Science, Starbucks and Slimming

By Wendy Sadler

It’s the new year, so almost everyone seems to be slimming and watching their weight, or in fact hoping to watch their weight disappear. In the SMS offices we have a whole range of techniques being employed to build a healthier team with everything from Becky’s triathlon training to James and David’s tried and tested fruit diet!

Me? I’m opting for the ‘scientifically proven’ (!) 5:2 fasting programme plus the target of reaching 10,000 steps a day. But how can science help keep us motivated? Personally I’m very motivated by visual and kinaesthetic or tactile messages, so I’ve worked out a way to use my science knowledge of density to help keep me going through the calorie-poor days ahead. I’m calling it:


Catchy isn’t it?! The idea is this. I want to be able to visualise and feel the weight I am losing to help me realise how much easier life could be without carrying it around. I worked out that I’d like to lose about 9kg (almost 1.5 stones) so I started to think what that weight would feel like. Now here’s where the science bit comes in (concentrate!). Density is a measure of how much mass (stuff) something has per volume (the space it takes up). Water has a density of 1kg per Litre (in fact this is linked to how we first defined what a gram is – but that’s another story). What do we see around us that comes in 2 Litre bottles? Fizzy drinks. If I need to lose 9kg, that’s equivalent to over four 2 Litre bottles worth of liquid. Imagine how heavy it is to carry four 2L bottles of drink home from the shops, then think of someone offering to carry them for you. This gave me a Eureka moment of motivation. If I achieve my goal, it will be like handing over 4 big bottles of drink and not having to carry them any more! 4 bottles of 2L drinks

How can I visualise my progress? Easy. Get four empty 2L bottles and gradually fill them according to the weight you lose. Now you can not just see how much you have achieved but actually feel what carrying the extra weight was like.

People often talk about the fact that muscle weighs more than fat but this isn’t strictly true. Human muscle is more dense than fat, so muscle of the same weight takes up less room in your body and makes you smaller. Human fat weighs about 0.9g per cubic cm and a cubic cm of water is a bit heavier at 1g. So in fact if I filled my bottles with human fat up to the 9kg target it would take a bit more bottle space – but it’s near enough for this purpose! (You can see what comparative weights of fat and muscle look like here if you’re feeling brave.)

But what does this have to do with Starbucks? Well this week I stumbled upon a Starbucks store being assessed by what I assume was the Starbucks quality control police. The guy was taking all sorts of measurements of the drinks and noting what temperature they were at. Then he pulled out the tiniest little cup-sized digital scales and started weighing the drinks! Why should the weight of the drinks matter? Well, not only does it equate to the amount of stock they are selling but more importantly (I am guessing) to the density of the drink, especially when consuming frothy latte’s which (let’s be honest) contain quite a lot of air. You want just the right amount of air in there to get the texture of the drink right without customers feeling they are just paying for a lot of froth. So by knowing the volume of the drinks:

Tall (aka small!) = 350ml

Grande (aka medium) = 470ml

Venti (aka large) = 590ml

…and how much they weigh, they can check every Starbucks drinks is served at exactly the right density! And incidentally, if you are a Starbucks addict on a diet, you might want to check out their guide to drinks and snacks under 500 calories!

I’ve done a week so far and lost 1.8kg – which looks a bit like this. Follow the rest of my progress on twitter

Weight loss in a bottle

Visual image of the weight-loss so far. But unlike a graph, I can pick it up and feel it!


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Posted in Exploring Science, Physics
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