Abdominoplasty or tummy tuck is a surgery designed to remove skin and fat from the tummy, tighten the abdominal muscles, and tighten the remaining skin. It is a powerful and transforming surgery as you have probably seen from before and after photos. However, this surgery is not for everyone. There are both safety and aesthetic (cosmetic) considerations that will make this a successful and safe surgery or a surgery that did not meet your anticipated result or worse, caused you harm.
There are many scientific studies looking at the complications after tummy tuck associated with a high 'body mass index', which is a number that looks at your height and weight. The higher this number, the greater your weight compared to your height, and the much more likely you will have complications after a tummy tuck, some of which are life threatening.
From a cosmetic perspective, if you are too heavy, your result may not be what you were hoping for either. This is not a surgery that is designed to make a heavy person thin. The best candidates for a tummy tuck are those fairly close to their ideal body weight (within 20 to 30 lbs). Without looking at your photos, you may be a good candidate for a simpler and faster surgery that will remove any hanging skin and allow you to exercise and diet more effectively. This surgery is called a panniculectomy and it carries less surgical risks for people who are still too heavy for a tummy tuck.
Remember it's 90% diet and 10% exercise! I wish you the best of luck in your endeavor to loose weight and get healthy.