There are 2 types of carbohydrates. Simple sugars and complex carbohydrates (see the tables below for example foods for both). There is a place for both in your diet but, ideally, the majority of your diet will consist of slow-release, unrefined, complex carbohydrates that are high in vitamins, minerals and fiber. You may hear these foods being referred to as having a 'Low Glycemic index'. Once eaten, your body will turn these types of carbohydrates into energy gradually. Why is this desirable? For Those Wanting To Build Muscle Fast Firstl, it means that your energy levels are kept stable and consistent throughout the day. This is because your Insulin levels will remain stable. Insulin is a hormone that is released into your body to regulate your sugar levels. How much Insulin released depends on how high your sugar levels are. Taking in fast acting, simple sugars and even complex carbs (some complex carbs have a high glycemic index) will spike your insulin levels because the sugar from these carbs will be released quickly into your bloodstream. This results in an energy crash because what goes up must come down! Your spike in sugar levels will just as quickly end in a fast, downwards crash thanks to insulin. Secondly, and perhaps more importantly, insulin loves to shuttle excess carbs into your fat cells. If you cause your insulin to spike often, you are more likely to store fat which is obviously the opposite of anyone's goals. Even though fat gain is inevitable during a muscle building phase, we want to limit this as much as possible. The only time that fast-release, simple sugars are more beneficial than complex carbs for muscle building is post-workout. When your body is screaming for it's energy stores to be replenished. I'd recommend 50 grams of fast-acting, simple sugars with a whey protein shake to replenish your muscle's energy stores as quickly as possible. This will switch your body from a catabolic (muscle breakdown) state into an anabolic (muscle building) state. For those wanting to lose weight fast\/burn fat All of the above applies and is even more important when you're trying to burn fat. The only difference is that I would forego the post-workout simple sugars to keep your body needing to burn fat for energy. Having only a Whey protein shake would be more desirable to maintain muscle mass. Some people may also need to reduce the ratio of carbs eaten in their total daily calorie intake. This will depend on how carbs effect you individually. A good rule of thumb is to start off with the same ratio of carbs that you would use to build muscle. If you are not losing weight, (1-2lbs a week or 1% body fat a week) then knock off 25 grams weekly until you start burning fat. However, I personally wouldn't go below 50-75 grams of carbohydrates a day. Even if you get that low, it shouldn't be for more than 4-6 weeks. Examples of Slow-Digesting, Unrefined Complex Carbohydrates Wholegrain Bread Wholewheat Pasta Brown Rice Sweet Potato Porridge Oats Vegetables Beans Peas + Lentils Examples of Simple Sugars Fruits Sugar Honey Biscuits Sweets Fizzy Drinks\/Juice Milk Bare in mind that some simple sugars have a slower rate of release like milk and most fruits. Similarly, some complex carbohydrates will have a fast release such as jacket potatoes, instant rice etc so the issue of carbohydrates isn't as black and white as saying ''stick to complex carbs and cut out all simple sugars''. Also, the reason that complex carbs like white bread and white pasta are generally not recommended isn't because they release a lot faster (contrary to popular belief) than their brown counterparts, but because they are stripped of all of their vitamins, minerals and contain less fiber. They release at more or less the same speeds (a little faster due to the lack of fiber) so if you MUST eat white bread, white pasta etc you MUST also make sure that you are taking a good multivitamin supplement that gives you higher quantities of vitamins and minerals (in the correct ratios). You should still stick to unrefined food wherever possible.