Calories vs. Hormones: Both Matter
The Debate
Low-carb gurus claim calories don’t matter: only insulin does. Cut carbs to zero, eat unlimited fat, and watch the weight fall off.
It’s more complicated than that.
What The Evidence Says
Weight loss requires a caloric deficit. Period.
- Controlled ward studies: When calories match, low-carb and low-fat produce identical fat loss (Hall et al., 2021).
- DIETFITS trial (n=609): No difference in 12-month weight loss between approaches (Gardner et al., 2018).
- Why low-carb “works”: It suppresses appetite, so people eat less without tracking. Behavioral effect, not metabolic magic.
You can’t escape thermodynamics. But hormones affect how hard it is to maintain a deficit.
The 80/20
- Cut processed carbs : Better satiety, stable energy
- Prioritize protein : Preserves muscle, kills hunger
- Don’t ignore quantity : Calories still drive the scale (American Heart Association, 2021)
The best diet is one you’ll actually follow. For most people, that means whole foods, adequate protein, and not obsessing over either extreme.
Definition
The calories vs. hormones debate asks whether weight management is purely about energy balance (calories in vs. calories out) or whether hormonal responses to food — particularly insulin — are the primary driver. The evidence supports a nuanced answer: calories determine weight change, but hormones influence how easy or hard it is to maintain a deficit. Both matter; neither is the whole story.
When This Applies
- Choosing a diet approach: Understand that any effective diet works through calorie reduction, even if the mechanism is appetite suppression
- Evaluating diet claims: When someone says “calories don’t matter,” they’re wrong. When someone says “just eat less,” they’re oversimplifying
- Troubleshooting a plateau: If weight loss stalls, check both quantity (calories) and quality (food choices that affect satiety and hormones)
- Deciding between low-carb and low-fat: Neither is inherently superior; pick whichever you’ll sustain
Related
- Protocol: Eat Well (put this knowledge into practice)
- Concept: Nutritional Density (food quality matters more than macro ratios)
- Concept: Saturated Fat and LDL (managing lipids alongside weight)
- Anti-Patterns: Health Anti-Patterns (extreme diet hopping)