Guess what were the top reasons for human death 100 years ago, and what they are today?
In the 1920s:
- Pneumonia and Influenza
- Tuberculosis (TB)
- Diarrheal diseases
- Childbirth-related complications (especially maternal mortality)
- Infectious diseases (measles, diphtheria, typhoid, etc.)
- Malaria
- Accidents (trauma and injury)
- Heart disease (beginning to rise, but not dominant)
- Cancer (relatively rare in records, but likely underdiagnosed)
- Malnutrition (especially in children)
Today:
- Ischemic heart disease (e.g., heart attacks)
- Stroke
- Chronic obstructive pulmonary disease (COPD)
- Lower respiratory infections (e.g., pneumonia)
- Neonatal conditions (e.g., birth complications)
- Trachea, bronchus, and lung cancers
- Alzheimer’s disease and other dementias
- Diarrheal diseases
- Diabetes mellitus
- Kidney diseases
What Changed?
A century ago, infectious diseases were the primary killers, resulting in low life expectancy. Over the last 100 years, thanks to antibiotics, vaccines, and sanitation, we’ve largely conquered these threats. Life expectancy has gone up.
But in their place, new enemies have emerged—Lifestyle Diseases, also known more technically as Metabolic Diseases. This blog is a simple attempt to understand them, written by a layman, for laymen.
Our Two Energy Systems: Aerobic vs Anaerobic Respiration
Respiration is the process by which our bodies break down food to release energy. There are two primary types:
| Feature | Aerobic Respiration | Anaerobic Respiration |
|---|---|---|
| Oxygen use | Yes | No |
| Energy yield | High | Low |
| Speed | Slow | Fast |
| Duration sustainable | Long | Short |
| Example use case | Daily activity, fat burning | Sprinting, heavy lifting |
How We Evolved: Scarcity as a Teacher
Our ancestors lived in an environment of scarcity. Food was hunted or gathered occasionally, not constantly available. As a result, the body’s default energy system was aerobic respiration. We would burn fat slowly and efficiently, using oxygen.
When a sudden burst of energy was needed—to escape a predator or haul a kill back to camp—the anaerobic system would kick in. This provided quick energy but was inefficient and short-lived. Afterward, rest would follow, and the body would return to aerobic mode.
Modern Life: Constant Abundance, Constant Strain
Today, the environment has flipped. Food is available 24/7. Many of us eat 5 times a day, often calorie-rich but nutrient-poor meals. This persistent flood of glucose leads to the body defaulting to anaerobic respiration.
Our cells, overwhelmed and underutilized in terms of oxygen, begin to operate inefficiently. Over time, this imbalance contributes to many chronic illnesses.
We’ve shifted from being fat-adapted to carb-adapted!
Reclaiming the Natural Order: From Carb Back to Fat
This flip in our energy systems opens the door to metabolic disorders—including obesity, diabetes, and even cancer. But the solution, though not easy, is surprisingly simple.
Reclaiming Metabolic Health: Simple Steps
- Reduce excess carbohydrate intake, especially refined sugars.
- Eat nutrient-dense whole foods that nourish, not just fill.
- Restrict your eating window – consider eating just 1–2 meals a day.
- Practice intermittent fasting – eat only when you’re genuinely hungry.
- Stay physically active to engage your aerobic system.
These habits can help your body return to its natural rhythm—efficient, balanced, and evolutionarily sound.
The shift from infectious to metabolic diseases over the past century reflects both medical triumphs and new challenges. Your focus on metabolic health nails a core driver of today’s top killers—heart disease, stroke, diabetes, and beyond. By returning to ancestral patterns (less processed food, more movement, periodic fasting), we can mitigate these risks. The biology is clear, but the real hurdle is cultural and systemic change.
Written by a layman, for a layman—with a little help from history and biology.