"You absolutely do not need to be vegan [for health benefits]. I would say be a flexitarian," said Clare Collins, Professor of Nutrition and Dietetics.

A flexitarian diet includes a focus on plant-based meals while sometimes consuming food like red meat, poultry and seafood.

Professor Collins questioned why the word vegetarian seemed to have gone out of fashion.

A "plant-based diet" is becoming increasingly common, but Professor Collins is suspicious of the term.

She's concerned that a boom in "plant-based food" will emerge in supermarket aisles.

"We're already seeing a massive explosion of ultra-processed foods that say plant-based on the label. I think it's buyer beware," she said.

"You want to be an old fashioned vegetarian that's eating more plant-based food because you're eating more fruit and vegetables and a bigger variety, and you're diving into legumes, nuts and seeds.

"You don't want to have a shopping trolley full of packets of frozen, just-add-water products that say, 'hey I'm plant-based'."

She liked that the plant-based eating idea meant "we're talking about healthy eating and it allows us to talk about vegetarian food".

"But for many people being flexitarian is more realistic," she said.

She said research in 2010 showed that only half of those who considered themselves vegetarian stuck to that way of eating.

"I think this is what will happen with veganism. People will say, 'yeah I'm a vegan, except for when I'm having my burger'," she said.

"Everybody can be a flexitarian. It's not about giving up meat, it's about focusing on the best quality sources of animal protein [like lean beef, chicken and fish] that you can afford with those rich sources of nutrients."

She said being flexitarian could involve not eating meat for three or more days a week, instead choosing protein sources such as lentils, chickpeas, soya beans or red kidney beans.

On days when meat is eaten, these protein sources could be combined with less meat than usual to further reduce meat intake.

Professor Collins said going vegan could risk deficiencies in nutrients such as vitamin B12, iron, calcium and iodine. Long-term vegans should also monitor levels of vitamin D, omega-3 and protein.

But vegans assert that these challenges can be met without resorting to animal protein.

The vegan trend has risen with widening concerns about animal agriculture, factory farming, animal welfare, climate change and the environment.

Documentaries on Netflix such as The Game Changers and Cowspiracy have echoed rising awareness about animal agriculture and increased vegan activism.

The Game Changers, released in September, made the case that people could live healthily on a vegan diet, even high-performance athletes. It also highlights the serious impact that animal agriculture is having on the planet.

Research shows that using animals for food requires massive amounts of land, food, energy, and water.

Voiceless, an Australian organisation, says factory farming produces the "highest quantity of meat, eggs and dairy at the lowest possible cost".

"Every year, hundreds of millions of animals in Australia are confined in factory farms," it asserts.

"Kept in a state of permanent confinement, animals are often crowded together in cages or sheds.

"Producers use a variety of artificial methods to increase production, such as the constant administration of antibiotics and artificial lighting."

It added that research had shown that farmed animals are "sentient, emotionally complex, intelligent and have rich experiences of the world".

The United Nations Food and Agriculture Organisation estimates that livestock production is responsible for 18 per cent of greenhouse gas emissions.

The UN released a report last August that said switching to a plant-based diet could help fight climate change. Including more "coarse grains, legumes, fruits and vegetables" in people's diets could help the world limit and adapt to climate change, it said.

The UN report found it would be beneficial for the climate and human health if people in rich countries consumed less meat.

Meanwhile, alarm has been rising globally about deforestation in the Amazon rainforest for cattle farming.

These issues have coincided with mounting concerns about food marketing, processed food and "fake healthy foods", amid the obesity epidemic and increasing levels of disease caused by poor diets.

Professor Collins said eating vegetables and fruits could "definitely treat and prevent certain diseases".

She added that the Australian dietary guidelines advise people to eat more vegetables and fruit.

"They're designed to prevent a lot of the chronic diseases that we have," she said.

She said the healthiest foods - vegetables and fruit - "don't have a marketing budget".

"If I had my way, I'd put a tollgate at the end of the vegetable and fruit aisle and stick a food policeman there and say, 'No you haven't got enough, go back and have another go'."

As for concerns about food production, she said the world's food system was geared towards "optimising farming methods".

"In some countries, the greatest equity is around small but efficient farms. In other countries it's around having bigger efficient farms and efficient transport."

She said reducing food waste was another problem that needed discussion.

"That's why I'm not against all food packaging. For some foods, you're better to have it packaged because it keeps better," she said.

A large amount of food was wasted at the farm gate because of fussy people who "only want apples [for example] that have the perfect round shape".

She urged people to check out a website developed by the University of Newcastle called No Money, No Time.

The website features cheap recipes and diet facts.