Hmm... not sure, but it's an interesting question. The Glycemic Index per se is not the only thing that'll determine if one will lose fat or not... i.e. If you eat too many carbs, even if they're super low GI carbs, you'll still gain fat. That said, I think I understand what you're asking... what GI should I aim to equal or go below with my carbs while dieting to lose fat? Is that right? Well, my guess would be around < or = to 50, but if anybody knows any better, please do correct me. Also, give some examples of carbs that meet these standards.