World hunger appears to be on the rise again after a prolonged decline, according to the United Nation's (U.N.) Food and Agriculture Organization (FAO) report for 2017.

In the report "The State of Food Security and Nutrition in the World" released in mid-September, the U.N. body said, "The estimated number of undernourished people increased to 815 million in 2016, up from 777 million in 2015."

Experts said global food production should rise 50 percent in order to meet the nutritional requirement, a number estimated to reach 10 billion worldwide by 2050.

The report said 154.8 million children under 5 are still affected by stunting, which equals 1 in 4 children under the age of 5.

"In 2016, wasting affected 7.7 percent [51.7 million] of children under 5 years of age worldwide," it said.

On the other hand, obesity among adults is rising and according to the FAO, "The global prevalence of obesity more than doubled between 1980 and 2014. In 2014, more than 600 million adults were obese, equal to about 13 percent of the world's adult population."

The FAO has declared this year's theme for World Food Day as "changing the future of migration by investing in food security and rural development," the statement said.

It also added that migration has been rising due to famine, poverty and wars since 2000.

"Development policies aiming to provide food security and prosperity in rural areas would decrease the number of motives that make people migrate and improve migrants' living conditions," it said.

The FAO has been celebrating World Food Day on Oct. 16 since 1980. The day is widely recognized by organizations concerned with food security.