>Weight loss happens when you burn more calories than you consume. It's not any more complicated than that.

Well, it is somewhat more complicated than that; the devil is in the details of "burn" and "consume" (and, to a small extent, "weight").

What you've said is certainly true as a broad and general statement; this isn't a disagreement, but a point of additional detail. That extra detail is to be careful about numbers "burned" or "consumed" in practice. Because, for example, a treadmill's "calories" readout is just an estimate. A packaged food item's "calories" count is an estimate. You may actually be burning more or less than the machine says when you work out, depending on your body (muscles, heart, etc). You may actually be gaining more or less when you eat the food, depending on your body (digestion efficiency, etc).

And there's also some amount of weight fluctuation for non-calorie reasons - mostly water weight going up and down. This last part is one of the big traps for people just starting a nutrition and/or exercise path, as those fluctuations will initially be bigger than the long-term trend caused by calories.