American Council on Exercise by American Council on Exercise

Last Updated October 20, 2023 (originally published September 26, 2014) 

People come in a variety of shapes and sizes, so it might seem logical to assume that different eating plans and training routines would be more appropriate or impactful depending on one's body type. Unfortunately, this idea has given rise to numerous persistent misconceptions within the health and fitness industry. 

Conversations about somatotypes (the scientific term for human body types) often revolve around the concept that individuals can be neatly classified into three distinct body types—ectomorph, mesomorph and endomorph. The belief is that somatotyping can provide general guidelines on how a person should approach exercise, nutrition, lifestyle change and physical activity. However, the truth is that a person's somatotype characteristics can evolve over time, and many individuals embody a mix of all three somatotypes. 

To clarify, the three somatotypes—ectomorph, mesomorph and endomorph—have been described in scientific literature, but placing a person into a specific category is more complex than it seems. Transitioning from somatotyping to offering exercise recommendations and dietary advice often results in the spread of misinformation, contributing to the creation or proliferation of myths that become “common knowledge” over time. 

Here is a quick description of the three somatotypes: 

  • Ectomorph: Characterized by a slim body frame, small shoulders and hips, long arms and legs, and less muscle mass 

  • Mesomorph: Characterized by a medium build with higher-than-average muscular development, a low body-fat percentage, broad shoulders, and a muscular chest, shoulders and limbs. 

  • Endomorph: Characterized by a larger, rounder body shape, high levels of body fat, a propensity to gain weight, and shorter arms and legs. 

Common Myths about Endomorphs 

The following are some common myths that you may hear from clients or potential clients or read about in popular media. Your job is to sift through these types of statements and look for the evidence—which, in this case, you will not find.? 

  • Individuals with an endomorph body type cannot easily gain muscle. The truth is that you cannot tell how someone is going to respond to training simply by looking at their present shape and body composition.?? 

  • People with an endomorph body type (and the other body types) should eat certain foods while avoiding others. The best approach to nutrition is to find a healthy eating plan that the client can stick to over the long haul. There are no hard and fast rules. And, the negatively worded guidance to “avoid” a favorite or preferred food is not likely to lead to success.? 

  • A person with an endomorph body type will likely have less self-control than those with other body types. The idea that people with larger body types are lazy is a persistent, dangerous and damaging myth, especially if it taints the work of a health coach or exercise professional. It’s simply impossible to make judgments about a person’s work ethic, personality or readiness to change based on their appearance. 

  •  Endomorph body types represent people who are generally unhealthy. Yes, those with an endomorph body type by definition have higher levels of body fat, but that body fat can be lost through proper diet and exercise. Also, you cannot measure a person’s general health just by looking at them or by measuring their body composition. There are people with overweight or obesity who are metabolically healthy and do not have prediabetes or diabetes. Making assumptions about a persons health based on their body type is never a good idea. 

  • People with an endomorph body type are not suited for most athletic activities. There is a persistent myth, for example, that people with larger bodies cannot do yoga or Pilates, which may prevent them from trying different types of exercise they may love. Never lose sight of the fact that enjoyment of physical activity is a vital component of long-term adherence, so your role is to help clients uncover activities they might enjoy, not steer them away from options based on misconceptions. 


A Controversial Past  

The introduction of the three somatotype classifications can be traced back to the 1940s when Dr. W.H. Sheldon, a psychologist, brought them into the spotlight in his book, The Varieties of Human Physique. Dr. Sheldon aimed to categorize individuals based on how closely they aligned with the three body types, linking these types to traits such as temperament and even criminal tendencies. 

While Dr. Sheldon's work in constitutional psychology stirred controversy, its enduring impact on physical education and the fitness industry is undeniable. This method of categorization undermines the essence of personalized coaching and programming, which are fundamental aspects of effective health coaching and personal training. Relying solely on body types for decisions also opens the door to racial and cultural stereotypes. For instance, associating a particular race with higher endomorphy may lead to misguided assumptions about personality traits linked to body fat, perpetuating stereotypes like laziness, selfishness and a lack of self-control. 

This serves as a poignant example of implicit bias that health coaches and exercise professionals must actively recognize and address in their work. Unfortunately, individuals attribute personality traits to the three body types, fostering positive stereotypes for mesomorphs and ectomorphs while harboring negative stereotypes for endomorphs. 

Final Thoughts  

Somatotyping should not replace an individualized, client-centered approach to behavior change, as it provides no insight into how a person will respond to diet and exercise, let alone anything about their personality, temperament or self-control. A person's appearance alone should not dictate their macronutrient balance, the number of reps in a resistance-training set, or their overall goals. Instead, let each client's unique goals and values guide your programming and approach to behavior change and long-term adherence. As a health coach or exercise professional, your objective is to deliver a tailored plan for each client, and making assumptions without evidence will only hinder that process. 


Check out this course to explore how you can identify and address your implicit biases and strengthen your communication skills: Taking Action with ACE: Practicing Equity, Diversity and Inclusion as a Health and Fitness Professional?(worth 0.3 ACE CECs).

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