change in eating habits

My dog (chihuahua/jack russell cross 4-5kg) is almost 2 years old and she has never been too interested in dog food, there are certain types she prefers over others but even then she did not always eat it. I usually feed her dog food, but occasionally cooked meat or fish. She has always tended to eat the non dog food as soon as I give it to her, however I was reluctant to get into the habit of cooking for her, mainly because with dog food I know all the vitamins etc are included. I mentioned to the vet that she did not often seem to have much of an appetite and he said that this was fine as long as it was consistent and that she had not just gone off her food. I was not particularly concerned about her appetite as just thought that she was not eating the dog food in the hope that I would give up and give her human food instead! After all, we like and dislike certain food so I suppose dogs are the same! Her appetite for fresh meat, fish, treats etc has never been a problem.
Anyway, the reason I am now concerned is that she suddenly seems to be eating a lot. I had started to cut down her portions as so much was going to waste but now we are back to full size portions and she is eating everything usually as soon as I put it down, even the dog food which she has usually turned her nose up at. I still give her things other than dog food occasionally so it can't be that she is eating it as she knows she won't get anything better.
Is it normal for a dog to suddenly have such an increased appetite? She is wormed regularly so it can't be that she has worms - any ideas? It is nice to see her enjoying her food but just want to make sure that there aren't any possible health problems that might cause this. I have thought about taking her to the vet but they may think I am a little bit mad for being concerned that my dog is eating normally!
Thanks and apologies for the long message!

Maybe maturity ? but as long as she isn't being over greedy or anything I'd think maybe she has matured and her system has settled, if your worried phone the vet for advice, don't think they'd think you were mad...x

Having you uped her exercise now with the lighter evenings.
Mine eat alot more now as I take them out on the bike every night now its light. Where when it was dark we didn't go as far.

Hi Nic a sudden increase in appetite can be linked to hyperthyroidism though there are usually other symptoms like loss of weight and the dog becoming a lot more active than normal.

If you are concerned it is best to get it checked out by the vet (a blood test should tell) , it could just be down to your dog getting more exercise now it is warmer weather as Lotsofus has already said , and that has lead to an increased appetite.

Apart from the thyroid problem which has already been mentioned, two other things it may be, one she may have had one or more retained canine teeth that would make eating difficult, not sure about Chihuahua but Yorkies do often retain the teeth and it can cause problems with eating, if this was the case they may now have come out. The other cause may be hormonal, it may be she has a phantom or if she has been spayed in the last 6 months the increase in appetite may be connected to that.

Thanks everyone for your advice and suggestions. She was spayed well over a year ago so can't be anything hormonal, we haven't changed her exercise, she does have a couple of retained teeth but they are still there. And she hasn't lost weight - she has put a little bit on so hopefully not a thyroid problem. Hopefully then it is just that she has decided to start eating normally, I will keep an eye on her for any symptoms but haven't noticed any up to now so fingers crossed there is no sinister reason behind it!
Thanks again for all the advice