Dear Beerboep
I apologise for only answering your question today, but I had to have an operation last Wednesday, and although I informed the boffins who administer the Message Board, they failed to block incoming messages while I was in hospital.
You can probably use meal replacement diets with relatively good results, provided the meals that are not replaced do NOT contain excess energy (don't overeat). You may also find that drinking a meal replacement for days on end is very boring and then stop your diet.
To lose weight you need to basically change your lifestyle. Reduce your energy intake by eating an energy-reduced, low-fat, high-fibre diet (click on 'Diet' at the top of this page, 'Weight loss' , ‘The right approach' and then on 'Slimming Diet' for a copy of such a diet), and increasing your energy output by doing regular exercise (running, jogging, skipping, cycling, swimming, join a gym or Walk for Life). While you are on the ‘Weight loss' site, read about every aspect of slimming (Diet pills, slimming aids, psychological aspects, etc) by surfing on this site.
Best regards
DietDoc