Originally Posted by twinieten
Aren't they one in the same? Can you explain what you mean?
Fat is stored energy. You eat more calories than you burn over a period of time (lets say a week) and you will have stored a net amount of fat over this period of time. This is fat gain. Conversely the opposite causes fat loss.
Your weight is how much you weigh which is affected by everything inside your body including muscle, muscle, glyocgen, bones, water, fat, digesting food, waste products, etc.
If you go on a low carb diet, your water weight will immediately be reduced as your muscle glycogen stores are reduced. For someone my size that might mean 8 lbs. However if I reintroduce carbs muscle gylcogen storage will increase and my weight will rebound.
Did I lose 8 lbs of fat and regain 8 lbs of fat? No.
Fat loss or gain is an equation of energy. Energy is measured in calories. Unfortunately there is no inexpensive way to measure fat loss so people rely on weight to measure progress which is a bad idea because the scale can flucuate a lot especially in women. Pictures and measurements are far better indicators of progress.
Hope this helps.