I have personally lost 5+ stone to regain a healthy weight and kept it off for the last4+ years. I have one healthy weight child despite reduced mobility and a medical diet that adds an additional 300odd calories a day.
However I have one overweight teen.
Her attitude to food was always problematic. From a young age She had trigger food that she would sneak into her room not constantly but when she was unhappy. Her relationship with her dad was a disaster after every troubling incident the food would disappear. So i stopped stocking that food in the house. She tried and absolutely hated counselling. Mostly it didn't matter because she had a competitive sport she did to a high standard. Eventually she was able to stop seeing her dad and things settled right down. There was a few years relative peace.
Then she developed physical issue that stopped the sport and she went to secondary. She had 18 months of pretty much physical hell. She still has difficulty doing any sport (especially ridiculous PE lessons) and is in low level pain a significant amount of the time. Walking to and from school simply wasnt possible (It's a long walk).
Slowly the situation was improving with swimming at home. She gained a bit of weight but not too much. Other than the low level pain and school sports she thought she was mostly fixed.
Then she attempted DoE. Her original health problem resurfaced and she self harmed that night on her early return. GP refered her to CAMHS but she wasn't serious enough for CAMHS to be able to offer anything. She hated the whole thing and promised not to do it again.
Then the eating went haywire.
She was eating a balanced diet at home, it was pizza and whatever sweets/cake her friends bought in at school. Which left her hungry, so she was nabbing tins of tuna, microwave pouches of rice at home without my realising (just thought I hadn't got as many as i thought). She'd offer to walk down to the corner shop to pick up bread but whilst she was there she pick up massive bars of chocolate too. Every now and then I'd go clear out her room to check out the extent of the problem. Pocket money was kept minimal. Holiday time was better she'd lose as the low impact exercise increased, then school shed gain. So whilst bad it didnt seem too out of whack.
Overall things were slowly settling down. I'd got her in on my swimming gym membership and we were going frequently after school.
Then lockdown hit.
She was very worried for medically vulnerable DS. She started gaining, which made no sense as neither DS or I were. Then i realised the covid stash of full fat rice puddings for DS medical diet were severely depleted. A whole large box of heroes chocolates disappeared. I searched high and low couldn't work out where I'd put them. When eventually I found those in her room there was a bit of a breakthrough.
She happily diets with me if its a meal replacement so she doesn't have to think about food at all. That's almost a relief to her. And thanks to covid introducing some major lifestyle changes on my part shes walking home from school with me despite the pain. She even volunteered to walk in solo the other day although she made it (first time since she first started secondary) this proved a step too far yet. But we're getting there slowly. Baby steps. Her room has remained entirely clear and she hasn't self harmed. DS no longer goes to DDs school so i think that's a relief too.
Being at a healthy weight involves a healthy mind. Sometimes that needs work before you can sort the body. Judgement doesnt help.