A transportable device for heating food is provided. The device includes a container for receiving the food, a heating compartment, which is thermally coupled to the container by way of a heat-conducting wall, calcium oxide being present in the heating compartment, and a liquid supply unit including a liquid reservoir chamber, in which a water-containing liquid is present, wherein the liquid supply unit is designed so that, based on actuation on the part of a user, the water-containing liquid is brought into contact with the calcium oxide, or the substance mixture including calcium oxide. The water-containing liquid has an elevated dynamic viscosity, in comparison with water, of between 2 and 30000 mPas, and preferably between 50 and 1000 mPas or, alternatively, the liquid supply unit comprises a water retention agent. In both alternatives, the reaction between calcium oxide and water is damped and delayed.