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There's no shame in ordering food to eat. Nourishment is nourishment, whether you make it yourself or order it. The important thing is that you're getting something in your stomach. Not everyone has the time, the physical or mental energy, or just the resources to cook their own food, and ordering food is an alternative to that. You're doing what you need to do for your body and to take care of yourself.

Honestly I wouldn't blame you if you did tell your neighbors off for this! Maybe next time they start to chastise you for ordering food you can firmly remind them that what you do for food is none of their business and you would appreciate it if they worried about themselves only. What you do with your money is your business and yours alone. Tell them that if they continue to make comments like this you will not be interacting with them in the future. They don't sound like the type of people who are worth interacting with anyway unless it is something relevant to being your neighbor.

If they continue to make these comments after you firmly tell them not to, I'd try not to respond to them. Maybe they are feeding off of the fact that you are responding to them and they know that they are upsetting you. If you consistently don't answer them maybe they'll start to get bored with the whole thing since they're no longer getting that reaction.

You deserve to eat, no matter how you get that food into you. You deserve to eat whether it's a freshly cooked meal or ordered from your favorite restaurant. Honestly, it's great that you're ordering food because it means you're eating at all, especially on the days where it feels impossible to do so. You're worth it.