We can do that by comparing our current TDEE with TDEE at the start of using 5:2. You can find current TDEE at the progress tracker. For the TDEE at start: enter a new ‘weigh-in data’ using your weight at the start of 5:2. Check the tracker home and you see the TDEE at start of 5:2. Write it down and delete the new data.
Take the difference between TDEE at start and current TDEE (for me that’s 200), divide it by 1100 and you get the weekly weight gain in kg. It is the weight gain that you would get in a week if you would today have been eating according to you diet at the start of 5:2. So, it is the weight gain that you have prevented by your current successful maintenance strategy (for me that’s 0.18 kg.). In case your weight at start of 5:2 was not stable, but was rising: add the weekly weight gain that you had at the start.
Total weight gain prevented is number of weeks on maintenance in the Xmas club times the weekly weight gain prevented. (for me: 4*180=720 grams)
Make sure you update your total weight gain prevented each week by adding another 'weekly weight gain prevented' to your total!
Just remember, if our brains look like those of mice, 5:2 is supposed to make us smarter as well, you I am sure you will all be able to make these caculations