Today a friend shared with me his method of losing weight, "fasted cardio".

Theory: Blood sugar levels are low when you are in a fasted state (after going all night without eating) which targets more fat burning.

Question: Exercising on an empty stomach (usually morning after waking up), will it lead to accelerated weight loss?

So i did a research, typing "exercise on an empty stomach". So this is what i found.

Studies shown that fat burning does not start until you are 20 minutes into you cardio workout. Meaning the 1st 20 minutes of cardio you do is "warming up", then your body starts metabolizing fats. If you don't have a good source of fuel to sustain you, you would get tired more easily leading to a shorter workout session and burning lesser calories. Critics also say you may burn muscle if you don't have the necessary fuel for you workouts.

Disadvantages of exercising on empty stomach…
Likely to get a shorter and less effective workout, due to:
Unnecessary fatigue
Lethargy
Dizziness
Dehydration
As a result, you burn less calories because you can’t keep going as long as you should have been able to.
It’s also the thought that exercising on an empty stomach, you can eat more after the workout.

Benefits of eating before you workout:
Helps energise your workout, boost recovery and strength gains
Prevents low blood sugars, which can make you feel dizzy, nauseous, and lethargic
You can exercise more intensely and sustain longer
Your workout will be more enjoyable overall (since you are not thinking about eating the whole time)
Can boost your recovery time

Exercising for weight loss: Plan of Action
Don’t worry about the time of day – just go with what fits your schedule
Do cardio training three days each week
Do strength training three days each week
Train in hard, short bursts
Eat regular meals and snacks containing carbs, protein, fruit and veggies
If exercising in the morning, have a healthy breakfast/light snack (100-200 calories)

The bottom line is, my friend, it is up to you and the type of workout you are doing. Some people are fine doing cardio without fuel in the morning. Other people workout so early, they may not have time to eat anything. The best thing to do is, do what works for you, every single person is different. Don't go hungry just because you think you are burning more fats. After all, if you cut the workout session short/ lower the intensity because of low enegy, how much fats are you burning anyway?

And if you do eat before a workout, make sure you give your body time to digest. The larger the meal, the longer time you will need. If you choose a light snack (100-200 calories) you can probably exerie after about 30-60 minutes.

Resources:
http://exercise.about.com/od/weightloss/f/emptystomach.htm
http://www.dietriffic.com/2008/11/19/exercise-on-empty-stomach/