I always tell to my patients that the only way to preserve the results of cosmetic surgery is through a healthy lifestyle that includes healthy eating and good physical activity. However, after an operation it is important to be careful when resuming an exercise routine.
Your return to GYM will depend entirely on the type of surgery performed and your condition. If your recovery remained normal, you can start aerobic activities after 30 days, such as walking, aerobics exercises and the like.
If it was an ABDOMINOPLASTY, you will not be able to perform sit-ups for a long time (from 4 to 6 months).
If you had a breast lift or put on a prosthesis, you should not make physical effort with your arms. You can work the lower train, the abdomen, move the arms in a class of aerobics; but you can not lift weights or use weight machines for 6 months.