Is 'zero' the hero? Living off the latest food craze for a day.

Korea is in the grip of a "zero" craze. Coke Zero has long been a staple, but now there's also "zero" bibimmyeon (spicy cold noodles), "zero" chocolate-flavored cookies and even zero-calorie hangover cures.

The "zero" banner usually means "zero calorie," "zero sugar" or both. The trend has reached an inevitable crescendo with 24-hour stores built entirely around the "zero" label — not zero-sugar products alone but the whole low-calorie, low-carb, diet-food family gathered under the banner — sprouting up across Seoul.

Then came the curiosity about whether I could survive an entire day living off just zero products and if that would make me healthier in any way.

The number of zero-sugar products officially in production hit 590 last year, more than double the year before, according to the Ministry of Food and Drug Safety.

For this challenge, I set myself some rules: three meals or fewer, all from a zero store; water and black Americanos permitted; and no cheating. My base was Halo Zero, a small chain with five branches around Seoul. The one I visited, in the Hapjeong neighborhood of Mapo District, western Seoul, opened in January and is unstaffed — no employees, just shelves, a fridge and self-checkout.

The range inside was startling: Alongside the diet drinks sat full meals, snacks, desserts, even gum, and I kept thinking, "Even this is supposed to be low-sugar?"

What ‘zero’ even means

Here is where the first surprise surfaced. I grabbed a drink off the shelf, read “zero sugar” on the front and turned it over — the calorie count was printed plainly on the back, in the double digits.

Not a contradiction, just two different claims, it turns out: In most cases, the sugar has simply been swapped for a sweetener, usually erythritol or allulose. “Zero sugar” and “zero calorie” are not the same thing, though shoppers routinely read the first and assume the second.

That confusion apparently grew common enough that regulators stepped in. As of Jan. 1, the Ministry of Food and Drug Safety requires any product claiming to be “zero sugar” or “sugar-free” to spell out which sweeteners it uses and how many calories it actually contains.

There is a deeper irony, too: Take out the sugar and what's left is still a heavily processed product — sweeteners, emulsifiers, preservatives, often a sodium count no one put on the front of the box. “Zero sugar” polices one ingredient and waves the rest through.

My assumption walking into the zero convenience store was straightforward: It would all taste bland, and I wouldn’t last a full day — two or three joyless diet meals and I’d be reaching for something real by midafternoon. I was half right.

Lunch, at a museum

I don’t eat breakfast, so the day started with shopping. Around 8 a.m. I hit the Halo Zero Hapjeong branch for a brown-rice konjac marinated rib gimbap (seaweed rice roll), a pack of bite-sized spicy seasoned chicken breast, and a cup of janchiguksu (feast noodles) — a haul meant to last two meals, lunch and dinner.

The low-calorie math was worth understanding. The gimbap swaps most of its white rice for konjac and brown rice — konjac being a near-calorie-free, spongy root that fills you up without the carbs; the entire roll of gimbap thus being only 330 calories. The chicken breast came precooked, at 155 calories. And the noodles promised gluten-free rice flour and around 160 calories — suspiciously light for a bowl of noodles that would normally run closer to 300. 

Even if I decided to eat everything for one meal, the calorie total would clock in lower than an ordinary lunch. Imagine dividing that into two meals. I was confident I would feel healthier and lighter at the end of the day. 

I ate at an unusual venue. I had a press conference to cover at a museum in Gwacheon, Gyeonggi, so lunch — the noodles, plus half the gimbap — happened there at 12:20 p.m., in a quiet corner where one hopes not to be noticed unwrapping convenience store food.

The gimbap was the surprise of the day. I don’t normally like konjac — its rubbery, faintly nothing texture has always put me off — and I opened the packet bracing for disappointment. Instead, it was properly good, a genuine variety of flavors coming together in a way that made me forget what was standing in for the rice. The sweet and savory flavor of the marinated rib sauce took away the usual pungent smell of konjac.  Unlabeled, I’m not sure I’d have clocked it as diet food at all.

The janchiguksu was the opposite. The gluten-free noodles looked and tasted like plastic — slippery, weirdly resistant, unwilling to mingle with the anchovy broth they sat in. Feast noodles are meant to be humble comfort food; this was a clear broth with something adjacent to noodles suspended in it. The missing calories were showing.

The 4 p.m. wall

Here is the part I’m least proud of. I finished the second half of the gimbap as a snack, chased it with an iced Americano at 2:40 p.m., and felt briefly fine — coffee’s borrowed sense that you’ve eaten when you haven’t. It bought me an hour.

Then, around 4 p.m., the hunger arrived — not with a polite growl but a full, insistent, all-consuming roar that reorganized my priorities. I don’t normally get so hungry at that hour, and the only thing to blame was the all-zero lunch, which had been, by my body’s account, barely a lunch at all — at roughly 160 calories for the noodles, more or less true. This is the trouble with subtracting calories from food: Your stomach doesn't know the food's been reformulated. You're just left hungry sooner.

My hand found my phone — less a decision than a reflex. I opened the delivery app and started, on autopilot, to browse fried chicken and jjajangmyeon (black bean noodles) and every warm, dense, calorically honest thing the app arranges by proximity and speed. I got as far as picturing the order.

I didn’t order — and I want that on the record, because for a minute it was a genuinely open question. I closed the app, drank a large glass of water and sat with the discomfort until it passed. And it did pass. That was the lesson of the day: The hunger peaked at 4 p.m. and never climbed that high again. If the premise was ever going to beat me, it was right there, with a fried-chicken thumbnail glowing on my phone, but it didn't.

Dinner, and a second trip

Dinner at 6:30 p.m. was the precooked chicken breast I’d carried since the morning and a great deal of water. The flavor was anything but functional.

By 9 p.m. I was hungry again, my stomach clock all out of whack, and back at Halo Zero for a pack of chicken-breast kimchi mandu (dumplings).

My total across the four products came to 18,470 won ($12.50) and just 890 calories in total, 58.1 grams of protein and just 17.2 grams of sugar, mostly in the form of stevia sweetener— a full day’s food that wasn’t quite a full day’s food. By the time I finished the mandu, the honest inventory was this: a little gassy — the sugar alcohols will do that — and not really full. Not hungry, exactly, but not satisfied either, suspended in a low-grade wanting that no amount of water resolved.

And there was the deflating joke of it: I’d spent a whole day eating “for my health,” and the most tangible thing my body had to show for it was a stomachache from the sweeteners. Nothing I’d eaten was food the way an apple or a bowl of rice is. It was engineering — sugar removed, a dozen other things added — and my gut knew the difference even when my head was willing to call it a diet.

Would I recommend living on zero products for a day? Not really — but I wouldn’t write off zero stores either. As a way to supplement your eating, the category is genuinely good: Swapping one meal, or half of one, for a zero product — the konjac gimbap especially — is a painless trade. As a total diet, though, it left me underfed and faintly deflated. These products are built to sit alongside real meals, not to replace them. After a full day of eating only zero, I lost half a kilogram in just that one day.

Will I go back to Halo Zero? Yes — but for snacks, not another full day. Nobody built a zero-calorie convenience store expecting anyone to live in it. They built it for the person who wants a less fatty snack and then goes home for dinner.