Answer:
Calories are a measurement of energy and we are supposed to have a certain number of them a day so we do not gain weight when not wanting to. But if you eat a lot fewer calories then you are supposed to, then you will destroy your body and tons of bad things could happen. However, if you wish to lose some of those extra pounds, then you need to exercise and eat healthy because diet is half or even more then half of your weight and what is happening to it. For portion size, it is how much of each food product you are to consume. Everyone needs a certain grams of fat, carbs, protein and others. So, don't eat too many, especially if they are unhealthy ones, but don't eat to few, you can get very sick.
True, it is not safe to do that
The first drug people tend to abuse is tobacco. I hope this helps! :)
