It may well be that you aren't eating enough and your body is retaining what it's got incase it 'doesn't get more'. 1500 seems kind low for a guy who's exercising. Is the running replacing some other type or exercise?
Also, I saw a documentary once (not that this makes it true...) on a group of out of shape (only slightly overweight, not obese) folks that went from sedentary to a marathon- with physician and scientists testing, charting, overseeing, gathering data... And all got healthier- better heart rates, blood pressures, lab reports, ... but no one lost weight except the one gal who also added weight training to her fitness regiment. Food for thought-

Here are my two cents, I am answering because I saw your post under the low carb heading so I would suggest you go over to Mark's Daily apple web site and read about your conditions and how low carb can help you.

My own story is that I cycled for a month and could not lose weight then when I went low cal then primal my weight came of and has stay off. I am at 216 right now and I was at 250 4 years ago.

You could try eating back your extra expended calories for a week and see if it changes your weight loss. Take measurements as well though, as you may be losing fat and gaining muscle (muscle weighs more than fat).

I started running early this year. Did my first 5K (on the treadmill) in March and that got me serious about running as my main form of exercise. Sometime in April I hit the mid 180's and kinda got stuck there. That freaked me out because I had hit a plateau last fall and didn't lose for 3 month. The only way out of it was when I doubled my workouts. Thought I'd better hit it hard again so I started running more and more. I would be on the treadmill 2-3 hours a day 5-6 days a week. I also teach an aerobics class 3x a week. I stayed yo-yo'ing the same couple of pounds for 6 months.

Last weekend someone sent me an article on chronic cardio and it was an eye opener. I went to the Dr Tuesday to see if he could help me target a healthy, realistic goal weight (I was aiming 130 and he said 150 till he realized fitness was my goal and he revised that to 160), and when he heard how much I was working out, he told me to cut that to an hour of running every other day.

I haven't cut back quite that far, I'm running an hr every other day, but I've added strength training and I walk 4 miles on my strength days and I've already dropped several pounds this week. A big drop the day he gave me a water pill, but I'm still dropping daily several days later.

I joked to someone that it's like my body is breathing a huge sigh of relief. LOL

Anyways, I don't know if chronic cardio is your issue...are you running daily? I don't know if you've been doing it long enough that it's chronic cardio, but at the very least maybe you can avoid getting to that point.

I'd say add strength if you aren't already.

4 lbs per week is alot! if you kept losing that much month after month you'd shrivle and die. The body is smarter than that it wants to live. Relax and give the scale a break.