Most health advice circulating online is outdated or flat-out wrong. Here are three that keep coming up:

1. "You need 8 glasses of water a day"

There's no solid study behind this. Hydration needs vary massively by body weight, activity, and climate. A better signal: the color of your urine.

2. "Breakfast is the most important meal of the day"

This was popularized by cereal companies in the early 1900s — not nutritionists. Intermittent fasting research suggests skipping breakfast can actually improve insulin sensitivity for many people.

3. "High-fat diets cause heart disease"

The original Ancel Keys study that launched the low-fat movement cherry-picked data from 7 countries while ignoring 15 others that contradicted his hypothesis. Modern meta-analyses paint a very different picture.

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