Seven pound weight gain 3 weeks post-op Tummy Tuck with Lipo

Congratulations on having undergone the tummy tuck surgery. Yes, it is quite normal for patients to gain weight after surgical procedures. Patients tend to retain fluid; it may take several weeks for this fluid to “mobilize” and for patients to return to their preoperative weight. For more precise advice, continue to follow-up with your plastic surgeon.  Keep in mind, that it is also quite common for patients to go through significant emotional "ups and downs" during their postoperative course.Best wishes.

Following plastic surgery and especially surgery around the soft tissues of the abdomen it is not uncommon for tissue to retain fluid. This may be even more likely following combined liposuction. Proper diet following surgery is important as well. Close follow up with you plastic surgeon at this time is a good idea.Post operative results continue to improve for months and are optimal at 3 to 6 months

This is due to healing, swelling, and ultimately water.  Humans are 60% water by weight.  Swelling after trauma or surgery will cause our body to store more water.  Additionally, expect this not to resolve until a period of 6-12 weeks.