Smoothies, Oatmeal, & 'Macros' Questions

Hey so I'm, obviously, trying to lose weight and recently I've been looking at a LOT of fitblrs and health blogs and these forums and I have a few questions.

1) Smoothies. I hear they're pretty amazing. What kind of smoothie is the best in terms of having the most nutrients and low cal? What ingredients should I put in it? I can't eat most yogurt, but soy milk would be ok right?

2) Oatmeal? So many health blogs I go to rave about it but I've never seen why. Whaaaat is so good about oatmeal?

3) A lot of people say low carb is the best but then other people say low fat is. I'm not trying to adhere to any 'low-anything' diet, but just wondering which is worse to have too much of, carbs or fat?

Thank you for any answers or help. :)

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