Yes have done, BUT you need to restrict calories as well though as low GI eating on its own will not necessary result in weight loss - lots of low GI foods very calorific.
Also I think its a bit outdated now as it has been shown that some "high GI" food actually contains very little carbohydrate example is watermelon (ie it has a low Glycemic load), so eating it wouldn't affect blood sugar that much.
I have lost quite a bit of weight recently and I have include an element of GL in my method. Basically I aimed to create a calorie deficit by eating a bit less and exercising a bit more. I started off quite strictly but when I saw my son eating the lemon off his fish I realised I had to do something more sustainable for all of us. My main problem I think was snacking actually caused by my efforts to eat less. Another problem was simply putting too much on my plate at dinner. So basically I start the day with two pieces of toast made from bread with as much rye, seeds etc as I can find, and spread thinly with any kind of nut butter. No actual butter. I try to eat more protein in all my meals. I have a light lunch. By dinner time I aim to have eaten no more than 600 cals. And I bought a 10" dinner plate. This is 'mum's plate' at dinner. Thought the small plate thing was daft but it does make a difference. I did a bit of swimming for a bit but mostly I try and walk more. Motivation: two suitcases. One with clothes I was too big for. The other was empty. As I lost weight I took clothes out of the 'smaller sizes' suitcase and put them back in the wardrobe, and started filling the empty suitcase with clothes that are too big for me. I don't have scales in the house so this is my way of understanding the weight loss is real. I estimate I have lost more than 2 stone since January and am nearly back down to what I was before I had the kids, which is 20 years ago.
Missed a crucial bit. It is important not to let yourself get hungry. That's when you'd eat a dead dog fried in batter. Hence the toast and nut butter. White bread with jam would make my blood sugar whizz up and crash and I would be starving by 11 am. (Usual caveat, I have absolutely no medical quals).