Congratulations on willing to do something to improve your health. Please for your sake and that of those that love you keep it up.

You asked how long should you expect before something starts happening? That is a reasonable question. I'd answer that something already is, you may just not visibly see it yet.

Weight control, despite all the rhetoric out there to complicate things is really very simple. Calories in vs calories out. Your body has a basic need for energy which it produces by metabolizing food which you eat. The more energy you use up, the more your body will burn in terms of food. If you take in more than you burn up, your body stores the excess as fat. If you take in less food than you need to burn up for energy then your body will resort to the fat stores or your mucscles for the energy it needs to sustain you. Simple, intake vs output. Do not be confused with all those that complicate the issue by saying the body metablism adjusts, you are big boned, you need to eat high protein, you need to eat low carb, yada yada yada. Eat a balanced diet, as low in saturated fats with as little processed foods and as much fresh natural foods as you can and you will be ok. Moderation over time is the key. The last thing I will say is that diet is not a 'quick fix' that can be abandoned once you reach your goal. Diet has to be a lifelong change in how you approach eating and exercising. Keep both in balance and you will reach a stable healthy body proportion.

Assuming that your commuting is entirely new added exercise you can expect to be burning something around around an additional 400 calories per day (lots of assumptions there, but in the ball park). If you keep your intake to what it was prior to beginning commuting, then you could expect to lose approximately a pound a week. Yes, you will build muscle which is denser, but your rate of building muscle will be less than your rate of burning fat assuming you haven't increased your food intake. That is the key, keep your food intake lower. If you aren't beginning to see some progress within the next several weeks try to cut down on your food intake. I would bet that is the culprit.

Again, remember that you didn't get 30-40 pounds overweight in a matter of weeks, but probably over a number of years. You won't get rid of that excess weight in weeks either, it's all about long term change. Keep it up and I promise the change will come.