What am I doing wrong?

If you open up your diary, you can get more specific advice regarding your nutrition.

If its just one week I wouldn't even worry about it :] Could be from a variety of reasons. Most likely water weight masking your fat loss. Might see a big drop next week!

Switch up the exercise - cardio is awesome for burning calories as well as other health benefits, but if you only do cardio (and the same cardio workout) every day your body starts to adapt and basically plateau. Add in some strength excercises. Core is always good, but if you have access to a gym there are simple chest, arm, back, and leg workouts you can do as well. If you're constantly doing something a little bit different every day your body won't be able to adapt. That should kick start your weight loss again!

make sure you're not eating junk that can have a lot of calories without you realising. (some foods even at small quantities can be ruining your diet)

and don't worry... keep up the good lifestyle... and it will eventually work!

1st week - lost 6lb
2nd week - lost 3
3rd week - lost 0
4th week - lost 2

This is how it was for me. Stayed under calories and exercised the whole time. It will all work out in time.

1. don't stress over not losing weight every week. losing weight is not fluid and sometimes the body rebels and needs time to adjust to changes you have made. likewise, sometimes you need to adjust so everything doesn't stay the same.

2. exercising every day is not necessary...and perhaps one reason your body is rebelling is because you aren't giving it time to recover. it may be coincidence or it may be a sign that your body does need 2-3 days of rest each week....but you lost weight when you gave your body rest and you didn't lose weight when you exercised every day.

Not to be in your busines but maybe your cycle is close? It could be water as well, Jst keep at it, The scale is not you friend.

I'd bet it's water weight from your increase in intensity/time of cardio workouts. When I first started, I also started working out and it made my weight loss stall for a week or two but then BAM, I lost 4 pounds. Keep doing what you're doing. Your body does need the carbs, especiallly as you're so active. If you're not already tracking sodium, add it to your food diary as that'll help you keep an eye on water weight fluctuations too. Also, keep time-of-the-month (aka TOM) in mind as that can wreak havoc on the scale. Make sure you're drinking plenty of water too. It can help to keep yourself constantly hydrated so the body flushes out the excess easier.

Definitely start taking measurements and/or keep an eye on how your clothes are fitting. I've been slow to lose pounds the last month or two but my clothes are fitting way better than they were.

One week is no big deal. Even 3 weeks is no big deal. Keep on keeping on.

Don't stress about one week!! You will be okay. We all have those. If you stress about it too much then you will start telling yourself-it is not worth it. So just keep on track. Start taking measurements. I haven't lost weight since Feb, However, my clothing size has gone down and my arms are pretty amazing-haha. I have gained so much muscle I haven't taken off any weight at all. So I have let loose of the strength training and am focusing on cardio the next few weeks. Unfortunately it isn't by choice, I am just doing something that doesn't allow me to do any strength training for a little while. So I am focusing on cardio to hopefully start seeing some results on the scale. Though I know some of my muscle will be lost in the process I will get it back as soon as I am better!!!!

I looked at the last week of your diary and a few ideas (esp in light of your comment that you feel so hungry)...

1. try to get your carbs under 150 a day. replace them with more lean protein and healthy fats. both help fill you up. and, as for carbs, try to get your carbs from more natural sources than from processed foods. this will help you with sodium (which doesn't help weight loss), among other things. additionally, carbs with a lower glycemic index value help you feel fuller longer because they don't cause an insulin spike (which is what creates feelings of hunger and cravings).

2. try to cut out the soda. you are wasting a ton of calories on soda a lot of days. no sense doing that. if possible, I'd avoid soda completely (inasmuch as research shows that diet sodas create cravings for sugars)...but if you can avoid the cravings, at least diet soda comes without calories. I gave up soda in April and haven't missed it one bit (after the first few days).

3. I am a 40 year guy with a larger frame. On most days, I don't have a problem with eating fewer than 1300 net calories because I focus on eating lean proteins, healthy fats, and carbs with a lower glycemic index value. pick the right foods and you will also be fine.

4. as far as eating back your exercise calories....part of that depends on how you are figuring out your exercise calories. if you are using MFP estimates, then understand that those are largely overstated by as much as double what you actually burn so if you're using MFP estimates, then eat back at most 50% of that estimate.

I'm working on the soda. When I started MFP I was trying to fit in a 12oz soda a day. Since then I've started buying the smaller 7.5 oz to kill the craving and trying not to drink it everyday. But you're right, I'm wasting calories I could be eating instead.

I think you're going about this in the right way. Just as I mentioned earlier about not adding too much exercise too quickly...I think its helpful to wean yourself off of something like soda. Continue doing so, but here are some things that will hopefully provide motivation to cut out calories from your drinks. just imagine what you could do with those calories you're currently consuming from soda:

1. eat a bowl of raspberries, blueberries, strawberries or blackberries. berries have a low glycemic index value so they won't cause an insulin spike. raspberries come packed with 8 grams of fiber per cup...which will help you stay satiated until your next meal. good luck keeping up with that, mr. soda can.

2. get a tasty protein powder and mix it with water. there are some good protein mixes that come with 20 or more grams of protein and few carbs/fat. if you're going to drink your calories, may as well drink something with a lot of protein to help you stay full longer.

3. hello apple or pear. both great options.

4. just think about how many nutrient rich, filling veggies you could eat. LOTS.

5. a can of coke or a can of tuna? one provides nothing useful, the other provides a lot of goodness.

I could go on...