Will a Brazillian Butt Lift Make Legs Look Shorter and Thicker?

Thank you for your question. To provide a valid medical opinion I will need to see pictures of you body from different angles. I would suggest to be treated by board certified plastic surgeon with experience in this procedure, to get the best desired results.
Respectfully,Dr. Emmanuel Mallol Cotes.-

The illusion of the Brazilian Butt lift is that the extra volume is strategically placed to enhance not only the size, but the shape.  This elevates the buttock contour so that the lower back contours are tightened and the length from waist to floor is lengthened.  This has the effect of making your legs "longer".  Try a small towel positioned below your waist on the upper buttock area.  Compare your lateral profile in a mirror with clothes or jeans.  Speak to your surgeon not about size, but about this position and the shape desired.

Hi 4423Anon

There are many rumors about liposuction and the Brazilian Butt Lift.  One of the most common is that the fat can move to other areas.  It does not.   Your body is solid and tissues and organs cannot just move around. 
Where ever the fat cells are placed is where they stay. 
I do not believe that this procedure will make your legs look heavier.  If anything, it will probably make them look smaller. The bigger your buttocks is, the smaller it makes your waistline and thighs look.  If you think your thighs are too large, then liposuction may be an option to make them smaller too. 
The  most important thing with this and any surgical procedure, be sure you choose a Board Certified Plastic Surgeon who has lot of experience with this procedure.  Good luck