since your calories are coming from protein (with the atkin diet) and not carbs, you should actually be sustained for a very long time on one bar which has 18 grams of protein.. it is very filling.. you won't simply feel a satisfaction for an hr and then be hungry later.. it has a sustained release rather than a peak and a decline...
that is in fact why I have recommended it with the shakes.. although again protein overload in and of itself isn't without its problems. (which are too expansive for me to get into at 2:30 am)
I simply recommend the atkin type diet for Ramadan, it doesn't have to be a bar, and a shake, but you can try eggs or beans, dates are also excellent.
and Allah swt knows best..