The survey commissioned by the BBC found that 55% opt for convenience foods rather than cook dinner themselves on a minimum of three nights per week.
Less than a third (27%) of working-age Scots prepare meals themselves every night.
In more deprived areas, almost one in five (17%) said they did not cook a single evening meal from scratch.
The MORI poll of 1,000 people was conducted for a BBC One Scotland documentary looking at why Scotland is one of the world’s fattest nations.
According to the programme, Scotland is second only to the US in the obesity league table, with two-thirds of adults overweight or obese.
Weight loss surgery increase
The number of people getting weight loss surgery has increased four-fold over the last decade and obesity now costs the NHS in Scotland £200 million a year, it says.
Majid Ali, a consultant surgeon at the University Hospital of Ayr, said demand for bariatric surgery was so great the hospital had to ration it.
He told the programme: “I had an influx of patients, a huge number of patients wanting these operations.
“I had to ration it to the people who would benefit the most which are those who have Type 2 diabetes and sleep apnoea.”
David McAtee, from Cumnock, East Ayrshire, was 28 stone before shedding 15 stone after having a gastric bypass operation last December.
The 43-year-old said: “My mum died from being obese, my step-sister died from being obese. That was really hard. If I hadn’t had the surgery I would have died.”
Mr McAtee, a father-of-one, said supermarket promotions on cheap, unhealthy food do not help people prone to overeating.
The British Retail Consortium (BRC) said it was not true that unhealthy food was being promoted over healthy options.
Andrew Opie, director of food and sustainability at the BRC, said: “It’s actually cheaper to eat good, nutritious food, fresh fruit and vegetables, as it is to buy processed food.”
He added: “There’s nothing wrong with buying those things on promotion as long as you eat them as part of a healthy diet.”
The documentary-makers filmed unhealthy snacks on sale in hospitals and on patient trolleys in the Glasgow area.
Public health minister Michael Matheson said health boards should ensure the healthy eating messages were being followed.
He told the programme: “If there is an issue where some of our boards are giving out mixed messages around healthy eating and are not giving sufficient prominence to issues around healthy eating then I think they should look at taking action.”
Scotland the Fat is screened on BBC One Scotland at 8pm tonight.