Previously in posts 2 and 3, we talked about the blind spot for many when it comes to weight loss, adaptive thermogenesis, which is a naturally occurring feedback mechanism existing in humans and animals to reduce weight changes, and is clinically significant for keeping the weight off. We also mentioned that it would be helpful to get your resting metabolic rate (RMR) measured if you have previously lost weight, and mathematical modelling could also help you remove some guess work when it comes to planning.
What activity goal should you consider for weight loss?
Your physical activity is the only part of energy expenditure (EE) in your voluntary control. It accounts for about 20% of total energy expenditure (TEE) if you are inactive (e.g. commute in cars, sedentary work, no much exercise - sounds familiar?) or over 50% of TEE if you play in a competitive sports league, or compete in Tour de France.
For many, walking is a practical and fun way to change our sedentary lifestyle and increase EE. You have probably heard of the 10,000 steps a day goal. In this post. We will talk about where it came from and how much energy cost this means to you.
1. Where does the 10,000 steps/day value come from?
When a health-related convention gains widespread acceptance, the underlying premise may no longer be questioned. If the assumptions are overlooked, the convention may be misused and the results may be problematic.
Here is the story of 10,000 steps/day slogan. In 1965, a Japanese manufacturer of industrial instruments and special watches, Yamasa Tokei, developed and the launched the first commercial pedometer. It is a smart-looking gadget that snuggly fits onto your waist and comes at ¥2,200 each, a slightly upmarket price at the time, considering the average salary of a school teacher was less than ¥40,000 a month [1].
The product was named Manpo-kei (万歩計 in character or まんぽけい in kana), which literally translates into “10,000 steps meter”, and successfully gained popularity in the Japanese market in the commercial campaign.
The “10,000 steps a day” slogan was initially embraced by the walking clubs in Japan, before it gained popularity in wider communities. In fact, the notion of using pedometer was later endorsed by the Japanese Ministry of Health and Public Welfare. In 1998, they specifically set out a national goal of increasing baseline values (7200 steps/day for women and 8200 steps/day for men in 1998) by 1000 steps as part of the Health Nippon 21 Objectives.
Nowadays, it is inevitable to encounter “10,000 steps a day” slogan in the cyberspace, as google returns over quarter of a million hits (265,000 at the time the post is written), and someone is talking about it nearly everywhere on the planet.
The timeline of Yamasa Tokei mentioning Manpo-kei:
Lots of interesting commercial posters for the legendary Manpo-kei here:
2. How much does 10,000 steps/day mean to you?
The claim 10,000 steps/day was supported by Dr. Yoshiro Hatano who studied typical steps per day of various lifestyles during the 1960’s. It was established that 10,000 steps/day translated to approximately 300 kcal/day (or 5 MET/h) for an average middle-aged Japanese man. But how much does that mean to you in terms of calories and lifestyle changes?
The answer is it depends on your basal metabolic rate, how much you weigh, your stride length, how fast you walk and where you walk.
For the sake of simplicity, assume a stride length of 0.75m (i.e. 30 inches for an average man), and you walk on a level surface, it is easy to figure out the time it takes to complete 10,000 steps at different paces (the Time column in the table).
Let's also assume a basal metabolic rate (BMR) at 1kcal/kg/h (i.e. 3.5ml oxygen/kg/min, a value previously thought to be representative for a 40-year old male in good shape and had been widely used as the standard man - we will cover this topic later).
Metabolic equivalent (MET) is a measure of the average energy cost for a physical activity, typically expressed in kcal/kg/h. An intense activity is associated with a high value. MET values are measured and curated by scientists around the globe and are published as The Compendium of Physical Activities.
MET x Time x 70kg gives the energy cost in kcal for a 70kg man.
As you can see, the energy varies with your pace. Dr. Hatano made his estimate at a brisk pace of 120 steps/min, which is equivalent to 3.4mph or 5.4km/h in our case. In our calculation, this costs around 400 kcal.
It might look a bit more than the 300 kcal estimate Dr. Hatano had, perhaps because an average middle-aged Japanese man in the 60’s weight much less than70kg. On the other hand, if a sedentary lifestyle index of <5,000 steps/day is considered (it is still controversial where the line should be draw exactly), what 10,000 total steps really mean is >5,000 steps above and beyond sedentary lifestyle. The difference it makes is perhaps ~300 kcal for the said person.
Now, you have some ideas about where 10,000 steps/day comes from and what it means roughly to you.
Next week, we will look at the effectiveness and feasibility of 10,000 steps/day. We will ask whether this is the right target for you, and critically if there are any better targets you can use to change and monitor your lifestyle.
It is going to get a lot more interesting and useful for you so stay tuned!
References: