The relationship between price and nutritional balance for young adults in the menus of Japanese restaurants.

Background: Eating habits are a contributing factor to obesity. Higher-priced menu items have better nutritional quality/balance, as the relationship between the price of food per serving and nutritional quality/balance has been reported. However, previous studies on the nutritional content of restaurant menu items did not focus on the relationship between the nutritional balance of menu items and prices. Therefore, this study aimed to investigate this relationship.

Methods: The nutritional balance score (NBS) was defined and calculated according to each nutritional criterion of men and women aged 18-29 years, covering more than 2,000 menu items in 26 Japanese restaurant chains. Furthermore, NBS distribution by gender and restaurant brand, and the relationship between the menu item's NBS and price were assessed.

Results: The results showed that the average NBS of the analyzed menu items differed between the criteria for men and women, with the menu items assessed based on men's criterion being more nutritionally balanced on average. The compositions of the top 10 menu items differed between men and women, and most were set menus or rice bowl menus, which were offered by fast-food restaurants. The relationship between price and NBS in most fast-food and casual restaurants was expressed as a concave function. The maximum NBS based on the criteria for men and women were 64.9 and 64.1, with prices of 639.9 and 530.3 yen, respectively.

Discussion: NBS score increased with price to a certain level before decreasing, suggesting that the price at which NBS was the highest differed between men and women. The results of this study could contribute to the development of a methodology for healthy eating out practices, with a focus on price.