A startling fact is that carbohydrates are not responsible for making people fat. Don't feel too badly though, you are not only person who was sold on idea that a high protein, low carb diet was only way to lose weight.
Here is a simple way to demonstrate this fact. Think about vegetarians you know, are there any overweight problems among them? The high protein diets rely on a lot of animal fats and proteins, but these vegetarians don't eat them. Startling indeed, isn't it?
Maybe you don't know any vegetarians. They certainly are hard to find, especially in Midwest, where I live.
You may wonder about science involved here. After all, many of those folks promoting low carb diets are medical doctors, aren't they? Being a medical doctor doesn't mean that you don't ever make any mistakes. Besides, same science that supports low carb diet also supports high carb diet. They didn't get it wrong, they just didn't consider whole story.
That might sound like a contradiction, but it isn't. I'm going to explain why in just a moment. Fist, let me give you science on this. You most likely are not a biochemist or a physiologist and neither am I. But I have studied subjects a bit. Don't focus on technical jargon in next paragraph, just try to grasp overall point. You don't need to be a scientist to use common sense and basic reasoning skills. Ready?
Consider this bit of biochemistry. Malonyl -CoA exists in high amounts when there is plenty of metabolic fuel present. Thus, carnitine acyltransferase is inhibited and this in turn prevents acyl-CoA from crossing into cellís mitochondria. Another enzyme is inhibited by presence of NADH and Thiolase is also inhibited by presence of Acetyl-COA. In short, when a lot of glucose is present, fatty acid metabolism is inhibited.
It is last sentence that clues us in here. Basically, a cell will not convert fats into energy if there is glucose present. When cell has carbs and sugar to work on, it will not convert fat to energy, thus fat gets stored.