This might not be completely related to the main topic, but here's what I can tell from experience: my son struggled with low self-esteem due to how he looked for a long time. He was never overweight to an extent that would've harmed his wellbeing, but he just wasn't pleased with how he looked and hated going out to buy new clothes... I think he was feeling really low during the final years of high school. We supported him in every way we knew, but in the end, it was he who decided to break the cycle, once and for all.
He did it by focusing on how his body "felt" after every meal or snack. If he felt like walking was suddenly difficult after a meal, then he made a note about that particular dish and whenever we had it for dinner again, he would get really careful not to overeat. He did the same with desserts, ice cream, cakes, etc., he basically ditched them for several months. He also avoided white bread, only had it for breakfast, and tried to have his last meal of the day before 7 PM. He noticed that helped him fall asleep on time and wake up rested.
He also began jogging around three times a week together with some basic exercises like a few sets of push-ups and pull-ups, and that was it! His mood took a hugely positive turn soon after he made these few changes to his lifestyle. He never stuck to a diet plan or read a book about losing weight, as far as I know. He just focused on how his body reacted and set a goal of feeling happy for a change. Then he just traced the potential steps of what would it take for him to stop feeling angry with himself all the time, and, as it turned out, he knew himself better than anyone else 