Many obese and overweight pupils are discouraged from taking exercise by their experiences during PE lessons, according to research.
It also found that PE reinforces a sense of inadequacy and abnormality in overweight pupils, even when classes are designed to encourage healthy living.
Suzanne Groves of Chichester University, author of Physical Education and Obesity Issues, claims obese pupils often feel they do not have the right to participate in PE lessons, even when they enjoy physical activity.
Young children, she said, derive a sense of their ability from their teacher. If the teacher does not motivate or encourage them, they are unlikely to engage in PE: "The demands being placed on the profession are sufficiently diverse as to result in teachers being unable to address the specific needs of these children within PE lessons."
Peer responses and bullying during PE also have an impact, she said. Schools, Dr Groves concluded, should provide classes which cater specifically to the needs of overweight pupils, reducing self-consciousness.