Can walking and talking green tea supplements help me loose weight?

i am 5 feet 7 inches and weigh 183 lbs. I know there is no magic pill that will burn all the fat away and I'm just going to start off with walking (brisk walking) for at least 30 minutes or an hour 5 days a week I'm asthmatic and i stay away from strenuous activities because of the way it makes me feel when I'm done and i do not have access to a gym :(. so I'm just asking will brisk walking and drinking lots of water everyday and taking green tea supplements help me at all?? if so can anyone estimate how long before i start seeing a little result?? oh and i don't normally eat junk food either.