First time post..need advice.

Are you eating your exercise calories or just staying at 1200? If you aren't eating your exercise calories, perhaps you've slowed your metabolism. I understand it's pretty important to add on those extra calories that MFP says you earned from exercise.

First, don't forget that your body now needs fewer calories than it did when you started. Even fat tissue requires calories to maintain, and losing 43 lbs of it likely cut down your calorie allotment dramatically. (HOWEVER, it isn't healthy to eat fewer calories than you're eating right now for long periods of time, so please don't try that. Your body will start eating your muscles. Try something else first.)

The second thing is that you've probably gained a lot of muscle. As your body needed less protein (from your 1200 calories) to maintain the integrity of your fat tissue, you've started converting more into muscle. Muscle is heavy, so while you may still be losing a smaller fat, you're not losing weight. This is especially true if you're now lifting weights.

Third, your body is probably taxed. You've been stripping it of its energy reserves (fat), eating fewer calories than you would to maintain a healthy body at your weight (diet), and now you're pushing it to its limits with cardio and weights. Our bodies were designed to survive in the wilderness, with little or no food for days at a time, all while running from tigers. They're very good at adapting to anything you can throw at them after a couple of months, and yours may simply have adapted to your current diet and exercise regimen. Walking for an hour at 4.5 MPH or using an elliptical simply may not challenge your muscles anymore.

And finally, as lifetimes go, three weeks is a very short period of time. Adapting to the plateau by adding weights and buying the elliptical machine couldn't have happened more than a few weeks ago. Given that, losing 1 lb in three weeks is still fantastic. Now you just need to keep it up for another 15 3-weeks (that's only ten more months!). Don't lose hope!

I went to Jenny Craig many, many years ago. While going there I hit a plateau. They told me to increase my calories (including add a little more fat) for a few days, then back it back down. It worked! Good luck.

There are lots of posts on that. From what I understand of reading the posts, basically what happens is if you're losing weight and not eating back calories lost due to exercise your body thinks it's in the middle of a famine and slows down your metabolism and hoards fat instead of burning it.

Exactly. This is the "running from a tiger in the wilderness having not eaten for three days" effect. Humans are survivors. Our bodies were designed to stay alive, not to stay sexy. Your fat cells don't have brains and don't know what you're trying to get them to do. Fortunately, we can coerce them in the "sexy" direction with a bit of effort!