Parents often underestimate how fat their children are - but so do family doctors.
Mothers and fathers also prefer to use terms such as "big boned", "thick" or "solid" rather than describing their child as obese or overweight.
The new study found that more than half of parents (54 per cent) underestimated whether their child was overweight or obese.
Meanwhile, 34 per cent of children and adolescents also underestimated whether they were fat, while doctors also tend to think children are lighter than they were.
According to the study, parents of younger children were less likely to think their child was overweight, and were less accurate at judging the weight of boys than girls.
Researchers also found that less educated parents, and those who were overweight themselves, tended to not regard their child as overweight.
The experts, presenting their findings at the European Congress on Obesity (ECO) in Glasgow, examined existing data from 87 worldwide studies carried out between 2000 and 2018.
These included 24,774 children aged 19 and under, and their parents.
Abrar Alshahrani, from the University of Nottingham, who led the study, said: "Despite attempts to raise public awareness of the obesity problem, our findings indicate that underestimation of child higher weight status is very common.
"This misperception is important because the first step for a health professional in supporting families is a mutual recognition of higher weight status.
"This is particularly important for the child themselves, the parents, and the health professionals who look after them.
"Our study also found a tendency for health professionals to underestimate weight, which suggests that overweight children may not be offered the support they need to ensure good health."
Professor Helen Stokes-Lampard, chairwoman of the Royal College of GPs, said: "Nobody wants to think of themselves or their child as overweight or unhealthy, but the stark truth is that overweight and obese children face numerous, serious health-related problems - both physical and mental - in the years ahead, if their weight is not addressed".
Australian Associated Press