The maths of fat loss is simple when you look at it and you can easily factor in why straying off plan regularly can cause issues.
Say you have 30lb of body fat to lose. This is 105,000 calories stored. This means we need to create a deficit of 105,000 calories for you to drop this amount of fat.
A 140lb woman needs around 1800 calories to maintain weight. A sensible 20% starting deficit allows roughly 300 calories to be taken away, so 1500 calories needed a day.
So we have 300 calories available to drop. We can also burn off a further 300 calories form roughly 30 minutes of cardio. So 600 calories a day deficit from diet and cardio.
This means 105,000 divided by 600 is 175 days needed on a 600 calorie deficit to clear 30lb of fat. To decrease this, we either eat less, or move around more with cardio etc.
If we can increase the deficit via diet, exercise and cardio to 900 a day, this means 116 days or 4 months – which is why we typically sell out 16 week plans – as the average woman has around 30lb of fat to lose when the come to us.
This is just an example, but shows what is needed for comp shape being achieved in this instance (not many women need to drop to 110lb!) but even so, you can do similar maths for a woman dropping 160-170lb to 130-140lb, and a similar path remains.
Make sense? 
And I forget.. this is why if you add 1000-2000 calories regularly into your diet via cheats, you delay your progress as 2000 calories is a WEEK’s worth of diet deficit (at 300 calories diet deficit per day).
2000 calories = add a week extra to your diet.
