There is no such thing as vanity weight

There is a certain weight range for optimal health, and if you’re a little flabby, then it is beneficial to trim it off.
Generally speaking, it’s pretty rare for a person to
need to eat less, unless the person is already obese, in which case their body will give them signals for hunger even when it isn’t necessary to eat. What they need is A) to change what they eat, and B) physical activity: aerobics and/or strength training.
It isn’t explicitly sinful per se to throw food away but it should be avoided. Readjust meal plans and get a better estimate of how much you eat to reduce the burden on your wallet, or on your parent’s wallet. Eat until you’re adequately full and then stop eating. Simple as that.
Sometimes people get confused about what a normal portion meal is. I’m a 30-year-old man in peak condition and my overweight mother gives me weird looks because I haven’t porked down 3 plates of food. I eat one plate of spaghetti with some veggies on the side and a tall glass of water and then I stop eating, and she looks at me as though I’m sick or something. I don’t know why she has the idea in her head that shoveling gratuitous quantities of food down your throat is suppose to be normal, but mindsets can be hard to break. She was raised with the notorious “There are starving children in China” philosophy, which is nonsense in relation to what you should or shouldn’t eat in a given moment. Most freshly prepared meals degenerate within 1-2 weeks. If you’re full, then stop eating.
People aren’t starving in the world because there is too little food. There is a vast superabundance of food. People are starving because of infrastructure & distribution & communication.