Researchers Explore Reasons Behind Extreme Thinness in Individuals

A growing body of research is investigating why some individuals struggle to gain weight, despite consuming adequate calories. Approximately 1.9 percent of the global population is classified as “constitutionally thin,” with around 6.5 million affected individuals in the United States alone. These individuals often experience significant distress over their weight, leading to a renewed focus on understanding the metabolic and genetic factors that contribute to their condition.

Many individuals seeking guidance on weight gain approach coaches like Bella Barnes, who specializes in helping those who feel too thin. Barnes has encountered clients who resort to wearing padded clothing to appear larger, highlighting the societal pressures faced by this demographic. While the spotlight often shines on the growing number of people classified as obese, constitutionally thin individuals remain largely overlooked, facing their own set of challenges and stigmas.

Scientific Insights into Constitutional Thinness

Researchers are delving into the unique metabolic processes that characterize constitutionally thin individuals. In a recent paper published in the Annual Review of Nutrition, authors describe this condition as a “real enigma” that challenges established beliefs about energy balance and metabolism. Despite consuming calories similar to their peers, many constitutionally thin people maintain a body mass index (BMI) below 18.5, and in some cases, as low as 14, translating to a weight of just 72 pounds for someone who is five feet tall.

Recent studies indicate that genetic and metabolic factors play a significant role in this phenomenon. A landmark experiment conducted in 1990 involving identical twins revealed considerable variability in weight gain, even when both were subjected to the same caloric surplus. Some participants gained nearly 30 pounds, while others gained less than 10 pounds, suggesting a strong genetic component influencing weight regulation.

Research has shown that constitutionally thin individuals tend to resist weight gain, particularly when consuming high-fat foods. They may gain weight during periods of overfeeding, but this weight often dissipates quickly once they return to normal eating habits. This observation aligns with the idea that many individuals have a preprogrammed weight “set point” that their bodies strive to maintain.

Challenges and Stigmas Faced by the Thin

Like their overweight counterparts, constitutionally thin individuals often face social stigma. Comments about their appearance can lead to feelings of inadequacy and discomfort. Jens Lund, a postdoctoral researcher at the Novo Nordisk Foundation Center for Basic Metabolic Research, notes that thin individuals may feel scrutinized in social settings, fearing that others might misinterpret their eating habits as indicative of an eating disorder. This stigma reinforces the need for greater awareness and understanding of the challenges faced by those struggling with extreme thinness.

Researchers are now investigating the metabolic differences that may explain why some individuals remain thin despite consuming excess calories. A recent meta-analysis revealed that constitutionally thin individuals have nearly normal fat levels but exhibit significantly lower muscle mass compared to their peers. This reduced muscle mass could lead to health complications, including an increased risk of osteoporosis in older age, particularly among women.

Ongoing research is also focusing on the calorie expenditure of constitutionally thin individuals. Some studies suggest that they may engage in more fidgeting or have higher rates of caloric excretion than heavier individuals. Understanding these metabolic quirks could pave the way for new treatments not only for those struggling to gain weight but also for individuals with obesity.

As research progresses, Lund and his colleagues aim to launch a comprehensive study at the University of Copenhagen, utilizing a metabolic chamber to track energy intake and expenditure in constitutionally thin individuals. This study could yield valuable insights into the underlying mechanisms of constitutional thinness.

In conclusion, while the societal focus often centers on obesity and weight loss, a significant number of people grapple with the opposite issue. As scientists delve deeper into the biological and genetic underpinnings of extreme thinness, there is hope for greater understanding and support for those affected by this condition.