Using pulses is a good way of getting protein and making a large portion on fast days. I have been wondering how home cooked pulses compare with tinned ones nutritionally, and not surprisingly home cooked ones contain fewer calories, more protein and less salt (apparently much of the high salt content in canned chickpeas is reduced by thoroughly rinsing but I haven't been able to find data on this). I'm not surprised that the commercial/canned chickpeas weigh more, because the convention is that each tin contains 240g drained weight of chickpeas. Heavier chickpeas have a higher water content, which is a common way for food producers to give us consumers less food for more money. (It's also the reason many processed meats and fish have a high salt content, because the higher the salt the more water the product will hold).
Here is the comparison for one cup home-cooked chickpeas vs canned :-
Since I'm going to all this trouble to improve my diet and lose weight it would be daft to eat less nutritious food – especially on fast days – so I'm going to cook my own pulses from now on.