Firstly, if you eat less than 1000 calories a day and do an hours worth of exercise your body will go into starvation mode as it recognises that it is not getting anywhere near enough calories to function properly so it will slow your metabolism right down and will be more likely to store fat, so whilst you will probably notice your weight drop suddenly for a couple of days it will then stall completely and when you start eating a normal diet again you will put more weight on because your metabolism will have slowed down so much. Depending on your age and how active your daily lifestyle is your body needs around 1300 calories a day just to make it work, so you need that even if you are just sitting down all day and sleeping all night, add an active lifestyle and exercise on top of that and you need considerably more. There are websites which can work out how many calories a day you need roughly to maintain your current weight, I can have a search and find one if you are interested. If you want to lose weight you should only reduce that calorie intake by about 300 calories a day, any more of this and your body will start burning muscle rather than fat which will decrease your metabolism.
Now, csn I just speak up for weight training as opposed to purely cardio! Resistance training will build lean muscle which will increase your metabolism which in turn will help you burn more calories throughout the day. Also, if you do it properly and use heavy enough weights then trust me, it will really raise your heart rate as well! Try doing ten squats, ten push ups, ten lunges on each leg, rest for 60 seconds and then repeat and see how you feel. Now imagine doing that with weights. Doing purely cardio will burn some fat but also muscle whilst proper resistance training will burn fat and build lean muscle which will lead to a much leaner and slimmer physique.
Whilst you can't spot reduce the fat on your stomach, by strengthening your stomach muscles then you can help to 'hold it in'. The plank is a great exercise for your core, if you have en exercise ball then and are effeective.
are meant to be a good alternative to sit ups which will not hurt your back or your neck.
However, you do not need to be doing loads of these and everyday. If you follow a basic resistance training programme which incorporates things such as lunges, squats and press ups etc then you will see results in a thirty minute session three times a week. All these sort of exercises all work your stomach and 'core' muscles as they have to work to keep you upright and balanced.