THE FOOD · INVESTIGATION
Fat: why were
we always so
afraid of
you?
For decades, fat was the first thing to go.
Now olive oil gets its own aisle. What changed?
There was a stretch of time — roughly the 1980s through the early 2000s — when fat was public enemy number one.
Fat-free cookies. Fat-free yoghurt. Salad dressing that was mostly sugar, proudly stamped "97% fat free."
Supermarket shelves filled up with foods engineered to remove fat and replace it with something else, usually refined starch or sugar, so the product would still taste like something.
And then, slowly, the story flipped.
Olive oil started showing up in "healthy" recipes by the tablespoon. Avocados became a brunch centrepiece. Butter came back from exile. Full-fat yoghurt started outselling the low-fat kind on "wellness" shelves.
was actually true?
Before picking a side, I wanted to know something more basic.
What is fat actually doing in my body?
What even
is fat?
Dietary fat, chemically, is mostly made of triglycerides: a glycerol backbone with three fatty acid chains attached.
Along with carbohydrate and protein, fat is one of the three macronutrients — and it's by far the most energy-dense one, providing roughly 9 kcal per gram, more than double what carbohydrate or protein provide.
stored energy.
Fat forms part of the membrane around every one of your cells. It's a key ingredient in several hormones. It cushions and protects your organs, and helps insulate your body.
It's also the only way your body can absorb and transport vitamins A, D, E and K — the fat-soluble ones. Eat a completely fat-free salad and you'll absorb noticeably less of the vitamin A in those vegetables.
Which makes "fat-free" a strange thing to put on a food whose whole job, sometimes, is delivering fat.
NOT ALL FAT BEHAVES THE SAME WAY
Saturated. Unsaturated.
Trans.
Saturated
Found mainly in animal foods — butter, fatty meat, cheese — and a few plant oils like coconut and palm oil. Solid at room temperature. The fat most guidelines suggest eating less of.
Unsaturated
Found in olive oil, nuts, seeds, avocados and fatty fish. Usually liquid at room temperature. Split into monounsaturated and polyunsaturated, including the essential omega-3 and omega-6 fats.
Trans
Mostly created industrially by hardening vegetable oil. Raises "bad" LDL cholesterol and lowers "good" HDL cholesterol at the same time — a combination none of the other types manage.
Three names, three very different stories. Lumping them all together as "fat" is a bit like lumping olive oil, margarine and lard into one drawer and hoping for the best.
THE OFFICIAL RANGE
So how much
fat do we
actually need?
The European Food Safety Authority sets a reference range of 20 to 35% of total energy from fat for adults — wide enough that very different-looking diets can sit comfortably inside it.
of energy from saturated fat
The WHO's guideline figure — with trans fat kept under 1%, and ideally close to zero.That last part matters more than it might sound. In 2018, the WHO launched REPLACE, a global initiative aimed at eliminating industrially produced trans fat from the food supply entirely — not just reducing it, removing it.
Unsaturated fat doesn't get a strict ceiling, partly because it includes the two families of essential fatty acids — omega-3 and omega-6 — that your body cannot make on its own and has to get from food.
So the useful question probably isn't:
"How do I get my total fat number down?"It's:
"Which kind of fat is most of mine actually coming from?"HOW WE GOT HERE
The guideline
flip-flop.
US Dietary Goals urge Americans to cut fat sharply, kicking off decades of "low-fat" as the default healthy-eating advice.
Fat-free products boom. Some of the fat they replace gets swapped for industrially produced trans fat — at the time seen as a neutral, shelf-stable substitute.
US dietary guidelines drop their 40-year limit on dietary cholesterol, concluding it isn't a "nutrient of concern" for most people.
The WHO launches REPLACE, targeting full global elimination of industrial trans fat — the clearest fat villain turns out to be the newest one.
None of this means nutrition science keeps getting it wrong. It means the evidence on fat has genuinely gotten more specific over time — less "fat, yes or no," more "which fat, replacing what."
TWO MYTHS, RETIRED
The claims that outlived
their own evidence.
THE MYTH
"Eating fat makes you fat."
THE EVIDENCE
Fat is calorie-dense, at roughly 9 kcal per gram, so it's easy to overeat by volume. But the low-fat era didn't shrink waistlines — obesity rates kept climbing through the years fat-free products dominated supermarket shelves.
Body weight tracks overall energy balance, not any single macronutrient. Plenty of higher-fat diets outperform low-fat ones in weight-loss trials, largely because they tend to be more filling.
