Yes and no. Your body lives off of energy. We get that energy from food. And water. Food contains vitamins and food gives us energy (as said above). If you take extra vitamins your body will feel more awake because of that extra "boost."
If i saw a video ad that shows a man talking about the diet pill he uses while they show that he is not an actor and doesnt read any type of script. This type of advertising technique is called plain folks - "letter B". plain folks type of advertising is commonly used for food and drug type of products.