I'm starting a low carb diet tomorrow and have been reading up on it lately as I want to do it right! The plan is to have a carb serving for breakfast (porridge) and for the rest of the day get carbs from vegetables only.
Do I treat a portion of quinoa as a carb or a protein?
Carb. Try it for breakfast if you get fed up with porridge.
Get the non breakfast carbs from vegetables, berries and whole fruit.
A low carb diet involves understanding the carb content of everything you eat, and putting a limit on your daily intake. Quinoa has 8.something carbs per 1/4 cup - cooked (from a quick Google), so it's pretty carb dense, really. There are a lot of low carb diets out there, and I favour Atkins (though of course it's not the only way), but something to think about is finding the daily carb level at which you lose weight (this is what Atkins is all about, really).
Some people can lose weight at 100g carbs or more per day, others (like me) have to stay under 40g. Atkins starts you off (for the first 2 weeks) at 20g carbs per day, and those carbs mostly come from green leafy vegetables. After that, you gradually introduce more carbs into your diet until you find the level at which you still continue to lose. Information is power!
Once you know how many carbs you can happily consume and still continue to lose weight, then you can play around with how you get those carbs. There's more to it than that, really, (stuff like the nutritional benefit of what you're eating, and its contribution to insulin production etc.) and my advice would be to research existing low carb diets and then make a choice.
Understanding how these diets work is the key to success, in my opinion. There is far more to it than just reducing overall carb level. Porridge for breakfast would be a non-starter for me (it would induce cravings, and make me sluggish), but everyone's different. I dunno if I'm allowed to post links to helpful sites here or not, so for now, I won't, but I've been eating the low carb way (with one big fall off the wagon, am back on it now) since 2005, so feel free to drop me an IM for pointers