First of all, congratulations to you on your recent improvements. Keep at it.
IANA nutrionalist, but here’s my take on it:
First of all, it depends on the kind of weight you are losing. Most likely, you’re burning off some of that extra fat you’ve been carrying around. It’s not unusual to lose quite a bit of weight in the beginning of a new exercise program, and if you’re 50 lbs overweight losing 6 lbs in a month, or even 3 in a week is nothing to be particularly concerned about. Just getting any exercise, especially muscles that haven’t been frequently used, is going to stimulate the ol’ metabolism and burn off some reserves if you aren’t feeding yourself enough to sustain your activity level. You’ll most likely plateau out once you’ve become accustomed to your new level of effort.
If you are losing water mass, it’s just temporary and either indicates that you need to drink more water or that you might have some kind of side effect from one of the drugs. (I don’t know about Concerta but IIRC Wellbutrin has diuretic side effects. I know when I took it I was always thirsty and always needing to take a leak.) You don’t really need to drink the 10-12 glasses of water sometimes recommended (you’ll get most of that in your daily diet anyway) but hey, drinking more water doesn’t hurt you, especially if you’re trying to exercise and burn off fat. It does help keep your kidneys healthy and flushed out.
If you’re losing muscle mass, then 6 lbs a month is a real problem. If this was the case you probably wouldn’t be feeling too good about walking, sit-ups, and push ups, though; you’d feel weaker, not healtier.
As with any change in lifestyle, excerise plan, diet, et cetera, you should go see a doctor and all that (or better yet a professional nutritionist, as most MDs are pretty ill-informed on nutrition), but unless your bloodwork comes in seriously abnormal I doubt he’s going to say anything discouraging at this point. The thing to avoid is the weight cycling that many people do, pogoing up and down the scale.
A few of random thoughts:
Eating a good breakfast and dinner is recommended, of course, and I don’t see any harm in your light (or no) lunch if you’re not hungry or not feeling ill effects. I see my cow-orkers bringing in or going out for huge lunches, then sit around all afternoon and get dopey 'cause they aren’t doing anything but sitting at desks or in meetings. If you think you need to consume more during the day, try eating a couple of snacks instead of lunch, or get a premixed smoothy like Odwalla or Naked (I like Boathouse Farms stuff but it’s expensive and may not be available in a store near you) and drink it at your desk (assuming you have a desk job) over the course of the day. You could also try drinking one of those canned drinks, like Ensure, but personally I think they taste nasty and I’d be afraid my coworkers would start putting “Depends” boxes on my desk, only most of them don’t have that much of a sense of humor.
Don’t get all worked up over the carbs fury that the Atkins-type people like to pound on, but do avoid the junk food (crisps and other Mylar-contained nutritional vacuums, soda/pop/coke, et cetera.) Eat a balanced diet; some vegetables, some grains, a moderate amount of protein in your favorite form, you know the drill. If you find you don’t have an appetite in the evening (and assuming you aren’t a teetotaller and it isn’t contraindicated by the drugs you’re taking) have a glass of wine or a beer with dinner, as alcohol stimulates the appetite. Also, try to eat shortly after exercising, while your body is still stimulated. (Though I find I don’t have much of an appetite right after running…it usually takes me 30 minutes or more before I can choke down a shake.)
Make sure you’re getting enough fluids, especially if you’re losing weight. I usually bring a litre bottle of tea to work with me and drink it over the day.
Keep on the exercise and try to come up with variations, or things you can do on days when it’s raining or foul out. I don’t generally care for gyms, but you might check out some near you, or look for something else you can do. It doesn’t just help with the fitness but will also keep your attitude up. (I suffer from depression myself, but I find that a nice hard run pushes the blackness back, if even only for a few hours.)
Good luck to you, and keep it up.
Stranger