Are ketones a perfect fuel source?

Ketones are not considered a perfect fuel source, though they do serve important roles. Dr. Steven Gundry explains that while ketones can cross the blood-brain barrier and provide an alternative fuel to the brain, they only supply about 30% of our power during ketosis. The remaining 70% must still come from free fatty acids and glucose. Even in a state of full ketosis, the brain requires 30-40% of its energy from glucose 1.

Ketones act more as signaling molecules rather than just a primary fuel. They play a crucial role in metabolic processes by signaling mitochondria to adapt to conditions like fasting or low carbohydrate intake. This adaptability helps keep the brain functioning during tough times but suggests that ketones are more beneficial as a backup fuel source rather than a primary one 2 3.

Additionally, there's evidence that ketones are highly efficient, particularly in certain medical conditions, by improving the energy efficiency of failing hearts and brains. For instance, in heart failure or brain injuries, ketones can enhance function and efficiency, indicating their valuable role as alternative fuel in specific contexts 2.

Overall, while ketones are a valuable and efficient fuel source under certain circumstances, they are not a perfect or complete fuel source for the body's needs.