Does sugar alone cause weight gain or is it because sugar causes you to eat more? thanks! :)

Both: ↑es Insulin &: are converted to triglyceride fats for storage: http://goo.gl/H7mItd. Insulin stimulates uptake by cells, often resulting in a drop within ~2 hours; tending to result in recurrence of hunger. This is an issue with all carbs (sugars, both simple & all complex) yet is a greater issue with simple sugars. All carbs absorbed only as 1 or 2 sugar molecules. More complex carbs take ↑ time for absorption.

Both: Eating simple sugars lead to high insulin release leading to increased fat synthesis and increased appetite especially for sweet and fatty meals