More Chinese people aged 20 to 39 are becoming overweight and their athletic ability is declining, according to a national survey released on Monday.

The survey of more than 43,000 adults found that more than 11 percent of people aged 20 to 39 are obese, an increase of 2 percentage points since the last survey in 2010.

The average weight gain of the group was 1.92 kilograms, higher than figures of the other two age groups (40-59 and 60 plus).

The General Administration of Sport survey of 10 provinces, autonomous regions and municipalities also found that 34.4 percent of Chinese between 20 and 69 are overweight.

Tian Ye, director of the China Institute of Sports Science, said the issue of weight and physical decline can be attributed partially to the lack of sports activities among young people.

"We are still analyzing the reasons, but it couldn't be more obvious that the lack of exercise played a negative role," Tian said.

According to the survey, those between 20 and 39 are the least active exercisers. Fifty-one percent of them don't exercise regularly, citing no time due to overloaded schedules.

The results also indicated that waist circumferences and hiplines have increased in all age groups, especially among young males and middle-aged females in urban areas.

Meanwhile, a decline has been seen among young adults in their ability to grip something, jump or maintain balance, indicating losses of strength and flexibility.

"Statistically, the fitness level of this group dropped in line with the decline of their sports involvement. It proved the importance of sports exercise for keeping fit and healthy," Tian said.