The brain also runs well on ketones which are more energy dense and remove the oxygen bottleneck. It's easier to deliver a consistent level of ketones than glucose, avoiding spikes and crashes.
Before modernity, maintaining long-term ketosis (eg decade+ length) would have been extremely difficult. Some anti-sugar advocates portray sugar as inherently evil, suggesting that any consumption will lead to significant harm.
However, moderation is often more practical:
1. Many marathon runners use glucose gels and still enjoy long, healthy lives, typically living about 7 years longer than non-athletes.
2. Most researchers at the National Institute on Aging do not recommend avoiding all sugar or focusing solely on ketogenic diets. In fact, studies show that intermittent fasting often leads to longer lifespans than ketogenic diets.
3. New data is showing that long term ketogenic diets lead to the death of healthy cells, increased adipose tissue, increased triglycerides https://www.science.org/doi/10.1126/sciadv.ado1463