Liposuction should be considered as a contouring procedure, for example if your thighs bulge to the side at the top of the leg and we suction this area, the contour of the thigh will become straight instead of like an S. This allows for ongoing weight loss or gain with the new shape. In other words, your thigh circumference will increase or decrease with weight fluctuations but you will not regain the bulge.
One thing to think about is that the liposuction is a closed procedure and therefore the uniformity of the procedure is not as controlled as one would see from a procedure such as an abdominoplasty (all the skin and fat from below the belly button is removed and the remaining skin is draped downward so this flap is uniform in thickness), so with weight changes may make irregularities more obvious. Typically, this is not the case, but it is a risk since liposuction is done by palpation rather than visualization.
Most people find that any procedure that is done to help control areas of excess are very helpful in allowing them to continue to lose weight and control their weight. If you are a candidate for abdominoplasty, there is a much more impressive and visible improvement than you will see with liposuction.
The best thing would be for you to go for some consults and get some opinions by Board Certified Plastic Surgeons who can see what the quality and quantity of tissue and fat on your body. Once a doctor can see what your body is like, it will be possible for that doctor to explain their ideas on how to treat you to achieve your goals.
Remember, there are many ways to skin a cat, so several opinions are good and photos of the results of each procedure will be helpful to you in deciding which way to go. It really does not matter if you do the procedure before or after weight loss, although some doctors feel that the risks can be lessened when the weight is less. Best Wishes!