Protein and weight bearing exercise is the key to retaining muscle, not carbs. Most low carbers increase proteins and or fats rather than carbs once they reach target weight. BMI has some serious flaws as a sole judge. If you still have belly fat/high body fat how confident are you that you are the right weight now? How does height to waist stack up?
There is no such thing as carbs too low. Whilst almost all of us choose to incorporate some carbs of some type in varying amounts we can survive just fine without them. Any standard nhs eatwell based course, as yours is, will advocate nearly 40% starchy carbs and then there’s any more that come from fruit veg beans and pulses so in all likelihood it’s well over 50% in total. Conversely the nhs in some areas also funds the low carb program which advocates considerably less than eatwell as do various other nhs organisations and practice. Which boils down to; eat what works for you to maintain you blood glucose and weight and sanity rather than an arbitrary number that your body doesn’t recognise
