Firstly you have to be careful as you have back and neck problems, so for that same reason, I would not recommend you use weights while you are doing cardiovascular work on the step or treadmill.
Losing weight needs a concerted effort in the areas of a sensible low-calorie, high-nutritious diet and a moderate amount of exercise. A good way to lose weight is to combine calorie-reduction with spending calories as much as you can.
To achieve the first, you have to eat a balanced, nutritious diet. It may not be a good idea to miss any meal as that slows the metabolism down and hinders weight loss.
To aid that process, you may like to add on ANY exercise you can manage to get. The best results are when the exercise is regular and consistent, but the good news is that EVERY BIT COUNTS! So find some way of incorporating any activity into your daily routine walking to the office, school, up the stairs; any weekend routine can also be of help.
If you want to get on a serious weight loss plan, besides commitment, you need to go in for a 3 PRONGED PLAN
1. Aerobics: You need to work on building your heart-lung (cardiovascular) endurance. Take up any activity form cycling, to running or jogging to skiing to swimming to even brisk walking to get that gut into its original size. This kind of activity will draw upon the fat stores in the body for generating fuel to last that long. The presence of oxygen (controlled breathing during this workout, instead of huffing and puffing) will mobilize the fat to get utilized instead of stored. This will take care of the fat that lies ABOVE THE muscles.
Thankfully, any aerobic activity that elevates your heart rate can help you burn fat and take off unwanted pounds. Many experts recommend doing at least three sessions of 20 minutes of aerobic activity per week. Ideally, for long-term weight control, you should engage in at least four sessions per week, for 45 minutes each time.
2. Weight Training or Yoga: Get a yoga teacher to train you in the complete area of yoga or you can join a gym or work out at home with an OVERALL weight training program so that the lean mass percentage IN THE ENTIRE BODY increases. Balance your ab crunches and leg lifts with an equal amount of effort for the lower back to ensure it is not weak. Work out the rest of the body for the best results.
And of course, concentrate on technique and quality of your ab crunches and pelvic lifts, rather than higher repetitions. And remember, exercises such as these, only improve the tone and endurance of the muscles, they don't burn fat.
3. Healthy diet spread through the day, not night: Eating the right food out of habit rather than as a fad, can work wonders for an extra middle. Keep the calories light and spread out through the day rather than bunching them all at night and then sleeping on it, when the body's metabolic rate is the slowest.