​Workouts - fasted or fed? Which is best?
Fasted:
*a noticeable improvement in insulin sensitivity. 
Poor insulin sensitivity happens when we eat too often. When the body is in a fasting state, it releases insulin less regularly, thus making us less sensitive to insulin and heightening our opportunity to lose fat.
*an increase in human growth hormone (HGH). In tandem with proper sleep and regular exercise, growth hormones help with building new muscle tissue, burning fat and improving bone quality and physical functions.
*help ensure nutrients are distributed efficiently and minimize accumulation of body fat.
* increases the amount of protein tissues burned for energy, sometimes exceeding 10 percent of the calories burned — double that if you exercised in a fed state.
* Boost muscle glycogen storage efficiency. Occasionally fasting helps the body adapt to using available fuel in the body. Then when you actually perform a workout in a fed state, your performance will be much better.
Pre-fuelled:
*When working out in a pre-fuelled state, you can perform higher-intensity exercises for longer due to the body’s need for energy, resulting in better muscle gains. The more carbohydrates you burn while exercising, the more fat you burn post-workout and vice-versa. The body needs energy to work, and eating before exercise increases excess post-exercise oxygen consumption (EPOC).
*Eating before exercise also results in consumption of fewer calories later in the day. This is probably due to the efficiency of the body in using the absorbed nutrients from the carbohydrates. Fat burning is also negligibly lower compared to those who fast before working out. Research has shown that people who eat complex carbohydrates before a morning workout session have much less total caloric intake for the whole day.
*Bottom line, there’s no right or wrong here.
Different people and their bodies have different needs. 
So exercising, whether in a fasted or a fed state, all depends on how your body responds and which feels more comfortable.
For example, I enjoy fasted runs, swims and cycle rides at a steady state but I wouldn't attempt HiiT in a fasted state personally - my body likes to be fed and settled before I attempt higher intensity workouts. That's just me and what I've learnt about my own body and what is it prepared to do for me during a workout.
There are many other factors that contribute towards how you feel - you know how your body works better than anyone else so listen to it and experiment until you find what works best for you.

Your head weighs around 5KG (much heavier than you imagine)
Put a 5KG weight into your outstretched arm for a while and then have a think about how important it is to have the correct posture when you run, when you walk, when you exercise and when you sit at a desk.