Reducing food waste is necessary for achieving healthy diets and sustainable food systems due to its negative impacts on resource conservation, food security, and environmental, social and economic costs. This paper aim is to quantify the amount and types of food that is wasted by the consumers in different restaurant configurations. The second aim is to understand the reasons which lead them to waste food and the greenhouse gas emissions associated with the waste. To fulfil the aims, a mixed methodology was used, including primary data collection in restaurants for the quantification of food waste, interviewing consumers and staff, along with calculating the environmental impact from the waste using life cycle assessment. The results show that different incentives and levels of interaction in consumer’s choice of food types exert influence on plate food waste. When incentive and interaction are low, the amount of food waste is larger. It is the case of a la carte restaurants. The best performance in the restaurant categories was when both incentive and level of interaction were higher. Buffet where the consumers pay by weight, therefore, is the configuration that generates less food waste on the consumer's plate. The main wasted products are rice and beans, followed by beef, and then other carbohydrates. The life cycle assessment indicated a carbon footprint varying from 128 to 324 g CO2 eq./plate from the wasted food. The result of the interviews showed that the food waste on the plate is not visible to consumers, since in the majority of cases, they believe that their food waste on the plate in the day of the observation was an exception. There is a large potential to reduce food waste by giving consumers the possibility to influence the serving to get the right portion size. Also, to further emphasize this behaviour by creating incentives for consumers only to serve as much food as they actually eat.