Use that feeling as motivation for next time. And remember only you have the power to eat when you want. Nobody can force you to eat. The key in your situation is to be strong and stand up for what you believe in with your family. I understand not wanting to be wasteful, but it’s not like there’s food shortages right?!
I think that you should try OMAD (one meal a day) eating at a deficit. It’s much easier. If you stay consistent, after a while you will find that you don’t even feel hungry until around the time that you eat each day.
As far as finishing the plate or not being wasteful goes, to get out of that habit:
Since you know that your family members are not able to support your goals at this time, don’t expect them to. Find other things to do to distract you from eating when you shouldn’t be eating. All you have to do is just get in the habit of resisting. After a while it becomes second nature. If for example your family members are all eating (not a meal time) and you are not supposed to be eating, go take a shower, or brush your teeth… do something… anything to distract yourself. Also, next time, you feel tempted to eat the last _______. Don’t eat it right then. Put it up in a storage container, put it in the fridge and ask everyone not to eat your piece. If that won’t work, put it in the freezer (in the back where no one looks, lol).
Finally, join groups like this one and post often. You can find support here or with Facebook groups (if you have Facebook). Don’t give up. You can do it. You know the old saying… if you don’t at first succeed, try, try again!
I like fasting because I simply can’t tell when I’m hungry physically and when I’m hungry out of boredom. Good luck only eating when your stomach tells you on a daily basis. I know I can’t do that. I do however know when I’m truly hungry at the end of a fast because the hunger is so loud it gets in the way of normal daily interests and doesn’t go away.
Never feel down on yourself for breaking a fast. We are all human. It gets easier with time and attempts.
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Going outside of what your family does is difficult when living with them. They are likely pushing you because they don’t understand fasting and think it is an eating disorder. This is not bad, they just don’t understand. Explaining may help, but it may be easier to go to IF for the time being.