Ben GreenfieldFounder, Ben Greenfield Life

Low-Carb vs High-Carb: The Truth About Fats, Sugar & Your Metabolism

11 Sept 2025 · 1 min

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1:05

Transcript excerpt from a YouTube discussion contrasting low-carbohydrate (high-fat/ketogenic) dietary claims and potential downsides. One speaker (Sam) argues low-carb/ketosis shifts fuel use to fats and ketones—citing a study (Murashiga) suggesting heart muscle prefers ketones/fats over glucose. The other speaker cautions that low-carb approaches can be physiologically stressful over time, reporting increases in anxiety, sleep problems, and reproductive-hormone disruptions.

Chapters

So I reverse type 2 diabetes by having people eat fat, no carbs, and they burn fat because they're not burning the sugar, they're not burning the carbohydrates, and when you cut all the carbs out. Actually, Murashiga did a system wide look at the fuel of the heart, and in the abstract he wrote, we were surprised to find the heart muscle didn't use much glucose. All he had to do was talk to professors of medicine who put ketones and fat and sugar in the heart muscle petri dish, and the ketones get sucked up by the heart first.
First, I think that there are certain aspects of the diet or the approach that are very beneficial, but there's also an underlying aspect which is inherently stressful. And over time that stress is going to accumulate. And so a lot of people who are coming to me, they're dealing with over time on these low carb diets, they're seeing increases in anxiety, trouble sleeping, decreases in reproductive hormones, you know, on the male side, testosterone on the female side, interruptions in cycles, maybe low progesterone. So those are the kinds of effects that I'm seeing, Sam.