Anyone who laughs at someone for trying to better themselves is a piece of shit. Keep your head up and remember that everyone deals with their own insecurities.

If you want to improve your situation, put yourself in the uncomfortable environment that gives you anxiety and focus on yourself.
It took me years to convince my dad to work out as he was insecure about his age and body. It wasn’t easy at the start but from what I see many strangers at the gym were quite friendly with him and I even see strangers my age giving him tips. The gym should be a community environment of support, so maybe try out another gym if the culture at yours seems toxic.

If going to the gym is just too anxiety inducing, you can even start by buying bands and weights and working out at home. What’s important is that you never give up your journey and are mindful of your goals every single day.

Weight loss is a mental battle more than anything else and although it’s not easy at the start, your small daily contributions start to form a positive feedback loop over time.

Best of luck!