Lifestyle tips

If you are worried about what others will say it sounds like you have a fantasy about gaining.
If wanting to be fat were a reality you would find a way to do it no matter what or what others thought.
Recognizing reality and fantasy are two different things is a start.
I started gaining to get back at a an abusive husband.
one time and the second time I wanted so bad to get fat that I did it and what others thought didn't matter.
Sure friends said things about my weight and my Mother still complains I am too fat.

Why are the opinions of others so important to you is my question for you.
I was really skinny and hated being that way that was my reason.
I was tired of felling bad all the time was another reason.
Its not like you are going to get obese in a matter of months its going to take years to get there.
You are 18 now and in 3 to 4 years a lot of your current friends will be gone doing their thing and you will have a whole new set of friends so they will only know you as chubby

John the OP is 18 and has no experience in the matter and maybe confused as to exactly what he wants. Maybe lighten up a little and help the kid to understand what he really wants or doesn't want.
He was asking questions and thats always where learning starts.

People always will say things and not in positive way, you have to be prepared for that, if you willing to become fat. I was very skinny and started to gained weight only recently, after years of efforts. Like what Ditzy said, it takes years of eating to really transform your body, from a skinny one to really fat. Most of my friends did not say anything about my new weight (Women at work just feels more comfortable to offer me snacks 😸). It's family that usually comments on the issue, in my case. So, eat up, take a decision (whatever it's to gain weight or not, it up to you), and after that do whatever you can to become fat, real friends will not leave you because of that, and you always will have a new ones. Don't let people stop you from doing things. It's your life, not theirs.

MottiF makes some great points.
You are living for you not someone else.
Parents will always stick their nose in anything you do until you are out on your own so if you live under their roof its their rules for now but that doesn't mean what you eat when you are not at home.

I was in a similar situation for years. Like most people here the idea of gaining was something I really wanted. But, I just couldn't go thru with it. Even the one time I kinda did, I shortly after lost it all. First, it seems you have many years ahead of you. I am now just into my 40s and have finally am really going thru with gaining. Family have commented. But, not only was I normally underweight, but I have been on medications that cause weight gain. At this point in my life, I do not care what others think of me. I am happily married and old, lol. But, I do say to my family that my weight change is from medication, just so I don't have to hear it over and over again. As many have said, if you can't get past that point, keep it a fantasy for now. Later on when you are older and have settled down a bit, then give it a try. Best of luck!

Oh, and to add another thing about people who worry "what others think". The vast majority of people are thinking just like you. "What will others think" meaning they aren't thinking of you or your weight gain or whatever. They are thinking about themselves. We are all basically self-centered. Which of course makes sense, because it's our brains thinking. We get all hung up on what others will think, when in reality they aren't thinking about others, they are thinking about themselves too.

Think of of it this way you don't tell others what to do in their life so why should they feel they can tell you ?
At 18 peer pressure is a huge thing and every thing revolves around friends but as you mature you start to think more for yourself and their opinions don't matter so much.

Thanks Skinny boy.
I just comment on what I know and have experienced thru out my own life, other people may have experienced it differently so their points are valid too.

everyone has made really great points so far (well, with the exception of the poster directly above ).

we were having a discussion last night at dinner around how people get to the point that they do what they want, or follow the path they want to, rather than do what pleases others or others expect them to... it's a complicated, difficult subject.

i think my advice would be, don't feel badly if you haven't figured it out now. or this summer. or this year - there's lots of time. you might find in your mid-20s you feel differently. it's not a race. i think the worst position to be in is one where it creates a lot of anxiety for you. so just relax, enjoy the fantasy in a way that is not stressful for you.

experience will help open your mind. the biggest leaps in my understanding of myself resulted from being placed into new situations - moving away for school, moving to a new town for a job, breaking up with someone and moving into a new apartment - it doesn't necessarily change you, but it pushes you out of a comfort zone and accelerates your development. well, that has been my experience. you meet new people, get exposed to new things, and hopefully you get a better sense of yourself along the way.

best of luck!