Ketogenic Diets and the Human Face of Metabolism

Ketogenic diets have moved beyond weight control. In recent years, they have been tested in Alzheimer’s, Parkinson’s, and ALS. The idea is simple: when glucose metabolism falters, ketone bodies provide an alternative fuel. Mitochondria gain support, oxidative stress is reduced, and neuroinflammation is modulated. Small clinical trials report short‑term cognitive improvements. Animal models show preserved motor function. Yet the evidence remains limited. Larger, long‑term studies are still needed.

When I read these studies, I always think of J. Denis McGarry. He was the scientist who explained how the body balances burning fatty acids and using glucose. His work on the “malonyl‑CoA/CPT1 system” and the “vicious cycle” showed how too many fatty acids can block glucose use and lead to insulin resistance. This idea is still important today. Ketogenic diets shift the body’s energy use toward ketones and fatty acids. While this can provide energy, it may also reduce glucose use, which is important for brain functions like learning and memory. Both the hope and the challenge of ketogenic diets reflect McGarry’s legacy.

I traveled to the 2001 ADA meeting in Philadelphia for one reason: to see McGarry. He had just received the Banting Medal. But illness had caused aphasia. He could not deliver his own lecture. Bob Sherwin, then ADA President, spoke in his place, presenting McGarry’s scientific achievements with kindness and detail. My eyes, however, were fixed on McGarry himself. He stood beside Sherwin with quiet dignity, his presence stronger than words.

At the end, I made myself speak up, even though my English was not perfect, just to connect. Sherwin replied, but I do not remember what he said. What stayed with me was McGarry’s smile. That smile was enough. It was a quiet moment of understanding, a human connection in the middle of a scientific meeting.

A year later, McGarry had passed away. His model explained how fatty acids can trap glucose in a cycle that leads to disease. But his silent smile showed something more: science is done by people, and their presence matters beyond their discoveries. Ketogenic diets remind us of a similar paradox. Ketones can help provide energy, but sometimes at the cost of using less glucose. In the end, molecules help us understand disease, but a simple smile reminds us of our shared humanity.