One of the easiest ways to lose weight is to activate gut stretch receptors, GLP-1, CCK, PYY, and reduce Ghrelin. I'm definitely not a vegetarian, but eating 1lb / 0.5kg of low oxalate vegetables + oily fish for lunch smashes your hunger. Very fulling + low calories = sustainable weight loss.
@ElieJarrougeMD Absolutely agree - the comments on here totally miss the point. Also, the whole dieting advice is based on an error - lose "weight" is a massive error. Dieting should only be "lose fat". Keep your muscle, bone mass, brain mass, skin and hair, etc and only reduce fat
If you try something and you're not successful at it, then what determines if it is a failure or not is your choice. If you give up then, yes, you failed. If you keep trying then, no, it was a test on your way to success.