Probably the best piece of advice I can give anyone trying to lose weight is to always, always, always, check actual calorie counts in foods, and don't assume that just because something sounds healthy, it's actually good for you.
Case in point, McDonalds' new oatmeal offering. Mark Bittman has a fantastic piece about it which you can read here: http://opinionator.blogs.nytimes.com/2011/02/22/how-to-make-oatmeal-wrong/
Bittman did a little exploring and here's what he found:
Incredibly, the McDonald’s product contains more sugar than a Snickers bar and only 10 fewer calories than a McDonald’s cheeseburger or Egg McMuffin. (Even without the brown sugar it has more calories than a McDonald’s hamburger.)
Get that??? If you order this new "healthy" Micky D's offering, you're really not much better off then if you had gotten an Egg McMuffin or a cheeseburger. BTW, here's the nutritional info from the McDonald's website: http://nutrition.mcdonalds.com/nutrition1/itemDetailInfo.do?itemID=1500
Here's the reality, you won't lose any weight or keep it off if you head into McDonalds for your food, even if you order their "healthy" offerings. McDonalds is a big corporate giant which has made boatloads of money marketing unhealthy, cheap foods.
Faced with what it sees as a rising tide of people looking for healthy options, what does McDonalds do? Rather than actually offering healthy alternatives, it offers unhealthy foods marketed as being healthy.
A corporate tiger does not change it's stripes too easily when those stripes have proven in the past to be wildly profitable. McDonalds isn't interesting in actually offering you healthy foods that will help you lose weight. McDonalds just wants to sell you cheap calories loaded with sugar and fat so that they can make money.
So if you're trying to lose weight, and keep it off, bypass McDonalds. Make your oatmeal at home, or bring it with you to microwave at the office.