How much weight could a 250lb woman REALISTICALLY lose in 5 months?

I'm about your weight. Over the past 90 days, these are my stats taken as a straight average, and being ruthless about tracking. (Including holiday eating, mind). Exercise calories may be a little high on the estimate. At least, I think so, but it's what I am recording, even so.

Daily calories: 1772 eaten
Calories burned through exercise: 321
Weekly weight loss: 1.1 lbs

My exercise is lap swimming (training for a couple of open water swims this summer), which I do a minimum of four times a week, but more like six most weeks for between 35 minutes and an hour, depending on training schedule.

So, a five month goal of losing 20 lbs is more than reasonable. Chances are you'll do better than that.

Keep in mind that generally speaking, you can't out work a bad diet.

I think you could lose 40 lbs. if you really push it. Good luck!

50 lbs is not unrealistic my starting weight was 240 and I lost my first 70 lbs in 7 months so average about 10 lbs a month, but I was on point with food and exercise!!

Not only boot camp, but a nutritionist as well..40 pounds.

I'm hoping to lose the same amount in that time. I weigh 269.

20-25 is realistic, 40 is possible, 50 is rare.

Given that you are starting at 250 pounds, I could see you losing 60-80 pounds in five months if you're 100% dedicated.

I lost 70 pounds in five months. I started at 230, and after five months I was down to 161. I've gained weight (muscle) through strength training and I now weigh 175, but more than a year later I've kept roughly the same bodyfat percentage that I had at 161 pounds. I understand the value of losing weight slowly (to give you time to learn good habits), but honestly I don't see the NEED to lose slow if your goal is to simply lose weight.

Maintenance AFTER losing weight is actually a heck of a lot harder than just losing weight. After you've lost a lot of weight, you then have to overcome old habits, old demons, and figure out a new way to live the rest of your life at a healthy weight.

Losing weight is simpler than maintenance because you are focused on a task with a goal, an endpoint, and milestones, and those milestones keeps you going. Maintenance lacks those same visible milestones, and thus it is much harder to define and rally around.

So I say how FAST you lose weight isn't important for psychological reasons, though it may be for physiological reasons (keeping muscle mass is easier if you set up a smaller calorie deficit). Instead, just lose the weight as fast or as slow as YOU want (it's going to take months anyways, and that's long enough to develop good habits). The idea that people get sick or risk their health from losing weight too fast is basically an old wive's tale. If you're eating at least 1,000 calories a day and getting essential nutrients, and are suffering no ill effects, you will be just FINE... you're not gonna die losing 2-3 pounds a week. I've heard of plenty of people dying from obesity... never heard of someone dying from losing weight if they're still getting 1,000 calories a day and essential nutrients.

As for how MUCH to eat, I recommend ignoring the MFP calculator. Instead, find an online TDEE calculator. At 250 pounds, if you exercised 3 times a week, you should need about 2,500 calories a day to remain at the same weight. So I would reduce your intake to 1,500 calories per day, and you should lose about 2 pounds a week to start, and probably a lot more in water weight as you eat healthier foods and less salt and junk food. Want to get more extreme? Walk 2 miles every day, work out (lift weights or aerobic exercise) 3x a week, and eat 1,000 calories a day (the minimum I would recommend), and you could lose 60-80 pounds in five months. It IS possible. Don't let people tell you it is not possible. It IS possible. I've seen it done just like this many, many times on this very website. And I lost 70 pounds myself in five months, so I am also speaking from experience. I've also kept it off, so I was able to debunk the myth that you're destined to put it all back on if you lose weight too fast.

Reach for the stars. Getting married is a huge deal. It's the single greatest day of your life up until now, so you have a very good focal point in the coming months. When you get hungry and want to binge, or get tired and want to skip exercise, just think of your wedding dress being a bunch of sizes smaller. It will be worth it.

Good luck!!