august: Do you have your own money for groceries? If you don't have a job and have to rely on eating their food, it will be much more difficult to gain.
Fattlover: Yes i do but they are super overprotective and they will notice it when i buy unhealty stuff.
You can get fat on plenty of healthy stuff. Just eat a lot of it: pasta, potatoes, rice, oatmeal, bread, cheese and other dairy, lots of oil and croutons in salads. When you're out by yourself or with friends go on a junk food rampage.
The list goes on and on. Buying foods like these are also usually cheaper than buying junk food (in terms of calories-per-dollar), though obviously they're good too as caloric supplements. Study up on which foods you like and can fit in your budget and you should be all set. Most online articles about gaining weight healthily will include lists like the one above that suggest good foods for gaining. Here's one, for example:
They're usually written for underweight people, but the principles are the same; just on a larger scale depending on how much/quickly you want to gain.
As for hiding unhealthy stuff from parents (for which I accept no responsibility if it doesn't work ): get an opaque plastic container that's big enough to hold a food stash but that can also be tucked away and inconspicuous when necessary. Worked for me back in the day, anyway.
When I started dating my future wife, her mother would always pull me aside and tell me her daughter was getting way too fat. She was very traditional and old-fashioned and considered it my responsibility as a man to put her on a diet.
Of course she wasn't wrong, it really was my fault she's gotten so huge
But my mother-in-law has eased off recently as my bride continues to grow. I think she understands her daughter is happier than ever- and even healthier too, considering her massive weight gain has really helped with debilitating problems she had as a kid, like anemia and hypothermia.