Full disclosure: as I write this I’m eating a brownie.

In the last few weeks the UK has been covered in posters of women sweating in a spin class, bouncing at Zumba and jiggling as they run up a hill. The This Girl Can campaign is everywhere, encouraging women to get their sprint on and take up more exercise. But should we be moving our bodies for reasons beyond a government mandate? Could it actually help us at work?

Certainly all the traditional wisdom says it could. We’re all familiar with the saying, “healthy body, healthy mind.” We know we feel better after a bit of exercise and at the end of last year a study of over 8,000 school children found that those with a regular diet of junk food performed less well at school. So, this week I set out to discover whether a healthy lifestyle can actually make you better at work.

Given that my exercise habits can be best described as erratic and my eating habits have been formed by a lifetime of dieting and falling off the wagon, it felt sensible to draft in some help. Personal trainer, Venetia Cowie, and nutritionist, Eve Kalinik of Wakeman Road, are setting the rules for this week. They include:

• Eat regular meals and include some protein in every meal
• Drink more water
• Avoid any food that could be described as white, fried or dyed
• Get out from behind the desk and go for a walk at lunchtime

Does it work?

For me the biggest test was always going to be eating a regular breakfast. I fall out of bed at the last possible moment each morning and race to the tube, meaning it’s often easy for me to skip breakfast at home and not eat anything until about 11am when I have an energy slump and reach for any form of sugar. On day one I force myself out of bed and throw together a smoothie. Kalinik recommends upping your intake of green, leafy veg as it’s high in chlorophyll. This helps transport oxygen around the body, keeping us more energised. So I throw a handful of spinach into the smoothie, along with some flaxseeds for extra Omega 3s, and feel very virtuous.

“We are around 60% water,” says Kalinik, “so it’s essential to make sure that you are taking in plenty of fluids - diet coke doesn’t count!”

This is actually the part that I find the hardest. I just can’t remember to drink enough water. I try setting reminders on my phone, putting a water bottle on my desk and in my bag so that I’m never without it, but it’s hard. I just don’t realise I’m thirsty. However, one tip that does seem to work is this: drink more in meetings. And no, not vodka. Maybe it’s because in a meeting I’m not permanently locked into my computer but I suddenly start to notice the glass in front of me, and I realise I’m thirsty. Once I have one glass of water, I want another and another.

One thing that makes an instant difference is Cowie’s tip about getting some exercise at lunchtime. Usually this involves moving from my desk to the canteen one floor below, but this week I start trying to actually leave the building and take a walk around the block. I can’t believe how much better I feel for it. I generally have to schedule my day so that all the difficult work is done in the morning because by 2pm my attention span has become non-existent. Just getting outside for a short walk completely changes this.

Cowie also recommends trying to fit in some sort of proper exercise each day. My biggest problem is that after a day at work the only thing I really want to do is collapse in bed, but apparently this is where I’m going wrong.

“After working at a desk all day you may well be mentally drained but your body certainly wont be,” she says. “It may feel it, but don’t mistake lethargy for exhaustion. That lethargic feeling actually means you need to exercise. So suck it up and get it done.”

The results

Can you feel and work better on just one week of healthy living? I’m sort of disappointed to report that the answer is yes. I was hoping that the change wouldn’t be clear enough for me to abandon my usual sloppy ways but it turns out but it turns out there’s a reason all those CEOs are waking up at 5am to run a half marathon every day.

The clear wins were eating breakfast and taking a break from your desk to go for a walk at lunchtime. The first actually forced me to take a bit more time over my morning. I thought losing those extra ten minutes in bed would make me cranky for the rest of the day, but not having to run out of the door actually gave me time to wake up properly and meant I arrived at the office calmer and in better control of my day. Taking a walk midday had the same effect. As well as waking up my metabolism and giving me more energy, it also gave my mind a break allowing it to go into the afternoon recharged.

As suggested by Kalinik, I upped my intake of green veg, Omega 3s and avocados but I suspect it might take longer to really feel the benefit of changing my diet. I can report however, that by the end of the week I had more energy and wasn’t getting the usual 4pm sugar slump. I had been worried that I wouldn’t be able to cut down to just one cup of coffee a day, but I actually felt so much better that I’m now trying to get rid of caffeine altogether.

I don’t know if I’ll ever be a daily exerciser but I did take Cowie’s tip, about not mistaking lethargy for exhaustion, to heart. Forcing myself to exercise through that lethargy actually made me realise how much more energy I had, I just needed to access it. It also meant I slept better and had more energy the following day.

So the old wive’s tale is true: a healthy body does equal a healthy mind and it can make you better at your job. But as Kalinik will tell you, being perfect all the time isn’t healthy either. You need a good 80/20 balance, so the occasional brownie is fine.