When people gain and lose weight, the fat cells in the body get bigger and smaller. Fat can be removed with a variety of techniques that have permanent results:1) Surgery can remove large areas of fat through incisions such as when a tummy tuck is done.2) Liposuction can remove large amounts of fat through small poke holes. Adjuncts to liposuction include ultrasound wave, radio frequency, laser, and power which may make the results easier to achieve.3) Noninvasive technologies that kill fat cells through topical treatments that don't puncture the skin. For example, coolsculpt does this by freezing fat cells.All of these techniques permanently remove fat to varying extents in the treated area. The fat will not 'grow back' in this area. If you were to get a treatment and then gain a lot of weight, the fat cells left in your body would all get bigger. If your outer thighs are the place where you usually put on weight, and you have liposuction to make them thin - you will notice a difference the next time you gain weight - you won't see it in your outer thighs.For these reasons, it is very important that a surgical, minimally invasive, or noninvasive treatment evaluates your body as a whole to design a procedure to gives your body balance - this helps create the best and most long lasting results.