Over the last six months the Mitchells & Butlers-owned chain has found that diners have been consuming, on average, 25 calories less since the information was introduced.
Adam Martin, marketing and strategy director for Harvester said it was 'early days' for the move, but that there was definitely a shift in behaviour with diners opting for lower calorie dishes, such as white meat and fish over red meat.
"There are many factors at work here, however it appears that there has been a small, but discernable change in behaviour by our guests," he said.
"Our menu gives customers the flexibility to choose a meal that’s tailored to their taste and calorie preference. Customers have been using this choice by opting for slightly lower calorie side dishes, for example by swapping fries for mash or new potatoes.
“Now, as a number of leading companies like McDonalds follow suit and introduce calories on their menus, it will be interesting to see if other chains see similar results?"
Harvester was the first UK-wide pub brand to introduce calorie labelling onto its menus this year. It is among 45 companies, including The Real Greek and McDonald's who have signed up to the Government's Responsibility Deal.
Alex Meyer, senior marketing manager for Harvester, said: “It was a big decision to become the first UK-wide restaurant brand to print calorie information on menus, but we felt that the time was right for Harvester.
"We were particularly pleased with the response from our customers, showing overwhelming support for the introduction of calories. Following the launch, on Facebook more than two thirds of people were supportive of calorie labelling on our menus.”
Harvester's findings go against those of a similar study carried out by the New York Health Department of chains across the US city. According to the survey of 15,000 customers at 168 fast food outlets, being given calorie information had little impact on their choice.