I am fine-tuning the inception-v3 network(pretrained on ILSVRC) of tensorflow in a binary classification problem. I want to recognize if an image contains food or not. My dataset is imbalanced, the non-food class contains 5 times more images than the food class. I read that in an imbalanced dataset, I should train the network with balanced batches to get right results. So I split the dominant class in 5 splits and when I have to train the network for 50000 iterations I am changing the split every 10000 iterations, so that the batches that are passed to the training are balanced with food and non-food. I am testing the network in a balanced test-set. From the first 5000 iterations I am getting high accuracy in the food images, but the non-food class gives me imbalanced accuracy. I can receive high accuracy in the beginning and then it will be low. By accuracy I mean (number of rightly predicted food) / (number of food) for the food class and respectively for the non-food. Generally the network learns the food characteristics because the softmax can output non-food for a food image, but the localization of food would be right using the weights of food (I made test). To sum up, the network is probably overfitted but I don't know yet. Any ideas of what might be happening?
Big number of false positives in binary classification
machine learning;neural networks;computer vision