By Ariaratnam Gobikrishna –

Ariaratnam Gobikrishna MD

Science has always been a moving goalpost. New data emerge, old assumptions are challenged, and recommendations shift accordingly. In that spirit, dietary guidelines are revised every five years. As usual, panels of scientists deliberate and produce consensus statements. Lawmakers then interpret, and reshape those conclusions into policy language.

In the 2025–2030 guidelines, refined carbohydrates and ultra-processed foods are cast as villains—although previous guidelines never endorsed them, they never explicitly denounced them either. Meat and dairy are rehabilitated as “real food,” occupying the broad top of the inverted pyramid, while the familiar 10 percent ceiling for saturated fat is tucked away in the fine print. Whole grains are relegated to the narrow tip, visually downplayed even as their benefits are praised in the text.

But the essential questions remain: are we pursuing the best possible dietary pattern based on the totality of evidence — or simply choosing the lesser of two flawed extremes? Is saturated fat from meat and dairy truly healthful for everyone? Or were we misled for decades into believing it was harmful?

So how did we arrive at such diametrically opposing conclusions in the first place?

In the early 1950s, North America was confronting an alarming rise in premature cardiovascular deaths. Into that uncertainty stepped Ancel Keys, a physiologist who sought to understand why some populations had far lower rates of coronary heart disease than others. His work culminated in the landmark Seven Countries Study, which examined dietary patterns and heart disease rates across the United States, Northern Europe, and Mediterranean regions.

His early hypothesis focused more broadly on total fat intake and serum cholesterol. Over time, as data accumulated, the emphasis narrowed toward saturated fat. Populations in Mediterranean regions, where total fat intake could approach 40–45% of calories — largely from unsaturated olive oil and other plant sources — had markedly lower rates of heart disease than countries such as Finland, where saturated fat intake from animal sources was high and cardiovascular mortality was among the highest in the world.

So where did we go wrong?

Armed with this knowledge, in the late 1970s and early 1980s, dietary guidance advised limiting total fat to about 30% of calories and saturated fat to about 10%, replacing the remainder primarily with carbohydrates and a modest proportion of protein. On paper, this macronutrient distribution appeared scientifically sound. In practice, however, it was exceedingly difficult to implement — even for dietitians — let alone for the general public.

Compounding the problem, organizations such as the American Heart Association scientifically distinguished saturated fat from unsaturated fats, but that difference did not always translate clearly into public messaging. The potential benefits of unsaturated fats — particularly polyunsaturated fats — were slower to gain prominence in simple consumer guidance. As a result, the recommendation was often distilled in the public mind into a blunt slogan: fat is bad.

Consequently, total fat intake—particularly saturated fat—declined modestly, which some credit with falling cardiovascular disease rates. Yet attributing the drop in coronary deaths primarily to diet oversimplifies the picture. This occurred long before the advent of statins and the campaign against trans fat. Simultaneously, major public health advances unfolded: anti-tobacco campaigns gained traction, hypertension was treated more systematically, and coronary care units expanded across hospitals. Coronary heart disease mortality therefore declined due to a convergence of medical and societal changes, not diet alone.

Into this landscape stepped the food industry with a new marketing slogan: low-fat, heart-healthy, convenient options. With this mantra, total caloric intake rose substantially over the ensuing decades, fueled largely by refined starches and added sugars. The result was not a healthier population, but a food environment dominated by ultra-processed products carrying health hazards, increasing the incidence of metabolic diseases through the explosion of obesity.

Thus, America entered a period of deep nutritional chaos. The rapid decline in cardiovascular mortality began to plateau, even as metabolic diseases and certain cancers rose in parallel with the explosion of obesity. People began searching not only for answers, but for scapegoats.

The most convenient target became the message and the messenger — particularly Ancel Keys and the so-called fat hypothesis. It was far easier to blame a decades-old dietary recommendation than to confront the structural transformation of the food environment. Few were willing to directly challenge the power and pervasiveness of the ultra-processed food industry. Instead, the battle shifted to macronutrients.

Carbohydrates and seed oils were blamed. Wheat and other grains came under attack, gluten in particular. Dairy was vilified. Then all animal products. Some promoted small, frequent meals to “stoke metabolism.” Others advocated intermittent fasting, time-restricted feeding, prolonged water fasts. The list expanded endlessly.

But we are no longer in the era of Ancel Keys. Today, we have randomized controlled trials, long-term follow-up studies, and meta-analyses rather than relying primarily on observational epidemiology. And what does this modern body of evidence show? Ironically, it largely converges on conclusions similar to those advanced by Ancel Keys decades ago. Dietary patterns such as the Mediterranean diet and its close relative, the DASH (Dietary Approaches to Stop Hypertension) diet, consistently rank at the top for cardiovascular and overall health outcomes.

