Added sugar is one of the most significant contributors to the modern chronic disease epidemic.

Types of sugar:

• Glucose — primary cellular fuel, moderate insulin response
• Fructose — metabolized almost entirely in the liver. In excess, causes fatty liver, raises triglycerides, drives insulin resistance.
• Sucrose — table sugar = 50% glucose + 50% fructose
• High-fructose corn syrup (HFCS) — ~55% fructose. Found in processed foods, soda.

Recommended limits:

• WHO: Less than 10% of total calories from added sugar (ideally <5%)
• For a 2000-calorie diet: <50g/day (ideally <25g)
• A single 12oz Coke has 39g of sugar

Key insight: Sugar has no essential nutritional value. It provides calories with zero micronutrients.

Reference:

Wikipedia: Sugar

https://en.wikipedia.org/wiki/Sugar