Does liposuction to the buttocks have any side effects?

Of course the answer to this question can only be made after evaluating your particular anatomy, defining and communicating your goals, and developing a plan with your surgeon.  Every person, regardless of their heritage, has a different anatomy.  They also have different goals.  In addition, every surgeon has a different quality of education, training and experience.  If you choose a surgeon who hears what you want, has the skills experience and techniques to achieve your goals, and designs a surgical plan based on your individual anatomy, you will get the best outcome.  

The fat of the buttocks is supported by a matrix of connective tissue. Liposuction can make the area look ptotic or droopy

Liposuction of the buttocks may injure the connective tissue attachments from the  skin to the underlying muscle. This may cause the buttocks to sag.

Liposuction is commonly done in the flank area above and around the buttocks to decrease the fat in the love handle areas and make the buttocks appear more attractive. In certain American African women, who have large buttocks, liposuction in that area can achieve a good look. In most Caucasian women, it will give them a flat and saggy butt. Most men tend to loose buttock fat with aging, and usually is not done on men. So, usually liposuction is not done on the buttocks in most people to avoid sagging.

I almost never recommend liposuction of the buttock.  Certainly bulk can be reduced in the buttock with liposuction but the previously smooth skin of the buttock can become very irregular due to the dense connective tissue and  compartmented nature of the fat of the buttock.  This effect tends to worsen with time.  Best to talk to several plastic surgeons experienced in this area.