Fasted Cardio Math

Why you're over complicating things again

There's always a huge discussion in the fitness world about fasted cardio and whether or not it's better at burning fat. You'll typically hear two points of view. The coaches with degrees in nutrition/exercise science will shout that it doesn't matter when you do the cardio, while those who learned their craft through the bodybuilding world will typically side with fasted cardio. So, does fasted cardio burn more fat?
YES!

Now, since I like to do the math on these things, let's see just how much more fat you will burn with fasted cardio.
We're going to consider two scenarios:

Non fasted cardio, where the person has a blood sugar reading of 100 mg/dL
fasted cardio, where the person has a blood sugar of 70 mg/dL

With fasted cardio, your blood sugar will probably start lower, and there's no food to keep the blood sugar stable (instead the liver does that...and possibly also glycogen from the muscle when the liver runs low). So, with less sugar in the blood to be used for energy, the body will need to offset that difference with energy production from fat. That's the goal, right?

Well, how much sugar is actually in the blood?

I don't think I've ever seen this discussed, so let's do the math.
Taking person 1, with a blood sugar of 100 mg/dL, that's only 1 gram per liter! And since most people have 4-6 liters of blood in the body, we're talking about 6g of sugar....total. Since person 2 only has a blood sugar of 70 mg/dL, they have 30% less sugar (1.8g less) in the blood to be used as energy before fat is used At 4 Calories per gram, we're talking about a 7.2 Calorie difference. That's less than a single gram of fat difference.

Now, I know what people in prep are thinking; "Even if it's a small difference, I want to do everything 100%!"

Well, let's say you do a 16 week prep....hitting fasted cardio 6 days a week for all 16 weeks....and bumping it to 7 days a week for a full month.
That's 100 sessions of cardio. At 1.8g more sugar being burned per session, that's 180g of sugar being used for energy that could have been used as fat.How many Calories is 180g of sugar? It's 720 Calories.
So how much of a difference in fat is that?

Assuming there's around 3500 Calories in pound of fat (there's probably more, a direct conversion of 9 Calories per gram gives around 4,000 Calories), that's 0.2 pounds of fat difference.

How much difference does 0.2lb of fat make?

Assuming you're dropping around 2lbs of fat per week, that's one day of fat difference--or a difference that isn't noticeable in the mirror, and is completely overshadowed by the difference water manipulation will make.