Thursday, July 09, 2015

Alasdair Wilkins lost 45 kg in weight by walking.

The headline to a story I read was "How Alasdair Wilkins lost 45kg just by walking".

www.news.com.au/lifestyle/fitness/how-alasdair-wilkins-lost-45kg-just-by-walking/story-fnlsuulf-1227434091460

The problem with this type of article is it is very misleading to people and then people wonder why they can't lose weight.

Here's the problem. This article emphasises walking only and quotes "Basically, I just went to the gym and I walked. On a treadmill, uphill, at a brisk pace, for about an hour every day — and I do mean every day". It is only down further in the article there's a one line sentence "Alasdair wrote that he didn’t adjust his diet — just ate smaller portions." He didn't adjust his diet. Yes he did. He dieted as well. That is what eating smaller portions is.

Let's look at the maths behind what Alasdair Wilkins did. Alasdair initially weighed 285 pounds (129.5 kg). He walked for one hour per day for a year. That's 365 hours or 21,900 minutes. The Energy Exercise Calculator (www.justlocal.com.au/clients/dieting/exercise.php) enables us to calculate how much energy we use for particular exercises given a weight and the time taken. However since Alasdair's weight changes over time so does the energy used. To help us estimate we'll use his average weight for the period which is 129.5 kg less half of 45 kg giving us 107 kg. We now enter 107 kg, a time of 21,900 minutes, select fast walking (7 km/h) and that gives us energy usage of  768.895 kJ. If we divide this by 33,000 (the energy equivalent of 1 kg of fat) we get an expected weight loss of around 23 kg.

That's roughly half the weight that Alasdair lost. How was the remaining weight lost? It was those smaller portions. Half of the weight loss was from exercise and half from dieting, even though Alasdair didn't think he was dieting.

If Alasdair had simply continued to eat at his usual level, which was more than his body needed, there's a good chance he may not have lost any weight at all. Only when his energy intake comes below what his body requires would we expect to see a reduction in weight. At roughly 2,000 kJs per day for fast walking, it is very easy to counter the exercise with food or drinks.

Alasdair's story is a great story and I think it is inspiring. It shows if you increase your exercise and reduce your energy intake you can achieve a massive result. Keep in mind Alasdair did this seven days a week. You can't expect the same result doing it just 2 or 3 days a week.

I've tested losing weight by dieting alone (this worked very well), exercise alone (this didn't work), so my next test will be to diet and exercise using an approach similar to Alasdair's by doing one hour of walking per day, along with a 2,000 kJ reduction in energy intake. I'll share the results on my site www.WeightLossMaths.com.au. I provide links to all my weight-loss calculators on that page as well as on JustLocal.

Kelvin Eldridge
www.JustLocal.com.au

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