#569: The History of Fat, Cholesterol & Heart Disease

Introduction to this Episode

Few topics in nutrition generate as much confusion, or as much passionate debate, as the link between saturated fat, blood cholesterol, and heart disease. While public narratives have shifted dramatically in recent years, with some voices claiming saturated fat was unfairly demonized or that LDL cholesterol “doesnʼt matter,” the actual scientific evidence tells a far more consistent story.

This episode offers a comprehensive exploration of how dietary fat became central to our understanding of cardiovascular risk. Tracing the arc from early post-WWII observations to tightly controlled metabolic ward studies in the 1950s, it walks through landmark research by Ancel Keys and others, into the robust modern evidence from randomized trials, population studies, and mechanistic data. The episode explains how scientists uncovered the powerful influence of saturated fat on blood cholesterol levels and how that, in turn, impacts atherosclerosis and cardiovascular disease.

Importantly, it also highlights how scientific focus sharpened over time, moving from total cholesterol to LDL cholesterol and eventually apoB-containing lipoproteins, as our understanding of the atherosclerotic process deepened. What emerges is a remarkably consistent finding: diets high in saturated fat raise cholesterol and drive heart disease, while replacing saturated fat with unsaturated fat lowers cholesterol and reduces risk. This forms the backbone of the diet-heart hypothesis and continues to shape current dietary guidelines.

In an era of conflicting dietary narratives, revisiting this robust and evolving body of evidence is essential. Cardiovascular disease remains the leading cause of death globally, and LDL cholesterol is a major modifiable risk factor. Understanding the science behind dietary fatʼs role in heart disease helps clarify why guidelines exist and why claims that saturated fat is harmless donʼt hold up to scrutiny.

This episode also tackles persistent myths: that the dangers of saturated fat were invented by the sugar industry, or that modern nutrition guidelines are based on flawed or outdated science. With clear explanations, historical context, and reference to rigorous data, the conversation helps health professionals and informed listeners cut through the noise and evaluate dietary advice with clarity and confidence.

Useful Terminology for this Episode

• Metabolic Ward Study – A tightly controlled nutrition experiment where participants live in a research facility (ward) so that all their food intake can be strictly measured and regulated. Such studies allow scientists to directly observe how specific diet changes (e.g. varying types of fat) affect biological measures like blood cholesterol under controlled conditions.
• Saturated Fatty Acids – A type of dietary fat predominantly found in animal-based foods (e.g. butter, lard, fatty meats, full-fat dairy) and some tropical plant oils (coconut oil, palm oil). Chemically, saturated fats have no double bonds in their fatty acid chains.
• Polyunsaturated Fatty Acids (PUFAs) – Fats found mainly in plant oils (such as soybean, corn, safflower, and sunflower oils), nuts, seeds, and seafood. Chemically, PUFAs have multiple double bonds in their fatty acid chains.
• Apolipoprotein B (ApoB) – The primary protein embedded in LDL and other atherogenic lipoproteins (VLDL, IDL, lipoprotein(a)). Each atherogenic lipoprotein particle contains one ApoB molecule, so ApoB is an index of the number of atherogenic particles in circulation.
• P:S Ratio – The ratio of polyunsaturated fat to saturated fat in oneʼs diet. A higher P:S ratio means a diet relatively rich in polyunsaturated fats and lower in saturated fats, which tends to produce lower total and LDL cholesterol levels. Conversely, a low P:S ratio (diet high in saturated fats and low in PUFAs) leads to higher cholesterol levels.