I'd like to remind you to provide context and to give your threads appropriate titles.
Here's the best I can do without context:
خفض وزنه بمعدل 4 باوند أو 11 باوند
(I did not translate "pound" because it is an English unit of measurement. My dictionary suggests رطل إنجليزي but that's hardly helpful since most people wouldn't know what that meant. A pound is equal to approximately 454 grams.)
I'd go with Ayed : pound is رطل for the expression رطل إنجليزى is not really used, though I found it in Al-Mawrid. But Hans Wehr puts an interesting note : the equivalent of the رطل in different Arab countries (maybe this is why we prefer the metric measurements)
As for the translation, I think we can also say :
نقص وزنه حوالى 4 أو 11 رطل
دراستي كانت فرنسية و العربية تعلمتها فقط من القران
I considered حوالي but معدل is more precise, and there can be a big difference between the two - depending on the context. That's why I asked Fatiha to provide more context.
As for رطل, I really don't like that at all. It's not like everyone will expect it to mean "454 grams" (which is the same with رطل إنجليزي, which doesn't help much at all). The fact that the translation is different in different Arab countries makes it even more problematic. To me it definitely means 3 kilograms; to you it may mean something else. For these reasons, I think that leaving it untranslated is the best option - to increase the likelihood of intelligibility.
Of course, we could also say something like رطل (إنجليزي)، الذي يساوي 454 غرام, but either way I think the quantity should be expressed as clearly as possible.