Usually, the fridge's coils (which are found either underneath or behind the fridge) need a good vacuming with a SOFT 'brush'. What ends up happening is the coils collect dust and, essentially, insulate the coils and prevent them from getting 'cooled' by the surrounding. Hence, an excessive amount of heat is generated which counter-acts a great deal of the cooling effect that the coils are SUPPOSE to produce.
Don't go 'flipping' the fridge over. Slightly tilt it backwards, or frontwards, or backwards, and 'prop' up the 2 corners, and clean the coils (assuming the coils are on the BOTTOM of the fridge.) If the coils are behind the fridge, just pull it away from the wall COMPLETELY (so you can see everything) and vacume.
In addition, assuming everything is 'clean', and the fridge continues to work too hard, it's quite possible that there isn't enough circulating air 'around' the fridge. You would then need to improve ventilation. Again, the heat buildup from the fridge will counteract any cooling effect(s). Soooo, improve the air flow. Perhaps pulling it away from a wall/walls about an inch or 2 will suffice.
OTher than that, maybe the freezer 'return vents' that are INSIDE and towards the rear of the freezer (usually) are being 'blocked' by your frozen foods. And again, improve the airflow INSIDE the fridge/freezer.