How committed? means: "How important is it to you?" Lame excuses like "I can't exercise because I babysit my nephew" is what you have when you're not committed. There's always a way, if there's a will. Cliche, yes, but true. I recommend you start eating a healthy diet. Lots of lean protein (low or non-fat dairy, lean or extra-lean meat), products made from whole wheat or better whole grain (this doesn't have to be complicated...oatmeal, cous-cous, a good whole-grain bread), and try to keep your ratio of protein:carbs:fat around 30/50/20 (Meaning calories from each is that percentage,not grams of, calories, fat has 9 calories for every gram, protein and carbs have 4).
As for exercise, I recommend you start some daily aerobic exercise. Walk around for an hour every day. I don't care if you think you don't have time. Walk back and forth in the house at a brisk pace if you can't get out. Once you can walk 4 miles in 60 minutes, you may want to consider trying some jogging. Depending on your weight at the time, as it can be hard on the body. For now walking is good stuff.
Don't make excuses. If you wan't to lose the weight, find out what's healthy food, eat it. Get the exercise. Best wishes.