What is a better source of energy, fat or carbohydrate?
One of the major benefits of switching your metabolism over to a “fat burner” as opposed to a “sugar burner” is that people often report that they don’t have an energy crash in the afternoon. Once they are in ketosis, many people also state that they have an increased sense of well-being and much more stable energy levels. A major reason that people have these improvements is because, as we have discussed before (CLICK HERE), we can’t store very much sugar to burn for fuel. We can, however, store lots of fat to burn as fuel. We just need to keep our insulin levels low enough that we can tap fat as a resource for energy.
A burning question that I have had over the last several years is this:
Since our bodies use ATP (Adenosine Triphosphate) as the cellular energy currency, which fuel source gives us more ATP? Is it fats or carbohydrates?
The biology department over at Cornell University has done the math for us on this one. Not surprisingly it turns out that fatty acids supply 40% more energy than blood sugar. That is the kind of edge that any one of us can benefit from. What would you do with 40% more energy? Once you get yourself into ketosis and you’re burning fat for fuel, you can use that energy to drive any number of your passions.
For those who like the details, here is the report from Cornell:
A 6-carbon fatty acid has more “stored energy” than glucose (also 6 carbons) because fat metabolism will break the fatty acid into 3, 2-carbon acetyl CoA molecules, while glycolysis breaks glucose into just 2 acetyl CoAs and wastes 2 carbons in forming CO2. In producing the 3 acetyl CoAs, fatty acid metabolism also yields 1 NADH and 1 FADH2 for every pair of carbons in the fatty acid. These are fed into the electron transport chain like normal and result in the production of extra ATP by the fatty acid. The breakdown of fatty acids into acetyl CoA is called β-oxidation and occurs in the mitochondria. Interestingly, studies have shown that grizzly bears depend solely on β-oxidation of stored fats to maintain their body heat and to produce energy for other body functions during their long period of winter sleep. No wonder bears work so hard to find and consume fatty foods before winter hits!
The accounting looks like this:
|Glycolysis||2 ATP (substrate) 2 NADH (= 3 ATP)||None|
|Acetyl CoA production||2 NADH (= 5 ATP) 2 Acetyl CoA||3 NADH (= 7.5 ATP) 3 FADH2 (= 4.5 ATP) 3 Acetyl CoA|
|Krebs||2 ATP (substrate) 2 Turns 6 NADH (= 15 ATP) 2 FADH2 (= 3 ATP)||3 ATP (substrate) 3 Turns 9 NADH (= 22.5 ATP) 3 FADH2 (= 4.5 ATP)|
|GRAND TOTAL||30 ATP||42 ATP|
|5 ATP/carbon||7 ATP/carbon 40% more ATP per molecule|
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