Are you sure your diet is beneficial in helping your cause?
If your going to walk make sure you walk at least at a moderate pace, obviously if you jog this will be burning more calories, but it nice to start of easy and gradually increase the difficulty.

Also, it is possible that you have lost fat and also gained muscle so the weight issue is kind of nuetralised. Its only been one week, the added muscle will help you work more effieciently, hence lose more fat.

Changing your eating habits and walking for 30 minutes a day is not going to help you lose fat unless you're on a 900 calorie diet. If you are serious about losing weight you need to show dedication and persistance for more than one week. You should be weight training intensely at least 3 times per week, and performing real cardio (not walking) at least 2 times per week. Eat no more than 10 x your bodyweight in calories per day. Do not cheat with your eating more than once per week and do not miss more than one workout per week.
Do this for 3 months then tell me what happened.

only eating and walking are not enough. it has been my personal experience that you have to cut down more things that this to really lose some weight. to reduce myself, i have cut down sugar in my tea, coffee and other other sweetened beverages such as colas as they contain large amounts of calories and sugar.

apart from that i stopped taking one meal of the day, i take a healthy breakfast and a nice dinner as i cannot sleep on an empty stomach. i have stopped taking lunch and in its place i take digestive and sugar free buscuits along with something light like fruit or tea.

also, green tea with a liberal dash of lemon is vey good for burning fats. try this out, as this may really help you in losing weight....

my tummy went in within a month and i have benn hearing ppl say that i have gone slim.