I've a pair of close friends with overweight children. The older boy now has breasts that ressemble my 32Bs. They've been known to complain about the letters sent home from school. It's a fair point that the children have a broad bone structure, but over time it is increasingly being covered in surplus fat. They think my children are skinny and underwight. They are naturally lean, and ribby, with visible muscles. They are on the bottom end of healthy, as were DH and I as children. DS1 has been regularly monitored by dieticians and through other health professionals and has always come out as being healthy. But it's my children that look thin and anomalous compared to their peers.
There should be regular montoring. YR to y6 is too long and the damage is done. Too many cute, chubby 4-5 year olds that still look toddlerish at that stage are easily dismissed, and by the time they are in juniors they are plainly carrying surplus fat. For many that will accelerate puberty.
Poverty is not the only cause. Constant access to sweets, snacks etc and excessive portions size affects all incomes.
My DCs don't seem to have changed through lockdown, we've tried to restrict screen time, and get out regularly to exercise. I have failed to recognise classmates on zoom calls though.
Our organised activities are still heavily restricted. Swimming pools are still not accessible to families. No junior parkrun (free). No indoor martial arts.
Parents need to be objective about their children's health. We need to be pointing out what a healthy bodyshape is like. Children know it anyway, they are often less stupid and deluded than adults!
There also nreds to be accessible, inclusive support.
People fear children developing eating disorders but don't seem to register that obesity often is the outcome of disordered habits, and they are allowing or encouraging what they fear anyway.