Will be boobs get smaller or perkier if I lose weight and tone up?

Loosing weight can influence the size and the shape of your breasts but it is unlikely to make them perkier. If you do loose a significant amount of weight and this is lost from the breast it will likely make your breast smaller and possible more ptotic. I would recommend a review with a plastic surgeon to provide you with further information. Good luck.Dr Guy Watts

It’s difficult to predict what the final results of
weight loss will be on your breasts, because each person carries his or her
weight in different parts of the body. Given that your goal is to lose
approximately one-fifth of your body weight, it’s unlikely that your breasts
will remain the same size, and you may lose some volume. Significant
fluctuations in weight can leave behind stretched skin, which can cause breasts
to droop instead of becoming perkier. However, at 17, your skin is young and
healthy, and it’s possible that any sagging is minimal. It’s also possible that
your breasts are still developing. I encourage you to pursue your weight loss
goal through a healthy diet and active lifestyle, and then see how you feel
about your breast size. Best of luck.

Breasts
typically reach final development by the time a woman has reached her late
teens, although the timeline varies from person to person. Breasts generally
stop growing 4 years after a woman’s first menstrual cycle. Given your age,
it’s difficult to predict how weight loss will affect your breasts. 13 kilos,
or 30 pounds, is a significant amount of weight to lose, and one of the
possible side effects is that your breasts could get smaller. Everyone is
different and each person’s body carries weight in different areas. Regardless
of how it affects your breast size, losing weight and getting in shape are both
steps that will help you to look and feel healthier. Once you’ve reached your
target weight, you’ll have a better idea of whether you want to move forward
with breast enhancement.

Unfortunately most people find that their breasts tend to loose volume after weight loss.  Your breasts are unlikely to get perkier after weight loss.  

Most people lose volume in their breasts when they lose weight. I would recommend that you work on your weight loss, and when you have been at a stable weight for at least 6 months, evaluate your breasts. First you should get professionally fitted for a bra. If that doesn't give you the desired result look for a board certified plastic surgeon.

Depending on how much weight you plan to lose, you may find that the breasts will decrease in size and/or become more ptotic (sag); breasts generally do not become "perkier" with weight loss.   Best wishes as you reach your goals.