Small-portion pre-cut and packed watermelon items of various sizes are on a display at a supermarket in Seoul, June 10. Yonhap

Park Ki-mook, an office worker in his 40s who lives alone, explains that the ability to purchase increasingly smaller portions of watermelons over the years is why he opts to shop at discount store chains whenever he craves fresh summer fruit.

"I had to buy a whole watermelon when I started living by myself in the mid-2000s, but as time went by, stores have cut them it into halves, then quarters and even into eight equal slices to sell," Park said.

"I regard such a sales strategy as perfectly customized for one-person households because we can choose the right size for a dessert, instead of buying a whole watermelon and then having to watch most of it rot in the fridge," he added.

Park represents a rapidly growing segment of single-person households in Korea, contributing to increased demand for groceries and food sold in smaller portions in recent years.

According to Statistics Korea, the country has seen a continued rise in the number of one-person households since 2015 when it accounted for 27.2 percent of total families.

The rate surpassed 30 percent for the first time in 2019, rose to 31.7 percent in 2020, and reached a record high of 34.5 percent in 2023.

Such an increase comes amid changing demographics, with fewer people getting married and more people living longer, according to the statistics agency.

"The trend is likely to accelerate," it noted, pointing out that people in their 20s accounted for the largest share of 19.2 percent among all one-person households in 2023, followed by those in their 70s at 18.6 percent and those in their 30s at 17.3 percent.

Under the circumstances, retail companies are downsizing portions of a range of groceries and food items they sell, including meat, rice, fruit and vegetables, and even pizza.

Lotte Mart, a discount store chain, said sales of its sliced apple packs, each weighing 150 grams, grew 70 percent in 2023 from a year earlier when it introduced the product.

It also said sales of watermelons sold in smaller portions, by the slice or as a chunk, from May 1 to June 11 shot up five-fold from the previous year.

The downsizing of groceries and food items is also noticeable at convenience stores, which are frequented most often by people from one- or two-person households.

The country's No. 1 convenience store brand, GS25, said it saw a 22.1 percent year-on-year sales increase in the January-June period for its fruit salad cup.

Also, sales of Korean side dishes sold in small packages expanded 28.9 percent year-on-year in the first half this year, the company said.