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.
American Heart Association. (2021). 2021 Dietary Guidance to Improve Cardiovascular Health. Circulation.
Gardner, C. D., Trepanowski, J. F., Del Gobbo, L. C., Hauser, M. E., Rigdon, J., Ioannidis, J. P. A., Desai, M., & King, A. C. (2018). Effect of Low-Fat vs Low-Carbohydrate Diet on 12-Month Weight Loss in Overweight Adults and the Association With Genotype Pattern or Insulin Secretion: The DIETFITS Randomized Clinical Trial. JAMA, 319(7), 667–679. https://doi.org/10.1001/jama.2018.0245
Hall, K. D., Guo, J., Courville, A. B., Boring, J., Brychta, R., Chen, K. Y., Darcey, V., Forde, C. G., Gharib, A. M., Gallagher, I., Howard, R., Joseph, P. V., Milley, L., Ber, R., Rickman, M., Stephens, S., Summers, S., Walter, M., Walter, P. J., … Chung, S. T. (2021). Effect of a plant-based, low-fat diet versus an animal-based, ketogenic diet on ad libitum energy intake. Nature Medicine, 27, 344–353. https://doi.org/10.1038/s41591-020-01209-1