STRESS eating and drinking, more alcohol and less exercise has contributed to people gaining weight around the globe during the pandemic, a Newcastle academic says.
Laureate Professor Clare Collins said roughly a quarter of people surveyed had gone up a belt notch or a dress size during the COVID-19 pandemic.
But if there was a silver lining to come out of the global lockdowns, it was the extra time people were spending cooking their own food, particularly vegetables.
Laureate Professor Collins hopes people can "build on those positives" and focus on improving diet quality for longer term health.
"At this time of year, people can fall into the trap of a fad diet in an attempt to lose weight ASAP," she said.
"Before you do, consider that it may be better to focus on your nutrition and eating patterns, rather than looking to the latest fad diet.
"Fad diets are like taking a chunk out of your bank account for a quick fix. Whereas if you take the time to develop healthy eating patterns, it's like superannuation - it perhaps doesn't pay off straight away, but it does over time, which is what several studies are showing us."
Laureate Professor Collins said a US study of 210,000 adults followed for up to 32 years found that irrespective of body weight, having a high diet quality was associated with lower risk of heart disease and stroke.
A "high-quality" diet included a lot of variety within the basic food groups of vegetables, fruit and wholegrains, with limited junk food.
Similarly, a Swedish study followed 79,000 adults over 21 years and found that among people with a higher body weight, having a high-quality diet was protective against dying from any cause.
But having a body weight in the healthy range was not protective among those who had a low-quality diet.
Laureate Professor Collins said the University of Newcastle's free open online course, beginning this week, would give people the tools to tackle COVID-related weight gain while dispelling common diet myths.
She recommended people continue to plan and cook more of their meals at home, and to eat more fruits and vegetables.
She said it was also helpful to keep a food diary for a couple of days to monitor nutrient and calorie intake to help create more awareness of one's eating habits, particularly snacking.
"Weight gained during COVID varied from countries like Hong Kong and Germany, where about 25 per cent of the people surveyed said they'd gained weight," she said.
"In Australia, Canada and the UK it was about 45 per cent, but in countries like Brazil and Italy, it was over 60 per cent.
"In the US, about 50 per cent said they had gained less than three kilos, about a quarter said three-to-four kilos, and about a quarter said it was more than 4.5 kilos.
"Three-to-four kilos is like a clothing size - so about a quarter of people have gone up a belt size or a dress size during COVID.
"But rather than beating ourselves up about a little bit of coronavirus weight gain - focus on nutrition, and keep the good bits we've learned from the pandemic."
The University of Newcastle course would give people "all the information" they needed to work out the best approach for managing weight gain, but it was a "course for everyone".
It covered portion sizes, how to calculate energy requirements, and how to maintain healthy behaviours.
Enrol for the course via edx.org/course/the-science-of-weight-loss-dispelling-diet-myths. The university is also looking for participants to answer a questionnaire before and after the six-week course via UONnutrition@newcastle.edu.au.