The foundation Swiss Health Promotion (GS) has studied the weight of 14,000 students in compulsory schooling in Bern, Basel and Zurich for the past ten years.
According to its latest report published on Monday, 17.3 percent of the students studied during the 2014/15 school year were overweight, and of those a quarter were considered obese.
That's down from a peak of 20.1 percent overweight during the 2010/11 school year and 19.9 percent ten years ago.
The biggest reduction was among children of pre-school age (four percent down on a decade ago), and children from immigrant families (2.6 percent down).
But the report also revealed how obesity rates among school children rise as they get older.
While 12 percent of pre-school children in the last school year were overweight or obese – down from 16 percent ten years ago – that rose to 21 percent for primary school children and 23 percent at secondary schools.
The number of overweight students at secondary school fell for the first time this year after a constant rise over the past three years, said the report.
However, 4.4 percent of school children were considered obese across all schooling levels in 2014/15, a figure that hasn't changed a great deal in the past few years.
In a statement, Lisa Guggenbühl, impact manager for GS, said overall the new figures were “a promising sign”.
“The fact remains that nearly one student in six is still overweight and there are significant differences between school grades and social groups.”
According to figures from Neuchâtel Hospital released in March, 11 percent of the Swiss population is considered obese.