Hi,
I've lost weight in the past by following Slimming World and at its core its easy to follow: a certain amount of fibre and dairy, low fat food and limited treats. With Slimming World you have to plan ahead though and sometimes I found it difficult to eat on the go - eg if I needed to grab a lunch from a shop and I'd already had wholemeal bread at breakfast, or if I was out for a meal. And you do get used to massive portion sizes which meant for me, a day off plan was REALLY off plan.
I've also lost weight following SW principles but not rigidly eg substituting "free" pasta for a controlled amount and maybe having the odd orange juice. Was more flexible but the losses weren't as fast/great.
Now I've lost just over a stone in just over a month by being quite hardline: light breakfasts (plain yoghurt, fruit, herbal tea etc), light lunches (scrambled egg, seeded bread, omelette, small jacket potato), whatever evening meal my family are eating (which is usually well balanced but I don't get too worked up if it's a bit on the heavy side). I've had the odd cake/ice cream - but only if I'm fairly certain it's been an otherwise "light" day. I haven't been snacking much except for fruit. (I've had the odd pack of mini cheddars). Over the last month we've had father's day, I've been out for meals, we've had family birthdays and I've not been harsh with myself - just made sure I averaged it the day before/after. The biggest change I've made is no white bread as I think it just sets off cravings. I don't really drink but might have the odd G&T - definitely not wine or beer. Oh and I don't bother with low fat spreads/mayo etc - I have the full fat version but a tiny amount.
Not saying I've cracked it - I'm only a month in and I have a history of being able to lose weight very well, but I never maintain. This time I feel like something has clicked - there's no magic solution and I have to change what I eat forever. But, I am finding this routine and it's simplicity quite easy to stick to. I'm keeping breakfast and lunches simple. Very few snacks. No white bread. Hardly any alcohol. Making sure any overly-indulgent days with a light day. It's not complex, I don't really have to plan too far ahead.