Hmm. I think it depends on your height, your weight, your frame... and how much you're working out. What IS your height and your weight, and what kind of exercise do you do?
As much as a website can say that your ideal calorie intake should be ______, it can't really know what your body needs based on your lifestyle.
What I would say is: Stick to a calorie intake that seems reasonable. HOWEVER. If your stomach is growling at the end of the day, do NOT walk away from eating because of a number. Simply choose healthily, and grab something like.. a banana, or the tuna thing you're talking about. You should never starve yourself for the sake of what the internet says you should be eating calories-wise.
As for whether 1,200 is an alright number... it's an extreme calorie cut, which is alright if you're not working out a lot, and if you're still getting a good amount of low-calorie food... but getting any less than that starts to become a bad idea. If you eat too few calories in a day, your body switches to "starvation mode"... it thinks you don't have enough food, so it starts storing the fat and garbage from all the food you DO eat, in case the food supply runs out.
I stick to about 1,400 most days, but don't beat myself up when I go over. Today, my calorie intake is planned as 1,200-1,300 because yesterday I ate about 1,600. It's a balancing game for the most part. If you go over today? No biggie. Fix it by being healthy tomorrow. But never ever deprive yourself of food that your body needs to run because of a stringent internet-decided number.
