Fat Didn't Make Us Fat.
The War on Fat
Made Us Fat.
For fifty years, dietary fat was the villain of the piece. The food industry obligingly removed it. They put sugar in its place. Then everybody got heavier and nobody seemed to notice the obvious connection.
In the mid-1970s, the United States government did something it had never quite done before: it issued official dietary guidance telling an entire nation to eat less fat. Not a specific fat. Not saturated fat in moderation or trans fat never. Just fat, as a category, as a macronutrient, as a thing. The McGovern Committee's Dietary Goals for the United States landed like a nutritional manifesto, and the food industry — alert as always to the commercial opportunities hiding inside public health guidance — moved quickly to fill the resulting shelf space with an entirely new category of product: low-fat everything. Low-fat yogurt. Low-fat salad dressing. Low-fat cookies. The SnackWell's phenomenon, in which people ate an entire box of low-fat devil's food cookies in one sitting and felt virtuous about it, was not a personal failing. It was a rational response to the signalling they had been given.
The resulting fifty-year experiment in low-fat eating produced something nobody predicted and nobody particularly wanted: a population that was, by virtually every measure, fatter and more metabolically unwell than it had been before the guidance was issued. Obesity rates climbed. Type 2 diabetes rates climbed. And fat, which had been eating the blame, sat there in the dock looking increasingly confused about the charges.
What They Put in the Fat's Place
Here is the part of the low-fat story that the original guidelines failed to adequately address, possibly because it was commercially inconvenient to address it: when you take fat out of food, food tastes terrible. Fat carries flavour, delivers satiety, creates texture, and makes the experience of eating something deeply pleasurable in a way that has been wired into human neurology over millions of years. Remove it and you have a product that tastes like cardboard seasoned with disappointment. The food industry knew this, and their solution was straightforward: replace the fat with sugar, refined starch, and salt — ingredients that could restore palatability without the macronutrient that had been officially condemned.
The low-fat yogurt that replaced full-fat yogurt frequently had more sugar per serving than the original product. The low-fat salad dressing that replaced olive oil had a longer ingredient list, a higher sugar content, and delivered the fat-soluble vitamins in the salad directly into the toilet because without dietary fat present, your body cannot absorb them. The low-fat era wasn't a reduction in caloric intake — it was a macronutrient substitution that traded a nutrient with a long history in the human diet for ingredients that were new, cheap, and turned out to have their own rather significant downstream effects on appetite and metabolic health.
They took the fat out of the yogurt and put sugar in its place. Obesity rates then climbed for thirty years and nobody connected the dots until it was very nearly too late.
The Science That Was Always There
The evidence that dietary fat was the primary driver of cardiovascular disease and obesity was, even at the time the low-fat guidelines were issued, considerably weaker than the confidence with which those guidelines were delivered. The Keys hypothesis — Ancel Keys' famous Seven Countries Study linking saturated fat intake to heart disease rates — was influential, widely cited, and methodologically compromised in ways that are now well documented: Keys had data from twenty-two countries and chose to publish results from seven, a selection that produced a much cleaner relationship between fat and heart disease than the full dataset supported. This isn't conspiracy theorising. It's a documented critique that has been in the epidemiological literature for decades.
Meanwhile, the populations that ate the most fat — the French with their butter and cheese, the Mediterranean populations with their olive oil — kept stubbornly failing to die of heart disease at the rates the fat hypothesis predicted. These inconvenient data points were explained away, folded into the French Paradox narrative we dissected on Day 6, and generally treated as anomalies rather than evidence that the core theory needed revisiting. The theory survived not because the evidence was unambiguous but because the policy infrastructure built around it — the food industry's investment in low-fat product lines, the public health messaging, the dietary guidelines themselves — had created enormous institutional momentum that anomalous data alone could not easily reverse.
Where We Actually Landed
The rehabilitation of fat in mainstream nutrition has been one of the more dramatic reversals in recent dietary science. Dietary guidelines now distinguish carefully between fat types: trans fats are unambiguously harmful and have been largely removed from the food supply; saturated fat remains a nuanced conversation where the replacement matters as much as the reduction; unsaturated fats — the kind in olive oil, avocados, nuts, and fatty fish — are not just acceptable but actively encouraged. The monolithic "fat is bad" claim that structured an era of eating has been retired, quietly and without anything approaching the public fanfare with which the original warning was issued.
What we're left with is a more complex, less convenient truth: fat is not the villain, refined carbohydrates are not innocent, and the human body does not respond to macronutrients in the simple, predictable, category-by-category way that made for clear public health messaging but turned out to be poor biology.
Rehabilitate Fat. Interrogate What Replaced It.
Full-fat dairy, avocado, olive oil, nuts, fatty fish — these are not dietary concessions. They are legitimate, evidence-supported foods that deliver satiety, fat-soluble vitamins, and flavour in a way that the low-fat alternatives they replaced never managed. The war on fat didn't make us leaner. It made us more dependent on sugar, and the food industry has been profiting from that dependency ever since.
