Why High-Fat and High-Carb Together Break Your Metabolism

🌀 The Metabolic Trap No One’s Talking About: How High-Fat + High-Carb Created a Modern Swampland

For decades, we’ve swung on the nutritional pendulum—from the sugar-fearing keto camp to the cereal-clinging standard American diet. Each side claims dominance. But what if neither is right—and both are part of the same metabolic trap?

In her provocative article "In Defense of Low-Fat," Denise Minger delivers a powerful insight: the real culprit behind modern metabolic disease isn’t carbs or fats alone—it’s the toxic combination of both. She describes our modern diet as:

“...the macronutrient ‘swamp land’ ... a toxic combination [of] very processed carbohydrates with industrial vegetable oils..."

That "swampland" isn’t just metaphor—it’s a metabolic dead zone. Dense with both fat and sugar, sludge-thick with excess calories, and stagnant with the confusion of dual-fuel overload, it has left millions inflamed, fatigued, and hormonally dysregulated.

from https://deniseminger.com/2015/10/06/in-defense-of-low-fat-a-call-for-some-evolution-of-thought-part-1/

🌀 The Metabolic Trap No One’s Talking About: How High-Fat + High-Carb Created a Modern Swampland

As Denise illustrates in her now-iconic diagram, the "magic" of dietary healing happens on either end of the fat spectrum—very low fat (<10% of calories) or very high fat (>65%). But in the middle, where most modern diets live, lies the metabolic danger zone. This is where processed carbs meet industrial fats, and where dysfunction takes root.

It’s worth noting that not everyone responds to this middle ground the same way. Cultures like the French, for example, often appear metabolically resilient even with a diet that includes upward of 30% of calories from fat. Why? Because their fat tends to come from traditional sources—like butter and cream—not industrial seed oils. Their diets also lack the decades of metabolic insult common in America: no childhood Pop-Tarts, no seed-oil-laced crackers in preschool, no 20-year history of low-fat processed diet foods and metabolic suppression.

In short: they aren’t broken. Americans, on the other hand, are exiting decades of metabolic damage—PUFA overload, stress, under-eating, low thyroid, and insulin resistance. We don’t tolerate the swamp nearly as well.

⚠️ Dual Fuel Disaster: The Real Root of Metabolic Breakdown

Human metabolism is designed to be flexible, but not omnivorous at the extremes. Carbohydrates and fats use distinct entry points into the mitochondria: glucose enters glycolysis and is funneled into the Krebs cycle, while fats undergo beta-oxidation before converging on the same pathway. This means the body can either be in a carb-burning mode or a fat-burning mode—but not both simultaneously without creating metabolic friction.

When both substrates are present in abundance, the cell prioritizes glucose oxidation and stalls fat oxidation. The excess fats, especially polyunsaturated and industrial oils, are stored or shuttled into ectopic fat depots like the liver and pancreas. This leads to mitochondrial overload, oxidative stress, and inflammatory signaling that disrupts insulin sensitivity and thyroid conversion.

This is why metabolic diseases like type 2 diabetes, non-alcoholic fatty liver, PCOS, and obesity often arise from diets high in both refined carbs and fat—not one or the other alone.

🥶 Keto: A Temporary Relief, Not a Long-Term Fix

Keto works in the short term by removing the metabolic conflict. With glucose absent, the body switches fully to fat-burning mode. This can temporarily relieve blood sugar swings, reduce inflammation, and support weight loss.

But long-term carb restriction triggers adaptations that come at a cost:

• T3 (active thyroid hormone) decreases, slowing basal metabolic rate.

• Leptin and insulin signaling decline, increasing appetite and impairing fertility.

• The gut microbiome shifts, often reducing diversity and impairing motility.

• The body becomes glucose-intolerant—not because carbs are bad, but because it's been forced to adapt to their absence.

Women are particularly sensitive to these stress signals due to higher progesterone requirements, lower muscle mass, and complex reproductive needs. Eventually, signs like cold extremities, hair thinning, low libido, and cycle irregularity creep in.

Keto doesn’t cure the swamp—it just relocates you to the other end of the map.

🌿 Our Ancestral Template: High-Carb, Low-Fat—and Thriving

Evolutionarily, carbohydrates were abundant in most human environments. Wild fruit, starchy tubers, honey, and seasonal plant foods formed the core of many diets. Fat—especially in large quantities—was rare. Wild animals, particularly in warm climates, carry very little body fat. Even large ruminants like elk or bison offer mostly lean meat with limited fat stores.

Anthropological evidence and metabolic logic suggest our physiology was shaped around a carbohydrate-dominant, low-fat intake pattern:

• High-carb intake supports active thyroid hormone levels and thermogenesis.

• It boosts serotonin and progesterone production, stabilizing mood and cycle health.

• It facilitates efficient bile flow and digestive motility.

• It allows for higher total calorie intake with less fat storage, due to low respiratory quotient interference.

In contrast to today’s abundance of deep-fried starches, our ancestors did not dip tubers in seed oils or chase fruit with cheese. They ate clean-burning carbs with lean protein and tiny amounts of natural fat—and thrived.

🚪 Getting Out of Swampland Mode: The Case for High-Carb, Low-Fat

Modern metabolic dysfunction is not about “too many carbs” or “too much fat.” It’s about the chronic coexistence of both in hyper-palatable, processed forms. Bagels with cream cheese, fries in soybean oil, donuts, pizza—each is a swamp trap.

The escape isn’t restriction. It’s selectivity. Choose your primary fuel and stick with it.

The pro-metabolic approach favors high-carb, low-fat eating because it restores the body’s default operating mode:

• Glucose fuels the brain, liver, muscles, and reproductive tissues with precision.

• Insulin works efficiently to shuttle nutrients into cells.

• The liver clears estrogen and metabolizes thyroid hormones optimally.

• Digestion becomes robust again, especially when fat intake is low enough to allow consistent bile turnover.

When you stop asking your body to juggle dueling fuels, it finally gets to perform.

💡 Bottom Line: Choose the Right Fuel—Not All of Them

We’ve spent decades playing metabolic whack-a-mole—vilifying carbs, then fat, then sugar, then meat. But the true villain is the swamp in the middle: high-fat, high-carb chaos with no clear energy direction.

If you want to heal your metabolism, ditch the swamp. Pick a side—and if you’re seeking long-term repair, radiant warmth, stable hormones, and metabolic flexibility, high-carb, low-fat is your best bet.

Eat like your ancestors: fresh fruit, honey, roots, squash, lean meats, gelatin, dairy, and a touch of natural fat.

This isn’t a fad. It’s human physiology done right.

Time to rise from the swamp—and run hot again. ✨