Losing weight is a chemical/hormonal process. Don't think of the calories burned while working out as necessarily the most important measure of a workout's value. It's the 23 hours after and leading up to the next workout where your body really go to work.

Your body is the same design as early man. Back then your body never knew when the next meal was coming so it held onto fat at pretty much all costs. Muscles produces more energy than fat when burned so your body mixes fat and muscle to sustain your endurance energy needs. The same concept is true of your glycogen levels (or shorter bust energy). If you needed to travel miles to find food your body would hold back most of your glycogen reserve just in case you had to run away from a saber-tooth tiger. When you eat after a workout your body's first priority is to refill that glycogen tank (just in case you have to run for your life again). If you don't adequatly burn glycogen during a workout then the leftover calories you eat will simple be converted to fat for storage, no matter how healthy those calories were. Everything your body does, it does in the name of self preservation.

If you'd like to read more on this one website I'm fond of is Life Spotlight. Although most any fitness or health website or magazine will have similar articles.