Losing weight is not simple or easy!
(If it was - almost- everyone would be slim.)
I don't think it is all about 'will power' either.
Our bodies are set up to fight weight-loss. (It could be dangerous in the wild :) where food supplies are uncertain. )
My experience :
Going on an unsupervised very low calorie diet (600 calories) for about 16 weeks and losing 3 stones. I was cold - insomniac - thinking about food all the time (I weighed and measured everything religiously) - hungry - tired but also determined.
I started utterly sure that a calorie deficit would lead to fat-burning (and that weight loss was all a matter of not being greedy).
It did work... but more and more slowly.
I fought backwards and forwards over the final pounds - though my weighed and measured food intake remained as low as always. (I was obsessive about following my own rules. A single calorie/gram over would distress me. )
Lack of calories wasn't leading to as much fat-buring as it had initially, and my body was somehow running on 'economy-mode' (apparently, this doesn' exist). My only evidence for feeling this is: I felt cold and physically tired all the time. I know that I was just as obsessive about weighing/measuring food and eating the same (too) low number of calories as before.
Like a sloth I just wanted to rest and conserve energy!
I fought this feeling and put in the same effort each day. (I walked and cycled throughout, but it felt more and more exhausting.) Perhaps if I'd employed a tiger to chase me about , a better number of calories could have been burned from my own body fat?
The weight went back on in the following 5 years - though I remained (too) calorie-focused and really tried to keep it down. It wasn't all about eating too much of the things I liked. I knew that if I ate, I'd be warm and more energetic... even though, my weight would creep up.
Some years ago I did some reading about changed attitudes to diet - and 'Keto' eating. This was a bit extreme for me but BIWI's low carb bootcamp here on mumsnet changed things for me.
(Thank-you BIWI - you are a person who really is 'worth it' :) )
On the low-carb plan she offers, I eat more calories but different things: more (MUCH) fat (butter/olive oil/cream/cheese/greek yogurt), normal protein, more green veg.
After an initial tussell with the change (loss of sweet treats) I don't get tired or cold and am never hungry... and the weight goes down.
My normal diet (even on 600 calories) was mainly carbs - especially sugar.
I now think that I wasn't particularly greedy in my past life but that I was using my daily calories on foods that don't work well in my body.
A carb-based diet made me hungry and only briefly gave me energy to be active.
Low-carb eating seems to allow much more food but is also much more satisfying and energy levels don't drop. The reading I've done confirms this.
I'm not using bathroom scales but I've dropped 3 dress sizes since I began low-carbing (this was at the beginning of menopause too) and continue to lose slowly but without pain. I'd like to be one size lower... or perhaps 2. This is normal eating now. Christmas and birthdays and feasts are my exceptions each year.