Almost one in six ten and 11-year-olds in Brighton and Hove are classed as obese.
The figures come from children who were weighed during the last academic year.
Health bosses found about 16.4% of children were dangerously overweight compared to 17.7% the year before.
However a recent report to a children and young people's scrutiny committee said the fall was not significant and there was still a lot of work that needed to be done to tackle the issue.
Obesity in children can lead to serious health problems in the future including heart disease, some cancers and diabetes.
It is also linked to self-esteem problems, depression, anxiety and bullying.
Brighton and Hove City Primary Care Trust and Brighton and Hove City Council said they were trying to deal with the problem and said it was a top priority.
Work includes targeting children and families in more deprived areas of the city such as Moulsecoomb and Whitehawk.
Research has shown children in these areas are more likely to have a poorer diet and be less active.
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