Shift workers reach for snacks and eat more later at night which could explain why they face greater health risks than those who work standard hours.

Approximately 1.4 million Australians, roughly one in six workers, are shift workers and most have rosters that change from week to week.

A Monash University-led study found shift workers ate more food late in the day which may explain why they put on more weight and had a greater risk of chronic diseases.

The findings showed on average shift workers ate an extra 263 more kilojoules over a 24 hour period compared to day workers.

That is equivalent to about half a medium sized banana, an apricot or two squares of Cadbury dairy milk chocolate.

Workers who work different shifts week to week were found to eat fewer carbohydrates and protein but consumed more fatty or fried foods.

Increasing energy consumption by just 100 kilojoules per day can add up to about half a kilogram over a year.

Monash University PhD candidate and research dietitian Angela Clark hopes the findings could be used to spark workplace reform and make it easier to buy healthy food outside standard working hours.

"The foods and drinks typically consumed by rotating workers were more fried and fatty foods, confectionary, sweetened drinks and alcohol, with fewer core foods such as dairy, meat, fruit and vegetables," Ms Clark explained.

"Adding to the complexities of night time eating, shift workers don't have the same access to healthy food as day workers and may rely more on vending machines, takeaway and convenience foods."

Scientists from Monash University and the University of South Australia are now trialling three weight loss strategies for shift workers, focusing on circadian rhythms and eating at particular times during the day.