To understand price incentives to upsize combination meals at fast-food restaurants by comparing the calories (i.e. kilocalories; 1 kcal = 4·184 kJ) per dollar of default combination meals (as advertised on the menu) with a higher-calorie version (created using realistic consumer additions and portion-size changes).

Combination meals (lunch/dinner: n 258, breakfast: n 68, children’s: n 34) and their prices were identified from online menus; corresponding nutrition information for each menu item was obtained from a restaurant nutrition database (MenuStat). Linear models were used to examine the difference in total calories per dollar between default and higher-calorie combination meals, overall and by restaurant.

Ten large fast-food chain restaurants located in the fifteen most populous US cities in 2017–2018.

None.

There were significantly more calories per dollar in higher-calorie v. default combination meals for lunch/dinner (default: 577 kJ (138 kcal)/dollar, higher-calorie: 707 kJ (169 kcal)/dollar, difference: 130 kJ (31 kcal)/dollar, P < 0·001) and breakfast (default: 536 kJ (128 kcal)/dollar, higher-calorie: 607 kJ (145 kcal)/dollar, difference: 71 kJ (17 kcal)/dollar, P = 0·009). Results for children’s meals were in the same direction but were not statistically significant (default: 536 kJ (128 kcal)/dollar, higher-calorie: 741 kJ (177 kcal)/dollar, difference: 205 kJ (49 kcal)/dollar, P = 0·053). Across restaurants, the percentage change in calories per dollar for higher-calorie v. default combination meals ranged from 0·1 % (Dunkin’ Donuts) to 55·0 % (Subway).

Higher-calorie combination meals in fast-food restaurants offer significantly more calories per dollar compared with default combination meals, suggesting there is a strong financial incentive for consumers to ‘upsize’ their orders. Future research should test price incentives for lower-calorie options to promote healthier restaurant choices.