Previous studies in the area have often focused on adults or school-aged children, or on children in countries with tighter restrictions during the pandemic.

- There are few studies done on preschool children in Sweden, says Anton Holmgren, a pediatrician who does research in pediatrics at the Sahlgrenska Academy at the University of Gothenburg and who is one of the authors of the study.

The study is based on data on roughly 25,000 three- to five-year-olds who have undergone regular health checks at childcare centres, BVC.

- We found, somewhat surprisingly, that even at the lowest ages there was an increase in both obesity, which is the name for obesity in healthcare, and overweight when compared to the previous years, says Anton Holmgren.

BMI increased

The result shows that three-year-olds' body mass index, BMI, increased during the pandemic.

The percentage of boys with obesity increased from 2.4 percent to 2.6.

Among girls, the percentage with obesity increased from 2.8 percent before the pandemic to 3.9 during the pandemic, which means an increase of 39 percent. 

Paulina Nowicka, who is a professor of nutritional science at Uppsala University and a registered dietitian, believes that it may be due to norms in society.

- It can sometimes be more socially accepted for girls of this age to sit inside and do things.

- Girls are expected to be quieter, while boys are not.

At this age, many parents think that the children are spontaneously active, but they are not, she says

The clearest increase was seen in children in socioeconomically disadvantaged areas.

There, the percentage of overweight three- and four-year-olds increased from 9.5 to 12.4 percent, and the percentage with obesity from 2.4 to 4.4 percent.

- It is frightening that already at such young ages there are class differences linked to the risk of overweight and obesity.