 5.5 | 16 | 2.1 |
| 130 | 6.0 | 15 | 1.9 |
| 135 | 6.5 | 14 | 1.7 |
| 140 | 7.0 | 13 | 1.5 |
You need to walk a lot! I walk at about 125 steps/minute on average, and to achieve a PAL of 1.75 I need to walk about 16K steps a day, which means walking for about 130 minutes per day.
This is obviously way more than the "at least150 minutes per week of moderate to vigorous" exercise you see in more well-known patient-focused guidelines.
As with the 4K or 6K or whatever steps per day claims, these common guidelines are directed towards taking out a chunk of risk, but they still leave a significant amount on the table for people who are otherwise sedentary. Further, they stem from original studies which assumed a somewhat active, rather than a sedentary background lifestyle. There are also nanny-issues and just the inertia of having a dubious message so widespread & well-known. But I wish more adequate, nuanced and adequate guidelines were more readily available.
As a nerd notes, the table uses estimates from studies by Tudor-Locke for relating cadence to METs. MET = "metabolic equivalent of task" and it's a measure of energy burn intensity intended to be independent of sex, age, body size etc. Energy expenditure/time = BMR/time x average METs.
Eg: My BMR by the standard estimate in the link above is about 1,470 kcal which corresponds conveniently to 1 kcal per minute. In a coma, energy burn rate is 1 MET = (for me) 1 kcal per minute. Walking at 125 steps/minute corresponds to about 5.5 METs (from Tudor-Locke's studies), which for me means burning about 5.5 kcal per minute.
My fitbit (and presumably similar devices) calculates calorie burn by a process equivalent to estimating METs and multiplying this by BMR as calculated by the same formula as in the link. It estimates METs mainly from its measurement of heart rate, using a some calculation simialr to (but I think not exactly the same as) an approximation reasonably common in the literature: METs = (Heart Rate/Resting Heart Rate) x 6 - 5.
www.theguardian.com
