I'm 5'8, 223lbs. I've lost 5lbs in 4 weeks by eating 2300 calories a day, 3 days a week I do Cardio (exercise bike, walking, snowshoeing), 3 days I do resistance training on my total gym. Never burning more than 400 calories. I do work a job where I'm on my feet MOVING all day, which is why myfitnesspal gives me 2300/day (and that is to lose 1lb/week so they tell me). I usually have 3-400 calories left each day after eating and exercise, so that helps, too.

Your likely eating too little. Sure some people can do that, but I find a slow gradual loss the best without starving your body. I might have only lost 5lbs, but my jeans fit 100% better. 38's now fit perfect where before were almost too tight to wear. Shirts fit better, too. My 7 year old cycling shorts are now showing signs of stretched out, so I need new ones before spring! Less inches on my legs, butt, and waist. Weight is not as important to me as fitting into smaller clothes again!

And it depends what KINDS of foods you eat. DO NOT deny your body of protein, good fat, and fruits and veggies. Take it easy on carbs, or you'll likely never lose much. Cut out ALL soda and most alcohol. By good fat I mean nuts, butter (in moderation), Olive oil... not the fat hanging off a steak, or most vegetable oils. Soy or Whey protein shakes are a good way to supplement your diet.

Also, muscle weighs more than fat. If you had no muscle mass before and started exercising, sometimes you build muscle while burning fat, and your weight doesn't change much. But you SHOULD notice clothes fitting better