I’ve decided to go alcohol-free this month. Not for any particular reason – I’m not raising money for a worthy cause, although if you need a reason that’s a good one – I just like to lay off the booze for a few months each year. Sometimes it’s because I’m training for an event, other times it’s just to prove (to myself) that I can. Admittedly, in my case it’s hardly a huge sacrifice, considering I average about two or three drinks a month anyway. But for some, going without alcohol for a month – let alone several months a year – seems crazy.

I wasn’t always so restrained when it came to alcohol. In my early twenties I could drink with the best of them – and it showed, in my puffy face and my chubby body. But somewhere along the way I decided alcohol wasn’t doing me any favours. Apart from the extra kilos I was carrying, it made me feel crappy the next day (now there’s a shocker) and robbed me of my motivation to exercise. Now 10 years and two kids later I’m fitter and healthier – not to mention 10 kilos or so lighter – than I was in my early 20s. And I think alcohol – or the lack of it – is a big reason why.

Ironically, in those binge-drinking days I was more fastidious about what I ate than I am now, but would think nothing of downing eight or 10 drinks – often more – on a night out.

What is it about alcohol that fools us into thinking the kilojoules in it don’t count, or somehow aren’t as fattening as those in food? Now as a trainer, I regularly come across women – and men – with the same mind set, wondering why they can’t shift those extra kilos.

But if you compare the kilojoules in alcoholic drinks with the sorts of foods that anyone watching their weight wouldn’t touch with a 10-foot pole, the reality is pretty sobering (so to speak).

Take what I consider to be your pretty typical woman in her 30s or 40s. She sits down at night following a hard day at work or chasing after kids, and pours herself a glass of wine to unwind. A standard drink of wine is 100ml but most wine glasses comfortably hold about 150ml – the equivalent of 1.5 standard drinks. There’s 425 kilojoules right there – the energy equivalent of a Caramello Koala.

Then, after dinner she might pour herself another. It’s only two drinks, right? Not exactly what you’d call a big night. Well, actually it’s three standard drinks, and it’s also about 850 kilojoules – roughly the same as two big scoops of vanilla ice cream or a smallish serving of pasta –  and that’s before you’ve even eaten anything.

On its own it might not seem like a lot but over an average week (or on one or two big nights out), you could easily drink the kilojoule equivalent of a one-litre tub of ice cream or a family-size block of chocolate… Makes you think twice, doesn’t it?

Even if you’re a “moderate” drinker, who has only a couple of glasses most weeknights plus a few lazy drinks on the weekend, all of a sudden you’re looking at an extra 5000 kilojoules or so a week – that’s more than half a day’s worth of food for the average woman. And over the course of a year, it adds up to a whopping extra 260,000 kilojoules…

To put this in perspective, a kilogram of fat contains about 37,000 kilojoules. So if your alcohol consumption is anything like the example I used above – and let’s be honest, many people drink much more than that each week – then just by cutting out alcohol you could potentially lose almost a kilogram of fat every seven weeks, or about seven kilos of fat a year.

On that basis, if you lose the booze for just two months a year, you could shed a kilo of fat. That’s without changing anything else about your lifestyle. Combine that with a healthier diet and more exercise and – thanks, Captain Obvious – the results will come much sooner. I’m not saying you need to become a teetotaller – where’s the fun in that? But cutting down what you drink is a pretty easy way of shedding a few extra kilos without much effort. All of a sudden a month off the booze isn’t sounding so crazy after all…