Researchers compared a “flexible” vs. “rigid” approach to dieting. While rigid meal plans might make it easier to start a successful diet in the short term, investing the time and energy to learn how to track your macros (‘flexible dieting’) could pay off in the long run.


This study compared a “rigid” (no substitutions allowed, meal plan-based) diet to a “flexible” (macronutrient target-based) diet.

23 participants (13 women, 10 men) underwent a 10-week dieting phase matched for energy and macronutrients.

The “flexible” group was taught to track their macros, make food substitutions, and hit specific macronutrient targets on a day-to-day basis.

The “rigid” group was given a few set meal plans to follow daily without substitutions.

After the diet phase the participants were observed for a post-diet phase, with resting metabolic rate, eating behavior, and body composition measurements occurring during both phases.


  1. There were no significant differences between groups after the diet phase for any variable.
  2. However, after the post-diet phase the rigid group significantly increased their fat mass, while the flexible group did not.
  3. The flexible group also gained significantly more fat-free mass than the rigid group.   

Key Takeaways

  1. Higher adherence in the rigid group might be due to easier adoption of the meal plan-based diet, compared to the flexible group who had to learn to track, make food substitutions, and hit macro targets.
  2. Better body composition changes in the flexible group after the 10-week post-diet phase might have occurred because they retained the nutritional knowledge and skills they learned during the diet. 
  3. It’s possible that the rigid approach was easier to follow initially than the flexible approach, but the flexible approach resulted in better adoption of nutritional skills, knowledge, and habits that supported body composition improvements in the long run.