That’s the conclusion of a new Australian study that found kids were likely to gain weight and lose fitness during school holiday periods.

The findings and their implications for kids’ “fatness and fitness” are significant for a number of reasons - not least that Australian children spend a full quarter of the year on holidays.

The research, published in the journal BMC Public Health, found children’s use of time was significantly different while on holiday compared to term-time. That part was not surprising!

Australian children spend a full quarter of the year on holidays.

On average, the nationally representative sample of kids studied slept 40 minutes longer than during term time and racked up an hour extra screen-time, watching more TV and playing more online games. They also spent 10 minutes less time in “vigorous” physical activity.*

Time spent sitting actually decreased during the holiday period by an average of about half an hour a day. (Kids do sit a lot at school.) But their total energy expenditure was lower by some 5.5%. 

And that, the researchers point out, could eventually add up to substantial weight gain and lowered fitness. 

The activity patterns they found predicted the average child would accumulate 650 g of body fat over the six weeks of summer holidays.

What’s more, the differences between holiday and term-time activity were constants, regardless of parents’ education level, socio-economic status or weight status.

Researchers point to a “counterintuitive asymmetry in the effects of reducing and increasing healthy behaviours.” Translation: it’s much harder to regain fitness than it is to lose it. 

The activity patterns they found predicted the average child would accumulate 650 g of body fat over the six weeks of summer holidays. On that basis, the researchers have stressed the need for “interventions promoting healthful activity patterns during school holidays.”

* Note: this study, "Life on holidays: differences in activity composition between school and holiday periods in Australian children," although published in 2019, was based on 10-year-old data. Its authors point out that screen-time averages are likely to have increased substantially since then.