About two months ago I started running. Nothing heavy. Usually 15-20 minuntes as part of my workout 6 days a week. I got sick a few weeks back, and lazy during christmas, so I stopped running during this time(about 2 1/2 weeks), but still managed to do everything else.

I realized during this time I started dropping weight rather easily without changing anything else in my diet. I'm wondering if I was losing muscle mass, or now that my body isn't adapted to running, its not holding onto every calorie for energy.

Just curious because I don't want this to hinder my loss efforts. And if it is effecting how fast I lose, do you have any suggestions as to counteract this?

Oh and I do realize its just a number on a scale, but I don't want to start really building serious muscle mass until I hit my goal, then maintain, so I would still be losing fat, and replacing it with muscle . Which is why i'm choosing to wait to weight train

I eat 1500-1600 calorie a day....hmmmm Maybe on the days I run I should play around with the amount, uping it another few hundred. And on my rest day, sticking to my usual amount...I'll try it for a week or two and see what happens

There are 2 great sites on 3FC that I can recommend you scan for info relating to this topic:
January Running
Running FAQs

Hope this helps you! & Great Job on running!

My losses started to slow up once I started running, and my appetite was RAVENOUS!!! I definitely think running has something to do with that. On the days I run, I do up my calories a little. Otherwise, I'll end up binging.

That's funny: I've always heard that running is a calorie scorcher and helps one lose weight.

Well, I should also say that I started running once I was at 200lbs, and my weight has been dropping a lot slower than at the beginning. I don't think that is necessarily related to the running. I think it is true for everyone once they only have 20lbs or less to go.

Actually, it's next to impossible to build muscle and lose weight at the same time. To build muscle, your body needs extra calories, where (as you know) to lose you need a calorie deficit. That's not to say you can't get stronger while losing weight, because you definitely can, but you aren't going to "bulk up" while losing weight.

That said, keep running if you enjoy it. It's a good calorie burn. You didn't say what the rest of your exercise routine was, but I would recommend some light weight training. It helps you maintain lean muscle mass while losing weight.

Personally, my weight started flying off once I started running.

I have been running for nearly 5 months now, I run 6 days a week usually between 3-4 miles each day. When I started running I found the pounds actually dropped off but then it started to slow after 2 months, this is natural as your body gets used to a exercise it learns to do it more efficiently thus burning less calories. I found that I had to switch up my runs, 2-3 days a week I do interval training, the other 3 I try to alternate between going for speed and going for distance. I also found on the days I do intervals I need a protein shake after and the other days I need to actually eat slightly more complex carbs without acting eating more calories, I keep my range between 1200-1400. The pounds are still coming off relatively fast for me. There really is a sweet spot though, when I change my eating or running routine everything goes haywire lol

I initially lost weight faster while running. Then, as my body got used to it, it became about the same as any other cardio

Running is not some magical calorie hoarder.

In all likelihood you either
a) DID change something in your diet and didnt realize it
or
b) You shed the water weight that your muscles were holding on to since you hadnt been running very long and were still adapting. This kind of loss will stop after 2-5 lbs usually. And isnt specific to running.
or
c) you had hit a plateau for awhile and moved off and the timing was a coincidence

While you may have built some muscle during the time you were running it is unlikely to have been much (contrary to popular belief you CAN build muscle from running - just not as effectively as with weight training) and you are unlikely to have shed that muscle in a 2.5 week break at the weight and calorie level you have unless you were on a supremely low protein diet.

If you are on a low carbohydrate diet it is possible that you shed some glycogen stores during the time off and the water stored with it.

There is absolutely no reason to think that at 1500-1600 calories you can't incorporate 15-20 minutes of running. Adding a few hundred extra calories will be way more than you are burning in that exercise and WILL be counter productive.

While there is SOME merit to the stress hormones argument it is HIGHLY unlikely that 15-20 minutes will impact it.

While not addressing your original question waiting to weight train "so you dont build serious muscle mass" is not terribly productive. You arent likely to put on SERIOUS mass while losing and you will lose faster and look better if you incorporate it sooner. Plus, correctly done, weight training can support your cardio efforts so you dont get injured as easily.

running has been a major factor in my ability to lose weight...and i don't even "run" like some ppl put in miles a day...im not able to do that yet

i spend 45 minutes on the treadmill every day except sundays...i do intervals of 3 minutes running at 4.7 mph and then a minute of walking at 3.0 and i do that for half an hour, totally about 20 minutes of running...then i push the incline up to 15% and walk at 3.0 for another 12 minutes, spend a few minutes cooling down, and i'm done

i try to keep my calories around 1200-1400 and i don't eat back what the treadmill says i've burned...i try to make healthy choices with my calories as much as i can...

this routine has really helped my body get in shape over the last few months and drop weight...i weighed 211 when i began in october and i'm at 199 as of today

"There is absolutely no reason to think that at 1500-1600 calories you can't incorporate 15-20 minutes of running. Adding a few hundred extra calories will be way more than you are burning in that exercise and WILL be counter productive."

I should have been more clear in my original response. I do think I may be eating to few calories, which is one of the reasons I was considering increasing it. My BMR at a sedentary lifestyle is about 2100(because of my height), and doesn't include how much I move around during the day, and how much I burn off exercising. Because of this I know I created two high of a calorie deficit and my body has grown used to how few calories I've put in it. From what I understand, I need to increase the amount I eat, and up the intensity of my exercise to kinda get back on track. Sorry for the unclear original post... And it may have been a plateau that I moved off from like you suggested. I hovered around 200-197 the entire time I'm hoping your right on that The weight dropped off pretty quickly more so then what I'm use to, which is why I got a little worried

As for incorporating weight training, I'll talk to a trainer at my gym tomorrow and see if he can help me come up with something, because I'm 100% completely clueless when it comes to this. I didn't really mean "Serious" muscle mass :P Just the way I phrased it. I do understand that our bodies are different from men when it comes to building muscle.

Thanks everyone for your advice and your own personal experieces. This really has helped

I would say that if you shed the weight exceptionally quickly it was most likely water. Any time I stop or drastically reduce exercising I instantly shed 2-4 lbs. And when I start exercising more it comes back, so if i am combining exercise and diet I often "dont lose" for several weeks because I am gaining water at about the same rate I am losing fat.

Some thoughts -

I wouldn't put much weight into other people's experiences. I'm not saying anyone here is wrong or lying but that people draw poor conclusions based on the data they have more often than not.

Definately start weight training. Tell your trainer you want a 3x a week full body routine based on compound exercises and that if it takes more than 40 minutes (not accounting for warm up or any stretching or cardio after) that he needs to come up with something different.

I wouldn't be so sure about your BMR. Formulas are just estimates. Short of getting hooked up to some very expensive lab equipment, the only way to know for sure is to carefully track for a month or so and if you're maintaining at a certain intake - you're at maintinence calories. Funny thing about those formulas ... the more you're an outlier in height and weight the more they tend to be off.

Finally - if you create too large of a deficit your body doesn't go into starvation mode or stop burning fat. What it boils down to is that the body can only slow down the metabolism so much. Even in the Minnesota starvation study BMR only went down 5-10% after factoring in the loss body mass. Ultimately - in my opinion - it comes down to how you feel. Do you feel over taxed, over worked, and over stressed? If so it might be time to take a break from dieting and/or exercising. If you feel ok - I wouldn't worry about it as long as the bulk of your calories are coming from a mixed diet.