Companies are stepping up efforts to curb food waste in Japan where 6 million tons of edible products are discarded annually, with major convenience store operators the latest to introduce measures to address the issue.

But restaurants and households that are responsible for some 66 percent of discarded food are moving more slowly to slash leftover items, with eateries concerned about losing customers if they serve smaller portions and Japanese consumers prioritizing product freshness.

Convenience store operators Seven-Eleven Japan Co. and Lawson Inc. said Friday they will start discounting rice balls and lunch boxes as they near the end of their shelf life.

Under the scheme, they will offer customers enrolled in the chains' point programs shopping credits worth 5 percent of the value of the purchase when buying such items.

"Food loss is a big problem domestically and globally as well, so convenience stores also need to confront this issue," Lawson President Sadanobu Takemasu told a press conference. "We will continue to make efforts to sell out our food products."

Takemasu said that around 10 percent of the chain's rice balls and lunch boxes are currently being discarded as waste.

According to the U.N. Food and Agriculture Organization, roughly 1.3 billion tons of food is wasted globally every year, while one in nine people in the world or 815 million are undernourished. Overproduction of food and incineration of food waste consumes energy and contributes to carbon dioxide emissions.

In its sustainable development goals, the United Nations calls for halving per capita global food waste at the retail and consumer levels and reducing food losses along production and supply chains by 2030.

Against this backdrop, agriculture ministers from the Group of 20 major economies meeting earlier this month in the Japanese city of Niigata agreed to take a leading role in reducing food waste.

"Productivity needs to increase and distribution needs to be more efficient, including by reducing food loss and waste, in order to achieve food security and improve nutrition for the growing world population," said the ministers' declaration issued after the two-day meeting on May 12.

The Japanese government has also been pushing to reduce food waste amid rising global awareness of the issue, which is linked to greenhouse warming and poverty.

In January, Japan's ministry of agriculture and fisheries in January urged industry groups of convenience stores and supermarkets not to overproduce seasonal sushi rolls.

The request by the ministry, the first of its kind, came after images of large amounts of discarded sushi rolls went viral on social media, sparking controversy.

"Reducing food loss means less waste of natural resources and it is also important from the standpoint of easing burdens on companies and households," Chief Cabinet Secretary Yoshihide Suga, Japan's top government spokesman, told a press conference on Friday.

"Related ministries and agencies will continue to work as one" to deal with the challenge, he said.

While convenience stores and supermarkets tend to be blamed as massive waste producers, the retail sector discarded only around 10 percent or 660,000 tons of the total 6.43 million tons in fiscal 2016 through March 2017, according to government data.

Food-related manufacturing and restaurants sectors, meanwhile, threw away 1.37 million tons and 1.33 million tons, respectively. Households alone made up over 40 percent of the total at 2.91 million tons.

Among companies that have been taking steps to address the issue of food waste are major restaurant chain operator Skylark Holdings Co., which offers customers a container in which to take home leftover food, although the concept of a doggy bag has yet to take root in Japan.

Other initiatives include that begun by Prince Hotels Inc., which has introduced plates with nine partitions at a buffet-style restaurant it operates in the resort town of Karuizawa, Nagano Prefecture, as a way to discourage diners from helping themselves to more than they can eat.

Some local authorities, including the Saitama prefectural government, have even taken to urging people who organize parties to encourage revelers to finish all the food they order.

Restaurant operators remain wary that serving smaller portions could prove a turn-off for their customers. "It's up to the customer whether or not he finishes his meal," a restaurant official said.

As for household food waste, which the government has targeted slashing by 50 percent by fiscal 2030 from levels in fiscal 2000, amounts have been edging up of late. This likely reflects Japanese food culture's emphasis on product freshness and safety, and shows that where tackling food waste is concerned, the country still has much to do.