You need to step back and not do the 13 weeks for fat burning straight away. My guess is that you have little to no experience of exercising regularly and as such you have no idea what your physical capabilities are.
You have to walk before you can run. So don't rush into a full blooded workout and exhaust yourself. You'll find that your stamina (endurance) is not good. What you will be surprised at is that you'll actually be pretty strong as you are carrying your frame round daily and that requires effort on its own.
Focus on slowly building up endurance, i.e aim for 120-180 minutes of cardiovascular work a week total, spread equally over 3-4 days e.g. cycling/ walking / cross trainer. Exercise wise use body weight exercises like kneeling planks, then full planks, glute bridges, kneeling pressups, bodyweight squats. Core exercises that will help you develop core strength and posture. Even 30 minutes 3 times a week will help you get started.
Just building up intensity and then the time spent on cardiovascular work. Doing these will result in progression and potential fat burning.
Your main focus should primarily be dietary. There's got to be a 110% effort into diet as this will give you the greatest results and transformation, more than exercising will at your current stage in life. Exercise will become more important when you are at the stage of maintaining or increasing existing muscle mass and boosting your metabolism to further aid your fat loss goals.
One thing I would definitely advise is that you contact your physician and discuss exercising and dietary requirements with them before you even attempt any form of exercise. They should have knowledge and contacts which will help and advise you so that your health is always put first.
Also you mention issues. ''I want to improve my health but it is hard with my issues.''
Get the support of family and loved ones. Issues disappear when those around you support what you want to achieve. And equally don't let anyone get in your way. If you 100% want to lose weight then go for it.
Do or do not, there is no try.
Last edited by Gregsimo; 11-06-2013 at 12:19 PM.