This story begins on New Year’s Eve. I was on the bus on my way to a party, when I began to feel quite sick. A quivering rose from my stomach, and two stops into the journey I began to retch. I leapt off the bus and ran into a coffee shop to get a Danish pastry thick with the kind of icing that coats the back of your throat. I ate it down and just 10 minutes later felt perfectly normal. I had been trying to keep my appetite up for dinner, so had gone without my usual breakfast pudding, mid-morning biscuit and post-lunch chocolate. The sugar withdrawal was sending my head into a migraine and my stomach into a spasm. The episode was a warning: I was dependent on sugar. It couldn't go on. I decided almost on the spot to go without sugar in January – much as many people will do tomorrow, for the start of Cancer Research's Sugar Free February – and instead fill up on foods that would keep my energy up without threatening these desperate crashes. If I felt like I needed a treat after dinner, I would have fruit or cheese. I don’t want this to turn into a debate on linguistics, so I’ll make this clear now: it’s impossible to give up all sugar, which occurs naturally in pretty much everything. I chose to avoid what the NHS calls “free sugars”, things like refined sugar, honey and fruit juice. They are considered less healthy than the sugars in milk or vegetables as they are not bound up with fibre or protein, which slow down your body’s absorption of the sweet stuff and therefore cause less of an insulin spike. On January 1 I went food shopping and filled my trolley with vegetables, beans, fruit, dairy and eggs. Checking the labels of what I could and couldn’t have was eye-opening: almost every packaged food has sugar added to it, regardless of whether it’s sweet or savoury.

I couldn’t bring myself to throw away all the chocolate in the flat, so I put it in a box (it weighed 2.1kg) and hid it on the highest shelf in the cupboard. Out of sight, out of mind – and most crucially, not in my body. After a month of eating and drinking too much, the first couple of days of January actually felt like a relief for my digestive system. I managed any threat of a migraine by making sure I didn’t get too hungry, and by eating fruit whenever I craved a sugar hit. Given my horrible reaction on New Year’s Eve, I expected the first week to be dreadful. But somehow, I was... fine. Completely fine. No headaches, no hunger, no shivering, no sweating. My best guess now is that the addiction was largely in my head. I was eating out of habit and not out of physiological need. After that first week, I started to notice the benefits. My mind seemed clearer at work, and my customary post-lunch slump disappeared. I could now concentrate all day. Well, OK, most of the day.

Free sugars are found in sweets, chocolate, and fruit juices Credit : Martin Barraud

A surprising knock-on effect of this was that my caffeine intake dropped hugely. Usually I would drink three coffees in the morning and another couple after lunch to keep me alert. But since I had no brain fog, I had no need to be chemically stimulated. After a while, the smell of coffee after noon made me feel a little queasy. Around the same time I noticed that my teeth felt miraculously clean: if I pushed my tongue across them with enough force I could actually hear squeaking. It felt like I had had a deep clean at the hygienist every single day. Two weeks in, I saw another bonus: my skin was clearer. The stubborn patches of spots I’ve had on my back for the past few years had disappeared completely. Everything was going so well. I didn’t even really miss the taste; I had plenty of other delicious things to eat, and I felt satisfied. But then my period came crashing in like an aggressive punter barred from a pub. The first day I felt low as anything and realised there was only one thing that could lift my spirits: the magical mixture of coffee and a chocolate croissant. I went to the Pret near the office and bought the goods, then slunk into a corner and drew back the paper of the bag. I gurned wildly, saliva practically gushing from my mouth, and prepared for that first perfect bite. Was that a sunbeam turning its warmth onto my face, or an LED spotlight flickering on?