Every day for the past month complete strangers have bought me lunch. And breakfast. And dinner. And they don’t even know it.

I have been living high on the hog, and it hasn’t cost me a penny – because I have been dining out on the half-eaten fast food and takeaways thoughtfully abandoned by my fellow Britons on pavements and park benches and tube platforms all over the city. Sometimes they even leave them in bins.

I have seen the disgust on the faces of passers-by as I ferret out a few slices of margherita (my favourite, by the way, and so much better garnished with a dusting of cigarette ash) from a pizza box wedged in a bin slot, and proceed to wedge a gooey slice into the slot on my face.

Don’t worry, I also feel a sense of disgust – about the terrible, shocking and casual squandering of nourishment and calories that goes on all around us and seems to be escalating.

Facebook Twitter Pinterest An abandoned takeaway left in a bin at a London tube station. Photograph: Andrew Mayers

The story about the billions of pounds’ worth of food that households throw out rightly receives a lot of coverage. As does the vast tonnage of edibles wasted by supermarket supply chains.

But the street food scandal does not really get talked about. The shame of the millions of unbought meals that restaurants bin is no longer hidden, but there seem to be few statistics about the mountains of nutrition consumers happily toss into the gutter. Which is where I come in as, I believe, the first gutter food critic in the mainstream media. The gutter gourmet, as my friends have dubbed me.

And what I found in the gutter raises serious questions about the cheapness of our food, the obesogenic environments we all live in, and the widespread denial of our sustainability crisis.

Because this is a story that cuts across class, gender and race. I have wolfed down food discarded by black and white people, by football fans and chess players, by the inebriated and the sober, by the LGBTQ community and Tommy Robinson supporters, by Jews and Muslims, by Brexiters and remainers. It’s a very eclectic diet.

Facebook Twitter Pinterest Leftover salad after the lunchtime rush at King’s Cross. Photograph: Andrew Mayers

And the quality – and expense – of the dishes seems to have little bearing on the consumer’s willingness to chuck it away. I’ve savoured the excellent: quinoa salads discarded at the King’s Cross farmers’ market (ooh, I’m getting lemongrass, and fennel, and ... gentrified saliva).

The less appetising: unfinished cartons of chicken and chips tossed away by fellow Gooners on the way to Arsenal games. The frankly dangerous: helping myself to meals abandoned by pub diners, only to discover they have not been abandoned when the diners reappear. And the inexplicable: bags of perfectly good food shopping seemingly fly-tipped on street corners.

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But observation confirmed my expectation of the one thing that united all the diverse food-wasting communities: few of them were old. I was brought up by parents who lived through the privations of wartime and rationing, and they passed on to my generation the credo that wasting food is a sin.

My dear old dad, who died a couple of years ago, watched the world pass by as he worked his south London garden, and I vividly remember his discombobulation – some time in the 80s – when he began to notice people carrying plastic bottles of branded water. This stuff was free and universally available – and yet people chose to buy it. And then throw the bottles away after a couple of gulps. Often into his garden. He thought it was close to madness.

I am very grateful to my parents for the values, the norms of non-entitlement, they passed on to me (apart from the one about only drinking at Christmas). But somewhere we have failed to pass them on, bulldozing them beneath tonnes of landfill. The idea of someone buying a burger, accessorised with 20 napkins and sauce sachets, taking a couple of chomps and stuffing the residue into the nearest hedge would sadden him. But his first reaction would be to find such habituated conduct intensely weird.

Facebook Twitter Pinterest A commuter’s abandoned coffee. Photograph: Andrew Mayers

But it’s not the person who tosses away his half-chewed bun who is condemned as weird, it’s the 57-year-old who goes round picking it out of the hedge and scoffing it. Shifting baseline syndrome, George Monbiot calls it.

I have my standards; like the three-second rule children apply when they drop a sandwich in the playground, I have my own three-hour rule. And if I were to design my own “use by” label for my extreme scavenging brand, it would read: “Best before the third ring of mould.”

But in modern cities I rarely reach these borderlines – there is such an abundance of freshly discarded takeaways, I am scooping them up before they hit the ground. And I am washing them down with so many half-drunk cups of hot Starbucks, I am in danger of a caffeine overdose.

Facebook Twitter Pinterest Overflowing piles of takeaway bags spilling around a bin in Hanover Square, Mayfair. Photograph: Andrew Mayers

By applying these rigorous criteria, I am now in the best shape of my life. In one month of living on what my fellow city dwellers reject, I have not suffered one stomach upset, not one episode of King’s Cross tummy. I feel more streamlined, more connected, less anxious – and my tennis game has improved beyond recognition.

It’s fun being the gutter gourmet. Perhaps word will get around the social media grapevine, and it will become a thing, with groups of bearded hipsters combing the sidewalks of Hoxton, and Instagramming their putrid palate-pleasers.

But for the time being I’m on my own, scrapping for calories with the foxes and the crows. I hope my dad would be proud of me.