"In theory but the benefit would be pretty negligible i think. Let's say for argument that most food is water and your fridge is 25% food and 75% air. The specific heat of air is 1 kJ/kgK, specific heat of water is 4.2 kJ/kgK. But also the density of air is 1.2kg/m3 and the density of water 1000kg/m3. Assume 1 m3 volume. So that would be 250kg food and 0.9 kg air. To change temp by 1C would take .9kJ for the air and 1050kJ for the food. So the air in a fridge holds a fraction of a percent of the total thermal mass of the contents. Whether or not that air changes temperature by a few degrees won't change things much at all. You would spend far more on balloons that you would save on energy."

* https://www.reddit.com/r/AskEngineers/comments/1618mku/would...