One of the downsides to low glycemic eating, if you consider it a downside, is the need to eat often. Your blood sugar level doesn't have a lot of wiggle room. So, it becomes necessary to provide a steady supply of LG food. Even so, you lose some weight.
You do, however, have to think ahead and carry snacks. If I don't do that, I start to get a hunger headache. You may experience the same.