Neck fat/loose skin what to use to tighten? (photos)

Your photos demonstrate a beautiful face, with excellent skin and nearly no fat under the chin. At your age and with your skin, I would recommend two procedures:
(1) Small chin implant - this can give more proportion to the chin and help create better lines in the neck. It is placed through a hidden, small incision just under the chin.
(2) Energy treatment - Ulthera or other radiofrequency treatments (like EndyMed) can help to tighten skin and underlying tissue.  
With this combined approach, you should notice a subtle difference in your neck but look completely natural.
Hope this helps! Best, Dr. Cabin

"A combination approach would give the most improvement. Nonsurgical options such as Kybella, PDO NovaThreads, and Ultherapy do well in combination for skin tightening, but the results are mild compared to surgical options.

I would recommend a VASER Hi-Definition Liposuction with ThermiRF, Renuvion (J Plasma) and InMode BodyTite to contour and tighten the chin and neck. A neck lift can be performed at the same time, if you're a good candidate. I suggest seeing a board-certified cosmetic dermatologist to develop a personalized treatment plan that works for you. Best, Dr. Emer.​"

Thank you for your question. You have beautiful facial features but you would have an improved appearance if you were to have a chin implant or genioplasty. Both procedures can be performed in the office and will greatly improve the appearance of your jawline in both a frontal view and lateral view. Unlike fillers which are not permanent, a genioplasty or chin implant is a permanent solution and does not need further or repeat treatment.

From the limited photographs presented, there is very little if any fat in the neck, and the skin tone is adequate. There appears to be a weak and recessive chin profile for which a chin implant can improve. A small  silastic chin implant can be placed through an incision under local anesthesia as an outpatient procedure. This will also help stretch the skin in the underneath the chin as well somewhat. For more information and many examples of chin implants, please see the link and the video below

Thank you for the photos and from them without an examination you would benefit from a chin augmentation.  So go on some complimentary consultations and be evaluatedDr Corbin

you are young and beautiful. You are beginning to see the very beginnings of a process that will last the rest of your life which involves the gradual loss of the elastic properties of the skin.  YOu can throw money at it now which in all likelihood will not help much, or you can wait and do something later on.  The reason to wait is that at least now there is little that can be done. A chin implant will give you a stronger chin, it will not do much for the downlooking neck skin folding. Lasers and other devices simply do not help more than temporarily.   Your choice, but I would opt for not doing much

 Hi, looking at the attached photos, your chin is very weak and there is a very slight amount of loose skin below the chin.  For over 30 years, I have performed many Chin Augmentations using silastic chin implants.  When the chin is weak, this  creates an imbalance making the nose appear larger, the mid face top heavy, making the lower face look appear short, while de-emphasizing lip fullness and allowing early formation of a "double chin".  Chin augmentation using a silastic chin implant will add projection to the chin creating harmony and balance to the lower face. 
  I place the silastic chin implant, through a small curved incision under the chin (also allows excess skin removal) to be very safe, quick, highly effective and far less invasive than a sliding genioplasty.  I perform chin implant surgery in 30 minutes or less, often using a local anesthetic alone.  In my opinion, you are a good candidate for chin implant surgery.   In contrast, any localized or topical method of tightening the skin below the chin will not be able to provide the required forward chin projection to correct the weak chin.  You can certainly augment the chin with precise placement of a dermal filler but in the long term this isn't as cost effective as chin implant surgery.  This is often done by my patients who are just learning that they have a weak chin, who hadn't previously considered correction with a chin implant.  I would also like to mention that despite its recent popularity, fat transfer (fat injection) offers far less of a reliable and predictable volume to correct a weak chin than an off the shelf dermal filler or a silastic chin implant.  For that reason, I do not use fat to shape the chin, cheeks or jaw line.
Hope this helps.

A small chin implant would be helpful.  Non-invasively tightening the skin with Profound would also help significantly.  Best wishes.