One thiong I did to start the process was change out my suual breakfast sandwich (egg, ham and cheese) with oatmeal, 2% milk (pour milk over oatmeal) and two slices of whole wheat toast, unbuttered but with a little jam. That change alone, and not changing anything else, rejumpstarted my metabolism and I am not only down 20 pounds in about 8 weeks but my cholesterol has taken a nosedive and is down nearly 50 points. Now, I do ride about an hour a day 6 days a week but prior to that I have also done a lot of walking.
What is necessary is to not find a "diet". You need to change eating habits, not diet, or you won't get the results you want...a diet is to hard to stick to. Make small changes...drink 2% milk vice whole or even better, skim milk. Switch to wheat bread vice white. Even though the going number is 8 glasses of 8 ozs of water per day, even adding a single glass per day will help. If you drink juices or soda, substitute a glass of water instead...juices, while we may think they are healthy, are actually pretty high in sugar. It is important to lose weight gradually and alittle at a time rather than trying to drop a lot in a short amount of time..your body adjusts much better and won't feel like it has to slow the metabolism if the weight comes off gradually. The going "heathy" weight loss number is just a pound and a half a week. That equals out to cutting just 500 calories per day and working out, however you choose to do that, at just burning 250 calories per day, which is easy. Remember, muscle burns calories which is why workikng out and getting that muscle is so important.
Best of luck...I have fought with my weight my entire life and have hit all of those highs and lows.