New and have some questions, please help

So I've been using this website and have been on my diet for 4 weeks now. My first weigh in was at 169 lbs (I weighed myself right after lunch). Now, I weigh in every Friday morning (before breakfast). 

I am 5'5" female.

I have already lost 10 lbs. Which is... you know, great. But I'm really not seeing the loss, nor has anyone commented on it. I'd think 10lbs would be relatively noticeable since 169 lbs to 159 lbs seems like a lot to me.

I'm concerned about one thing, and could really use some information that makes sense. When I started, I found myself eating 800-900 calories a day. I lost 4 lbs in the first week. After reading the forums, I realized this is far too little. So starting week two and ever since, I've been averaging around 1200.

My BMR is 1800.

I'm concerned that I'm losing muscle rather than fat. This "starvation mode" thing has me frightened that the 10lbs I've lost is all muscle, and that's why no one has noticed anything.

I'm really trying to get my endurance up to exercise more often. I am a smoker, and working on the motivation to quit. So exercise is difficult.

So my question is this.... What's the difference between eating 1200 calories a day with little/no exercise... Versus eating, say, 1500 and burning 300 with exercise. Either way my body is at an 800 calorie deficit (according to my BMR). How is it any different? Will my body go into starvation mode with each of these senarios? Do you guys think the 10 lbs I've lost is indeed muscle due to starvation mode? Please help. I've lost 10lbs and the fact that I'm not and no one else is seeing it is really weighing on my spirit.

The first initial weight loss is always going to be mostly water (not fat or muscle), especially if you lose it quickly. That is not necessarily a bad thing but it can be frustrating for many people because after the quick water weight loss the rate at which the scale moves down slows drastically. As for muscle loss vs fat loss, you will lose some of both at the same time. To maximize fat loss and minimize the loss of lean body mass (ie: muscle), it is important to fuel your body with an adequate balance of calories coming from carbohydrates, proteins, and fats.

Whether or not 1200 cals is adequate for you personally to maintain a healthy nutritional intake to promote sustained fat loss is difficult to determine without metabolic testing, but it is certainly unlikely. Definately do not go below that amount however, as you will not meet your daily basic nutritional requirements and this highly restrictive intake will be nearly impossible to maintain long term.

Log your food into cc to assess if you are meeting your personal nutr needs and weigh yourself periodically to trend your weight changes. You should see a loss of no more than 1-2# per week from this point on.

Actual body fat loss per pound is equal to a 3500 cal deficit. So you will need to burn (over a period of time) 3500 more calories than your body requires to maintain your current weight. The most logical and sustainable way to achieve this is through a combination of moderate calorie restriction and increased exercise.

Thank you for the tips. I feel slightly releived that my current weight loss is most likely water weight and NOT muscle.

(with a BMR of 1800) The biggest confusion for me still is the difference between an 800 calorie deficit from simply not eating those calories, and an 800 calorie deficit via exercise. In one scenario I'm eating about 1000 calories a day (with no exercise) and in the other I'm eating like 1400 and burning 400. Both give me an 800 calorie deficit. Will both cause starvation mode?

Rather than having big differences in your food intake (which makes it tough to get into a good healthy eating pattern) try to aim for a happy medium i.e. 1400-ish cals a day, every day.   Some days you'll have a deficit of 800, others 400... but it'll average out over a week.   1000 cal intake is not a good idea if it's happening regularly.... it will make weight-loss tougher, you'll lack energy and you could end up making poor food choices to make up the shortfall.  Aim to be active every day, even on days when you're not formally exercising.   Take a walk every day, for example.  Regular gentle exercise is better for weight-control and good health than sporadic vigorous exercise. 

If you go with 1400 cals and therefore a slightly smaller deficit your metabolism will stay livelier.  If you eat regularly, ditto.   Every couple of weeks have a day where you consume the full 2000 you need to maintain your weight.  Best of luck

gi-jane gives such good advice!  i have a bmr of 1800 too, and i try to do what gi-jane says - i have a calorie target of 1450, but don't worry too much about it (i range from about 1250 to 1650).  i have the occasional day where i go completely off the wagon (2000-2500), but because my body isn't completely freaked out by not having enough calories on a regular basis, those high calorie days don't result in immediate weight gain (and the occasional high calorie day reassures my body that all is well, and it doesn't need to conserve).    i lost 35 pounds in about 5 months by using that 1450 target (i don't "exercise", but i'm a NYC-dweller, so i'm active).  in the past, i'd try to stick to a 1200 calorie a day diet, and not only did i not lose as much weight, it was incredibly unpleasant.  1400 is the way to go!

Thanks guys I really appreciate all the tips and advice.