But Your Cholesterol, Your Heart...
A Metabolic state in which the body burns fat rather than glucose for fuel. Characterised by a measurable level of ketone bodies in the blood. → more diet is high in fat, moderate in protein, and low in carbohydrates.
One of the most common questions I get is: “What about your cholesterol? Doesn’t that cause problems for your heart?”
No, it doesn’t. And there’s a whole pile of studies, findings, reports, and mechanisms that have led me to consider other blood markers better suited to judging my heart health than “the bad cholesterol”.
Books
Since I have no intention, with this article, of giving anyone the chance to say “but the internet said…”, for very many aspects I’ll point to the sources - in this section, books - that have reinforced this view of mine, and to which I owe a good deal of my understanding of metabolism:
Nina Teicholz’ “The Big Fat Surprise” (1) tells a gripping history of fat phobia and dietary advice, plus a mountain of references. In fact, the book contains so many well-researched references that the author later developed it into her doctoral thesis(2). It’s an excellent read even without a scientific background.
An intriguing side note: before this book the author was a vegetarian, lived low-fat, and through the research for it completely changed her convictions.
Gary Taubes’ very medical “Good Calories, Bad Calories”, along with the more accessible “Why we get fat and what to do about it” (3), did the rest. These, too, come with very good scientific references.
Both Nina Teicholz and Gary Taubes are science journalists, which explains how readable the books are (in Gary Taubes’ case, especially the second one) for non-scientists.
But also further articles and studies published in the specialist literature - and, where relevant, the responses to them:
Straight from the science
And although it contains no health findings as such, but instead documents how research into cholesterol and heart health was corruptly influenced back in the 1960s: the work of Kearns et al, “Sugar Industry and Coronary Heart Disease Research: A Historical Analysis of Internal Industry Documents” (4), which laid out just how intensively (in aim, method, result, and funding) the sugar industry shaped the research to make sure fat got the blame, while sugar - as commissioned and (provably) paid for - got the all-clear.
The origin of fat phobia
And then there was the origin of fat phobia (as I’ve pieced it together), Ancel Keys' “Diet-Heart-Hypothesis”. His publications tend to get muddled up: an early publication of data from 6 countries showed a neat correlation between fat consumption and heart disease. Except that he had data from 22 countries, and picked exactly the ones that best showed a correlation. He followed up with a Seven Countries Study (5), which was likewise heavily criticised, among other things for the selection of countries. The German-language Wikipedia article has a “Criticism” section that’s missing from the English one. That section links a white paper defending the Seven Countries Study - which itself did not go uncontested or unrefuted. I’ll link Part 1 of the very readable pair of articles by Zoe Harcombe refuting that white paper (6).
The study that can say anything
The so-called “Framingham Study” (7) is cited by supporters and opponents of the cholesterol-heart hypothesis alike. To me, that’s less a contradiction than a symptom.
It’s a cohort study running since 1948 - that is, a purely observational study, which can reveal associations but not causes. And a study that gathers data across more than 75 years, several generations, and countless subgroups produces so many correlations that, with the right slice, you can support almost any thesis. The longer and larger the study, the bigger the trove both sides can draw from.
The data serve up two glorious bombshells that send the anti-cholesterol camp’s dogmatic house of cards wobbling. Careful: they prove nothing - they merely show how little the simple chain “fat -> cholesterol -> heart attack” actually holds up:
First, a line from William Castelli, the study’s director at the time, from a 1992 editorial (8): “In Framingham, those who ate the most saturated fat, cholesterol, and calories had the lowest serum cholesterol - and they weighed the least and were the most active”. (I’m quoting second-hand here on purpose; I haven’t read the original myself.)
Second, an analysis over 30 years of follow-up (9): in the under-50s, higher cholesterol did indeed correlate with higher mortality. Over 50, it no longer did - and, more curious still, cholesterol that fell over the years went hand in hand with higher mortality.
Before anyone misreads that as “low cholesterol is dangerous”: the authors themselves point out that cause and effect are probably reversed here - someone whose cholesterol is dropping is often already ill. And that’s exactly the point: even the study’s authors handle their own correlations more cautiously than the headlines ever did.
What remains isn’t a counter-proof but a sobering thought: a single observational study, however large and long-lived, does not settle this question. Anyone citing it as proof - for either side - has usually just picked the slice that suited them.
My conclusion from all this
Let me put it this way: I’m no scientist - least of all in the field of nutrition. But by now I’ve dug into this so deeply that my takeaway is this: the classic dietary advice and guidelines feel to me like a set of disconnected definitions. There are many things you have to weigh and account for independently of one another:
- Oats are always great - except sometimes (e.g. with diabetes) they’re to be used a bit more cautiously.
- saturated fats are to be avoided - except as the metabolic by-products of gut bacteria
- the overweight should lose weight - but fat burning (ketosis) gets labelled a derailment (10)
- what matters is eating fewer calories than you burn (but no one manages lasting success that way and stays healthy - the reversal of cause and effect is more helpful)
The books quoted above, together with the publications and the debates around the studies listed here, have equipped me with an understanding of metabolism that doesn’t depend on definitions: ever since I learned that eating against the guidelines can also work very well, and has a scientific basis, I understand the principles, so that only very few definitions are needed at all.
Paired with my own experience of a ketogenic - and later low- to zero-fibre - diet, the apocalyptic consequences that classic nutritional teaching deems inevitable really ought to have shown up at some point over the past 14 years. Spoiler: They didn’t.
That’s it - I still have butter to thaw.
