In the bodybuilding environment there are many new myths, new kinds of behaviour, supplementation and training which are copied without any second thought. Here is the review of the most popular statements which are not scientifically justified.
Myth 1: “carbohydrates will make you fat”
Yes, carbohydrates cause the insulin burst, and insulin contributes to removing glucose from blood and it can cause gathering too much energy, e.g. in a form of subcutaneous fat, or that around inner organs. And here is an important information, you can lose weight when eating 3 meals a day at McDonald's (in a way not to exceed the daily demand for calories), you can also lose weight eating pizza and cakes, in other words, eat very badly. Of course, it makes no health sense – such diet may decrease body weight (I have to underline it – not reduce body fat), and destroy the body from inside! I have explained many people that they are wrong when they decide to use drastic reduction diets, which lack protein, fat, vitamins or other nutrients. I am not completely certain if they are convinced – because “they have noticed the results on the scale”! This matter concerns e.g. an absurd diet prepared by a “specialist” (which was described here: The antidiet from a dietitian).
That diet was following:
energy: 1300 kcal
digestive carbohydrates: 230g
Obviously, such diet will contribute to losing weight. If you have read the previous articles, you will understand that the insufficiency of healthy fats is the easiest way towards hormonal problems (testosterone is produced out of cholesterol). It was shown in many studies that starting low-fat highly-fibre diet decreases the level of testosterone (total, free) by even 12% . Additionally, in the cited experiment, the scientists noticed the decrease of androstenolone, DHEA. The decrease of testosterone contributes to faster loss of muscle mass, strength, and it disturbs recovery.
Fats play an important role, because: “cholesterol is the starting compound (precursor) of bile acids, steroid hormones (corticosterois, cortisol), adrenal cortex hormones (glucocorticoid and mineralocorticoids), male hormones (androgens), aldosterone, testosterone, female hormones (estrogens) estrone, estradiol, gestagens -among others, progesterone made in the body”. 
In addition, we know that cutting on calories too much blocks metabolism and, as a consequence, “burning” body fat. After few weeks of destroying your body, you start hitting a wall and there occur questions, like: “why? It's been so good so far!?”
Finally, too small amount of proteins influences metabolism most. It slows down and the loss of muscle mass is stronger (during reduction you should provide even 2.2 – 2.5 g of proteins per 1 kg of body mass! 50 g is appropriate for an inactive person lying in bed). After finishing such diet you will remain without muscles, with disturbed metabolism and in much worse sports form than before using it!
To sum up: there's no magic here. Whether you build mass, or lose body fat depends on the energetic balance. If you supply too much carbohydrates, then in adverse hormonal-training conditions, some part of it will definitely be stored in a form of subcutaneous fat. However, you should not beware of carbohydrates. Fattening is a slow process that you can regulate by observing yourself in the mirror and measuring the fat fold. Carbohydrates don't cause gaining weight, provided they are not in excessive amount. Because of health reasons, it's good to limit saccharose in diet (table sugar), as well as glucose-fructose syrup (commonly used in tens of food products), other forms of sugar (cane sugar, brown sugar, honey), glucose, fructose, dextrose, gainers or carbohydrate conditions (carbo, vitargo, maltodectrins, etc.). A sportsperson should base on noodles, buckwheat groats, millet groats, brown rice and wholemeal bread. Too much food is fattening, not one “magic” component of diet.