THE MYTH
"Eggs are dangerous for your heart."
THE EVIDENCE
For 40 years, US dietary guidelines capped dietary cholesterol at 300mg a day — about two eggs' worth.
In 2015, that limit was quietly dropped. The evidence showed dietary cholesterol has little effect on blood cholesterol for most people — your liver adjusts its own production to compensate. Saturated fat and the overall dietary pattern turned out to matter more than the cholesterol content of any single food.
THE QUESTION I ACTUALLY CAME FOR
Okay, but should
I go low-fat?
We've established that fat isn't one thing, that the villain of the story turned out to be an industrial invention, and that "fat-free" was never quite the win it was sold as.
Which brings us to the question that probably started this whole investigation.
The logic sounds good.
The trials say otherwise.
The case for low-fat eating usually goes like this:
One of the largest dietary trials ever run puts that logic to a real test.
Over 7,400 adults at high cardiovascular risk were randomly assigned to a Mediterranean diet supplemented with extra-virgin olive oil, a Mediterranean diet supplemented with nuts, or a standard low-fat diet. After roughly five years, the olive oil group had about 31% fewer major cardiovascular events than the low-fat group.
This is a randomised trial, not just an observed pattern — one of the strongest kinds of evidence nutrition science can produce. And it points the opposite direction from "just eat less fat."
CONTEXT MATTERS
So when does watching fat intake actually make sense?
Managing an existing cardiovascular condition, under a doctor's guidance
Conditions that affect fat digestion or absorption
Specific medical diets, such as a ketogenic diet prescribed for epilepsy
Infants and young children, whose growing bodies need a higher proportion of fat than adults
Athletes with specific, high energy demands
The less useful question is:
"How do I get fat out of my diet?"The more useful one is:
"Is the fat I'm eating mostly the industrial kind, or the olive-oil-and-almonds kind?"For most people, that second question does almost all of the useful work.
SO, WHAT DID I ACTUALLY LEARN?
Probably not what
the 90s promised.
I started this expecting a cleaner story: fat is either the thing to cut or the thing to embrace.
Instead I found a macronutrient that got blamed for decades, largely replaced by sugar and refined starch in the process, while the actual villain — industrially produced trans fat — was busy hiding in the very products marketed as the healthy swap.
Favour unsaturated fat — olive oil, nuts, seeds, fatty fish — over saturated and, especially, trans fat.
Don't fear fat as a category just because it's calorie-dense.
Pay attention to what a "low-fat" product replaced the fat with.
Not a nutrient to strip out of your diet.
Not a free pass to eat any fat in any amount.
Just a macronutrient with better and worse members, like the other two.
AND MAYBE THAT'S THE PART I WAS LOOKING FOR
Understanding gives us
better questions to ask.
I don't think the lesson of fat is that we finally picked the right side.
I think it's that "fat" was never specific enough to be either a villain or a hero — the details underneath the word were doing all the actual work.
"Should I be eating less fat?"
becomes"Is most of my fat coming from whole foods or from industrial processing?"
"What am I actually replacing it with when I cut it?"
"Does this apply to me specifically, or to nutrition advice in general?"
And if the answer is that your olive oil, your nuts and your salmon were never the problem?
stay in the 90s.
Because nutrition is supposed to exist within our lives.
Not become another decade-long overcorrection we have to quietly walk back.
I went into this half-expecting to come out with a reason to keep measuring tablespoons of oil. Instead, I came out cooking with more of it — and reading ingredient lists a little more closely for the word "hydrogenated."
Don't fear a whole macronutrient over one bad decade.
READ THE EVIDENCE
Sources
- European Food Safety Authority (2010). Scientific Opinion on Dietary Reference Values for fats, including saturated fatty acids, polyunsaturated fatty acids, monounsaturated fatty acids, trans fatty acids, and cholesterol.
- World Health Organization (2018). Guideline: Saturated Fatty Acid and Trans-Fatty Acid Intake for Adults and Children — and the REPLACE initiative.
- Estruch, R., et al. (2018). Primary Prevention of Cardiovascular Disease with a Mediterranean Diet Supplemented with Extra-Virgin Olive Oil or Nuts. New England Journal of Medicine (PREDIMED trial).
- U.S. Department of Health and Human Services & U.S. Department of Agriculture. 2015–2020 Dietary Guidelines for Americans, 8th Edition.