“How the Low-Fat Craze Hijacked Our Health—and Buried a Proven Weight-Loss”

Science” PSMF as a named, clinical approach was developed and popularized in the 1970s by clinicians (notably Bruce Bistrian and colleagues at Harvard) as a medically supervised, very-low-calorie, high-protein protocol designed to rapidly lose fat while preserving lean mass. The core ideas (fasting to induce fat loss while protecting protein) have older roots in starvation and fasting research, but the formal PSMF is a later, clinical refinement. Over time, the approach was adapted to emphasize lean protein, micronutrient repletion, and medical monitoring, so it became a safe short-term option for selected patients. Meanwhile, Ancel Keys’ mid-20th-century work and the rise of the diet–heart hypothesis (1960s–1970s) shifted dietary guidance toward low-fat messages—a shift that influenced how clinicians and the public judged high-fat or very-low-carb strategies and affected how some clinicians framed or critiqued PSMF. BMJ Evidence-Based Medicine+3Gwern+3Meatrition.com+3

How the War on Fat Damaged World Health—And Distorted Decades of Nutrition Science

For thousands of years, humans thrived on diets rich in natural fats, proteins, and whole foods. Yet in the mid-20th century, a single scientific hypothesis flipped global dietary advice on its head—and the consequences have been catastrophic.

This is the story of how fat was wrongly villainised… how that error reshaped modern nutrition… and how it distorted the understanding of profoundly effective strategies like the Protein-Sparing Modified Fast (PSMF).

1950s–1960s—the diet-heart hypothesis and the fat panic

• Ancel Keys and collaborators argued that saturated fat (and resultant blood cholesterol elevations) was strongly associated with coronary heart disease. His Seven Countries Study (and earlier analyses) helped push public health advice toward lowering saturated fat intake. This created a lasting cultural and policy movement in favor of lower-fat eating that dominated dietary guidance through the late 20th century. The Keys era changed how clinicians and the public perceived fat in diets. Wikipedia+1

The Forgotten Origins: What Early Science Actually Showed

In the early 20th century, physiologists studying starvation discovered a remarkable truth:

When carbohydrates are scarce, the body safely switches to burning fat. This fat-burning state fuels the brain, preserves muscle, stabilizes blood sugar, and reduces inflammation.

Nothing in early metabolic science ever suggested that dietary fat was harmful.

So what changed?

1950s–1970s: The Birth of the Fat-Phobic Era

Physiologist Ancel Keys promoted the idea that saturated fat caused heart disease. His theory—the diet-heart hypothesis—became the backbone of global nutrition policy.

Despite major limitations in his research, the following happened:

• Governments launched low-fat food guidelines
• Doctors were taught to fear fat
• The food industry replaced fat with sugar
• Consumers were told cholesterol was deadly
• “Low-fat” became synonymous with “healthy.”

This single shift triggered a multi-decade nutritional disaster.

How Removing Fat Damaged Global Health

1. The obesity epidemic exploded

Low-fat foods are unnaturally high in sugar and extremely low in satiety, causing overeating and constant hunger.

2. Diabetes rates soared

Refined carbohydrates cause large insulin spikes—something fat never does.

3. Hormonal health collapsed

Fat is essential for:

• testosterone
• estrogen
• thyroid hormones
• leptin (satiety)
• ghrelin (hunger regulation)

Removing fat disrupted every one of these systems.

4. Heart disease did NOT improve

Despite reducing fat, heart disease remained the number one killer.

5. Food addiction and binge eating increased

Fat satisfies. Sugar triggers dopamine. The low-fat era shifted eating patterns toward addictive behavior.

The Overlooked Victim: PSMF and the Distortion of Diet Science

While the world was gripped by fat-phobia, researchers in the 1970s—led by Harvard’s Dr. Bruce Bistrian—were developing a powerful metabolic intervention:

The Protein-Sparing Modified Fast (PSMF)

A medically supervised protocol designed to:

• rapidly reduce body fat
• preserve lean muscle
• support electrolytes and micronutrients
• stabilise metabolism
• improve surgical readiness and cardiometabolic risk

It was built on fasting physiology—not fat fear.

But due to the low-fat ideology of the time, early PSMF practice was shaped—and in many ways restricted—by the belief that all fat must be avoided.

This forced clinicians to:

• Emphasise extremely lean protein
• Limit fats even when unnecessary
• frame fat as risky rather than essential
• distance the protocol from anything resembling higher-fat strategies

In short, the war on fat distorted the evolution, explanation, and acceptance of PSMF.

Today: The Science Has Corrected Itself

Modern research confirms:

✔️ Fat is not the enemy. ✔️ Sugar and refined carbohydrates drive metabolic disease. ✔️ Hormones depend on fat. ✔️ Satiety depends on fat. ✔️ Ketosis is a natural, therapeutic metabolic state. ✔️ Properly supervised PSMF is safe, effective, and physiologically sound.

Nutrition is finally returning to what human biology always knew:

Fat sustains us. Sugar harms us.

The tragedy is that it took over 60 years—and millions of cases of obesity, diabetes, fatty liver, and chronic illness—before science began undoing the damage of the low-fat revolution.

THE BOTTOM LINE

The war on fat reshaped global health—and not for the better. It misled doctors, policymakers, and the public. It corrupted food systems and created generations of metabolic dysfunction. It distorted the early reception and evolution of powerful tools like PSMF.

But the truth has returned.

✔️ Healthy fats heal. ✔️ Whole foods nourish. ✔️ Metabolic flexibility matters. ✔️ High-protein, low-carb, and ketogenic patterns support human physiology. ✔️ PSMF remains one of the most effective medical tools for rapid fat loss when properly supervised

After half a century of misinformation, the world is finally rediscovering how the human body was designed to eat.