These patterns emphasize predominantly plant-based foods, generous use of unsaturated fats (particularly olive oil and nuts), regular consumption of fish, moderate intake of poultry, limited red meat, modest dairy, reduced sodium, and minimal ultra-processed foods. The answer is no longer mysterious. It boils down to something simple: eat real food, mostly plants, not too much; use salt sparingly, and drink water to quench thirst.

It is simple, but it is not glamorous. It requires time, persistence, and a profound shift in entrenched eating habits. America, however, has never been patient. It prefers visible results, and it prefers them quickly.

Enter the ketogenic diet

Dropped into the midst of metabolic dysfunction, it works — at least initially — like a charm. Carbohydrates are sharply restricted, weight falls rapidly, appetite is blunted, triglycerides decline, glucose improves, and inflammatory markers often move in the right direction. For individuals coming from a background of ultra-processed, high-refined-carbohydrate eating, the contrast can feel transformative. Many report that they have never felt better.

But there is another side. Strict ketogenic diets can drive LDL cholesterol upward, sometimes into the 200 mg/dL range or higher in lean individuals. The central questions still remain: Is the diet sustainable over long term? And what does persistently elevated LDL mean for arterial health over time?

Around this tension, a movement formed. It professed the following: if inflammation is reduced, LDL becomes an innocent bystander. High LDL in the context of low triglycerides and good glycemic control was rebranded as benign or even beneficial. The LDL hypothesis itself was declared obsolete. A cadre of social media physicians amplified this message to millions, often cast as challenging big pharma.

To bolster the claim, a single small observational study was presented as proof. It examined a group of metabolically healthy adults with very high LDL — labeled “lean mass hyper-responders” — and followed them for one year using coronary CT angiography to assess plaque changes. The time frame was short, the cohort small, and there was no control group for comparison. Atherosclerosis is a chronic process that typically unfolds over years, especially in otherwise healthy adults.

Yet, to many observers’ surprise, the study did not demonstrate plaque stability or regression. Instead, it showed new development and progression of noncalcified (soft) plaques, even over that brief period. This raised concern within the medical community. However, that was not the message amplified in the media. The findings were framed instead as reassurance — as though the results supported the claim that high LDL in this context was harmless. And once such a message spreads, it is extraordinarily difficult to retract. The narrative is emotionally compelling: you can keep your eggs, bacon, sausage, steak, butter, and lard — and be told that not only are they safe, but they are virtuous. For many, that validation is irresistible.

Similarly, the PURE study, often cited by carnivore diet proponents, was not a randomized trial but an observational study conducted across low-, middle-, and high-income countries. It reported lower mortality with higher fat and animal protein intake and higher mortality with greater carbohydrate intake. However, many of the high-carbohydrate diets consisted largely of refined staples, trans fats were not measured, and dietary data came from a single questionnaire, making it likely that the apparent advantage of animal foods reflects poor diet quality and socioeconomic factors rather than true superiority.

Then comes another camp, equally certain, arguing that anything plant-based is inherently safe. For palatability, many rely heavily on coconut and palm oils and contend that these saturated plant oils have been unfairly maligned. Anecdotes are often invoked — particularly references to Pacific Island populations — to suggest that such fats are harmless in traditional diets.

But anecdotes are not trials. What we have in abundance are laboratory studies showing that coconut and palm oils raise LDL cholesterol substantially, with modest increases in HDL. What we lack are large, long-term randomized controlled trials demonstrating that these oils are cardiovascularly safe when compared head-to-head with established unsaturated fats such as olive or canola oil. In the absence of robust outcome data, prudence would suggest caution.

Likewise, some looked to the archaeological record of Paleolithic humans, inspiring the modern Paleolithic diet movement. Yet no one truly knows what these diets were like. As both humans and their environment evolved, any reconstruction is largely speculative. Available evidence suggests short human lifespans shaped by factors beyond diet, including infection, trauma, and lack of medicine. In that sense, attempting to recreate a Paleolithic diet is more an exercise in imagination than a practical guide for contemporary life.

Look, we keep searching for exoneration — for the nutrient that will absolve us, the study that will validate our preferences, the movement that will let us keep our habits untouched. But biology is stubborn. Arteries respond to particles, not podcasts. Metabolism responds to energy balance, not slogans. And atherosclerosis – the number one killer – does not pause for ideological debates.

In the end, we are not arguing with one another.

We are arguing with biology.

And biology always has the last word.