I've read various websites that talk about gluten-free baking or low glycemic index foods but how does these things differ from low carb diets?
The simple answer to gluten is that gluten comes from wheat. It's one source of carbs out of many. It's in important part of baking, but a significant number of people have celiac disease or some other form of gluten sensitivity. As a result they need a gluten free diet.
The paleo diet and diets similar to that avoid all grains. They associate a number of bad things with grains and claim that our paleolithic ancestors didn't eat like that. Since no-one is still alive from that era, this is of course an educated guess.
This much we do know:
- The organ most affected by carbs is the pancreas
- The pancreas secretes insulin when the blood sugar gets high, which plays a role in regulating blood sugar and trapping excess sugar as fat
- The pancreas also secretes glucagon when the blood sugar gets low, which plays a role in regulating blood sugar and converting fat to blood sugar.
- Foods with a high glycemic impact will cause the pancreas to secrete more insulin than those with a low glycemic impact
For people who are very sensitive to insulin levels due to being insulin resistant or diabetic, you absolutely have to avoid the high glycemic impact foods. However, it doesn't hurt people without those ailments to avoid high glycemic impact foods.
The Paleo diet claims that a more natural source of carbs would be your whole vegetables--particularly the ones that you do not have to dig to get (i.e. not tubers like potatoes). The general concept that the more processed a food becomes the less healthy is fairly sound. In short the body doesn't have to work as hard to break it down and incorporate it, and the processing tends to remove the most useful elements from the food (vitamins and minerals).
While I personally think that the Paleo diet takes certain aspects too far, such as removing all grains and legumes from your diet, in general there's enough to its principles to learn from.