Flexible or Rigid Dieting: Which Yields Better Results?

eazy

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Alex has the muscle and the discipline. It’s time for his first bodybuilding competition—but he has no diet.

He hires a coach and gets a rigid plan: four ounces of white fish every night—tilapia only. Want a Red Delicious with peanut butter instead of a Honeycrisp with almond butter? Forget it.

A rigid diet is strict: a narrow list of foods, everything else forbidden.

Alternatively, Alex could follow a flexible diet (IIFYM). Hit your calorie and macro targets, and you can enjoy more variety—even an occasional treat.

The Study

23 lifters followed either a rigid or flexible diet for 10 weeks. Calories were cut 20%, protein was 0.9g per pound of body weight, and workouts stayed the same.
Results: Both groups lost about six pounds of fat. The rigid group was slightly ahead—but not enough to matter.

The Takeaway

Rigid or flexible—both work if calories are in check and protein is high.
  • Rigid diets: perfect for rule-followers who like strict structure.

  • Flexible diets: more variety, still requires tracking, but makes adherence easier for some.

Protein Is King
The real critical factor? Protein. High protein preserves muscle, supports fat loss, and keeps you full. Aim for 0.9–1.3g per pound of body weight. Focus here, and the rest—rigid or flexible—just fine-tunes the process.


Conlin, et al. "Flexible vs. rigid dieting in resistance-trained individuals seeking to optimize their physiques: A randomized controlled trial." J Int Soc Sports Nutr. 2021 Jun 29;18(1):52. doi: 10.1186/s12970-021-00452-2.

Which method do you prefer?
 

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