Without turning this explanation into a physiology lesson, I'm going to keep keep it as simple as possible.
Carbs eaten in excess can make you fat
Carbohydrates are our body's preferred source of fuel and they are stored as glycogen in our muscle tissue and liver. There are simple carbs, such as candy, fruit and soda- which are fast digesting (low in fiber) and there are complex carbs such as oatmeal, sweet potatoes and brown rice- which digest more slowly because they contain more fiber than simple carbohydrates.

How can carbohydrates make you fat?
When you eat a candy bar, it digests rapidly and breaks down into your blood stream causing your blood sugar and the hormone insulin to rise. Now say you are about to run a marathon, that candy bar will no doubt be used to fuel your intense run. On the other hand, say you eat the candy bar at 10pm right before you head to bed for the next 8 hours. Those calories and grams of sugar will most likely be stored as body fat because they have nowhere to go (unless you have a super fast metabolism). Not to mention, you will probably have a wicked sugar rush.

When you are overweight, the last thing you want to do is provide your body with too much energy in the form of excess carbs. You want to create a caloric deficit to encourage your body to give up stored body fat and increase the amount of physical activity you peform in order to speed up your metabolism. The reason that low carb, high protein diets work so well is because you are eliminating that buffer (carbs) that prevents the use of stored body fat for fuel- the body chooses carbs every single time. Once the carbs are lowered or cut out entrirely, the body has no choice but to use stored body fat for fuel. Also the body has the ability to convert protein to a usable, albeit last resort form of energy to fuel the brain and other activities.

There are some disadvantages to lowering carbs, so you will have to experiment (safely) to see what works best for you:
- When you lower carbs, your cognitive function suffers quite a bit. Some people are more irritable, lethargic and have a hard time remember things.
- Without the constant intake of complex carbs, you may get constipated within a few days of consistent low carb eating. Make sure you supplement with Metamucil to help keep things moving!
- Stay hydrated! Protein contains nitrogen, which in large amounts can be toxic to the kidneys and liver. It's vital that your intake of water increases as carbs decrease.
- Supplement with extra Vitamins B and C. When your body is not receiving a diverse amount of nutrients from fruits especially, you may need to take in more of these vitamins. Always check with your doctor.