I'm going to give an example with numbers. I won't include exercise here to keep it simple.

Let's say we have a person in a metabolic ward with a measured BMR that is currently at 2000 calories per day, before they start the experiment. This person eats exactly 1800 calories per day of a low-fat diet (60% carbs, 15% fat, 25% protein).

He eats his first meal of the day.
600 calories total.
400 is taken up by the fat cells to be used in between the next meal.
200 stays in circulation in the blood stream and/or was used for digestion.

Normally when the circulating available energy becomes a bit low, your insulin will also be lower, allowing energy to exit from your fat cells. BUT if this person has a problem with insulin resistance, the insulin levels will stay high longer after the meal and less energy will be able to exit the fat cells.
If non IR: In 5 hours 400 calories will be released from fat cells.
If IR: In 5 hours only 200 calories might be released from fat cells.

For the same time frame depending on your metabolism you might use less energy from your fat cells. Also, if the person is IR they will become hungry earlier than if they were not insulin resistant.

So when the person reaches the second meal.
If non IR: 0 calories from the previous meal is still stored in the fat cells.
If IR: 200 calories from the previous meal is still stored in the fat cells.

Repeat this for all the meals and you come to this.
If non IR: 0 or -200 calories removed from fat cells. His metabolism could have slowed down to match the available energy (1800 calories). So his actual measured BMR at the end of the day would be 1800. No weight change. If his metabolism did not yet adjusted to the lower available energy, an extra 200 calories will have been taken from the fat cells and a small weight loss occurred.

If IR: 400 calories added to fat cells. His metabolism could have slowed down to match the available energy (1200 calories). So his actual measured BMR at the end of the day would be 1200 and weight was gained. If his metabolism did not yet adjusted to the lower available energy, this person will really be hungry now. In the longer period from super to breakfast of the next day, his insulin will have a chance to be lower. So his fat cells might be able to release an extra 400 calories during this time and there was no weight change.

So as you can see with the same numbers you could lose, maintain or even gain weight on the calorie restricted diet. BUT your calorie intake per say had nothing to do with losing or gaining here. It's only the type of calories and/or the way that your body handles the food molecules that had an effect on gaining or losing.

This scenario would be completely different if the person was eating a zero-carb diet (75% fat, 25% protein), maybe in another post.

Patrick