If it was exactly that, then fasting would actually be the perfect way to lose weight. Want to lose weight? Intake no calories whatsoever, and exercise like a fiend. Burn, burn, burn those calories, and don't add any more. And yeah, you'll drop the pounds.
But you'll also, very likely, put them back. Because starvation mode is very real.
I, too, did liquid dieting, many years ago. And I lost weight. I kept it off for maybe a year, then gained it back and more. By the time I was ready to start, it was years later and, yes, it didn't all come back in one shot. I don't blame the liquid diet for that. But starting last year was not started at 220 or so like I was when I started the liquid diet. It was 346. It was not a pleasant place to be.
BTW, at 346, I walked 30 minutes/day and ate as a flexitarian. That part did not change when I began losing weight.
I did it with the following:
* restricting myself to 1800 calories/day. Not 0 and not 400 (which is what I had on the liquid diet). 1800.
* tracking my food so as to make sure I conformed to the 1800 standard.
* eating a variety of foods and nutrients. This includes fat. Eliminating all fat from your diet is not a good idea; there's a reason why we eat it. It's for satiety and flavor but also for things like skin, hair and connective tissue.
* more exercise, including weight training. I do more cardio now, too. Before I started, I did about enough cardio to maintain. Now I do more cardio, which is to burn calories. Weight training is to build muscle, and muscle is heavier and denser than body fat, but it also kicks up your metabolic rate. Hence someone who cannot exercise much is by definition not going to have a metabolism running like a freight train.
* cutting salt drastically and essentially following a DASH diet even though my blood pressure is excellent. Salt helps you retain water and that weighs more than 0.
* cutting processed foods and not eating out as much. Processed foods are often cheaper and usually easier to make. It is easy to fall into the trap of eating them and, frankly, time doesn't grow on trees. But cut them you must, as they have lots of hidden salt and fat and less nutritional content than fresh food or at least foods you make yourself. You need to know what you're eating, which goes back to tracking.
* taking a weight loss drug, alli. It is not for everyone. It has probably only helped me lose about 15 - 25% of the weight I have dropped. Its main virtue has been in keeping me honest about what I put in my mouth. You can't lie to alli. I could have done this without alli but it helps to have a lot of good early success as it gets and keeps you motivated.
* examining my reasons for overeating. I was a really mindless eater, finishing a bag of chips and wondering how I'd done that so fast. I am now a lot more conscious of what I consume. This is a habit that's very hard to unlearn, as are a lot of habits of the obese, such as emotional eating or marrying food to socializing. This is introspection and it's not easy. Knowing yourself is, I feel, important.
* drinking water. Not only do I drink water rather than a lot of milk (I have 1 c. milk/day; used to have more like 4) so I save calories, but I also drink more of it in general. It makes it easier to exercise and it helps with feelings of fullness. It also helps because thirst is often confused with hunger so if I drink 0 calorie water (or minimal calorie flavored water), it's better than having a muffin. Plus eating better means more fiber, and that can smack you with constipation (sorry to be icky, but it's a fact). Lots of water means it all flows that much more smoothly. And that means (a) you can eat better and (b) you don't feel so bloated and crampy that you don't feel like exercising.
Yes, I've got caloric restriction and extra activity going on, but those are not the only things happening. This is not a simple system. It is a system as complicated as the weather. But it can be done. For me it's been amazing. But for others, mileage may vary.
The bottom line is less in the losing, it's in the maintaining. Only something like 5% of all people who lose weight keep it off for a significant period of time (I believe the standard is 5 years). I want to be in that 5%, and that's even harder because of all the weight I've lost and have to continue losing. I mean, my current weight is your overweight! And I have another 76 or so to go! It is not easy, and it has to be worked on every single day, for the rest of my days. I am not saying it is Sisyphian, but this is not a matter of do this once and you're all set. This is a chronic process, to be repeated daily, hopefully for another 40, 50, 60 years.