How a 50-Year-Old Study About Milkshakes Duped Psychology

March 13, 2026 - 19:04

A foundational psychological study from over fifty years ago, involving milkshakes and perceptions of fullness, is now under scrutiny for potentially misleading our understanding of dieting and eating disorders for decades. The research, long cited in textbooks, suggested that chronic dieters could become insensitive to their body's natural hunger cues.

The experiment involved giving participants either a rich milkshake or a bland shake-like drink, followed by a taste test of various crackers. The original conclusion was that restrictive dieters, after the milkshake, lost the ability to judge their fullness and ate more crackers, unlike non-dieters. This framed dieters as having a broken psychological relationship with food.

Modern analysis, however, points to critical flaws in the study's design and interpretation. The sample size was exceptionally small, and the data showed high variability, making strong conclusions statistically unreliable. Furthermore, the original interpretation may have pathologized normal eating behavior and inadvertently contributed to a cycle of blame and shame around dieting.

Experts now argue this study exemplifies how oversimplified science can shape harmful cultural narratives. It promoted the idea that willpower failure, rather than complex biological and psychological factors, is central to diet struggles. This revelation underscores the need to re-evaluate long-held assumptions, suggesting the link between restrictive dieting and disordered eating is far more nuanced than a single flawed experiment led us to believe.