"You don't think having it tucked in makes me look fat?"
Having the shirt untucked makes you look fat. Untucked says you're covering up or hiding something. It looks sloppy unless you're wearing a tunic style shirt that is meant to be long and worn over pants or a skirt.
When your shirt is tucked in, it gives a much neater appearance.
What makes a person look fat is when they wear clothes that are too tight. Wear clothing that suits your figure and no one will notice if you carry a few extra pounds.
I am going to say leave the shirt untucked and not because tucking it in makes you look fat. After all, fat makes you look fat, not necessarily an untucked shirt. Also, clothes that are too big or too small can make you appear fat.
If memory serves, Elaine, you are short like I am. I am 5' 2" (157 cm) and am also short waisted, meaning my lower half is longer than my shorter half. When you are short, tucking in a shirt can make you look really cut off and ridiculous. Being short waisted makes it appear even worse! :-)
I know I have a properly fitting shirt if it sits just above my hip. If I have that, I know I can leave the shirt untucked and look great.
Excellent news indeed! Elaine, I encourage you to post more items like this and less about the disgusting mukbangs and deadly fast food. You seem very pleasant when you post positive things. It's a nice change.