High Prevalence of Overweight and Obesity in Samoa
Recent and historical data consistently show that Samoan populations have some of the highest rates of overweight and obesity in the world. According to data from the World Health Organization and other studies, the prevalence of overweight (BMI > 25) and obesity (BMI > 30) is alarmingly high, affecting the vast majority of the adult population. While there are regional differences between independent Samoa and American Samoa, the overall trend is clear. A 1995 survey cited in an American Samoa Community Cancer Coalition report noted a mean BMI of 33.7 for men and 36.2 for women, with 74.6% of adults in the 25-64 age group classified as obese. In contrast, a 2018 study in independent Samoa found average adult BMI had risen significantly since 1995, reaching 38.57 for women and 33.78 for men. Less than 10% of adult women in Samoa can maintain a normal weight.
The Genetic Factor: The CREBRF Variant
Genetics play a role in the high BMI observed in Samoans, though it is not the sole cause. A landmark 2016 study published in Nature Genetics identified a 'thrifty' gene variant in the CREBRF gene on chromosome 5 that is common among Samoans but virtually nonexistent in other populations. This missense mutation was found in about half the Samoan population tested, increasing an individual's BMI by 1.36-1.45 kg/m2 per copy of the variant. The variant effectively increases fat storage efficiency and decreases cellular energy metabolism, likely an evolutionary advantage for ancestors who endured periods of food scarcity and long ocean voyages.
Key takeaways from the genetic findings:
- The CREBRF variant increases the risk of obesity more than any other known common BMI-risk variant.
- However, the variant explains only about 2% of the total variation in BMI among Samoans, meaning other factors are far more influential.
- Researchers stress that having the gene is not an inevitable fate for obesity and that lifestyle factors remain paramount.
Environmental and Cultural Drivers of Increased BMI
While genetics provide a piece of the puzzle, the rapid and recent rise in obesity rates over the past few decades points to significant environmental and cultural shifts as the primary drivers.
The Dietary Shift: From Traditional to Imported Foods
Historically, the Samoan diet consisted of fresh, locally sourced foods like fish, seafood, taro, breadfruit, and coconuts. Over the past half-century, modernization has led to a major dietary transition towards imported, processed foods that are high in calories, sugar, salt, and unhealthy fats. Cheaper, non-perishable imported goods like canned tuna, corned beef, Spam, and heavily sweetened beverages have replaced traditional staples. This shift dramatically increases daily caloric intake while decreasing nutritional value, a pattern common in many Pacific Island nations.
Sedentary Lifestyles and Urbanization
Parallel to the dietary changes, a shift in lifestyle has occurred. Traditional life involved active, physically demanding work on plantations, fishing, and clearing land. Modern life, with more sedentary jobs and greater reliance on technology and motor vehicles, has drastically reduced daily physical activity. This energy imbalance, where people consume more calories than they expend, fuels the obesity epidemic.
Cultural Perceptions of Body Size
Samoan culture has traditionally associated larger body sizes with social status, health, and beauty, a perception rooted in times when abundance was a sign of prosperity. While this perspective is shifting, it has historically meant less social pressure to maintain a leaner body type. A 2018 study found that while preferences for ideal body size have increased along with average size, there is also a growing awareness of health risks, though this hasn't always translated to behavioral changes. The conflict between changing health risks and enduring cultural norms complicates public health messaging.
Comparison of Factors Contributing to High BMI
| Factor | Influence on Samoan BMI | Influence on General Population BMI (Western Countries) |
|---|---|---|
| Genetics | A specific, impactful 'thrifty' variant in the CREBRF gene is common and increases fat storage, though it explains a small portion of the overall variation. | Multiple genetic variants contribute, but none with the same pronounced, population-specific effect as the CREBRF variant in Samoans. |
| Diet | Rapid shift from traditional, low-sugar, complex carbohydrate diet to cheap, imported, high-calorie processed foods like canned meat, refined starches, and sugary drinks. | Dietary changes toward processed foods are also a major factor, but the shift from pre-industrial diets was less abrupt and extreme. |
| Lifestyle | Rapid urbanization and shift away from physically demanding traditional activities to sedentary work and leisure. | Modern lifestyles are also generally sedentary, but the contrast with historical activity levels is less dramatic for many. |
| Cultural Norms | Historical appreciation for larger body size as a sign of wealth and health, though perceptions are changing. | Societal norms often emphasize slimness, leading to different forms of social pressure regarding body weight. |
Public Health Challenges and Responses
The high prevalence of obesity among Samoans has led to corresponding high rates of non-communicable diseases (NCDs), including type 2 diabetes, hypertension, and cardiovascular disease. Public health efforts have been ongoing for decades, primarily focusing on behavior change strategies like diet and exercise advice. However, these initiatives have seen limited success due to complex underlying issues such as poverty, the low cost of processed imports, and structural factors that are difficult to overcome with individual-focused messaging alone. A shift toward multi-sectoral policies that address trade, agriculture, and urban planning is recognized as necessary for sustained improvement.
Conclusion
The question of what is the BMI of Samoans reveals a multifaceted public health crisis. While a unique genetic variant contributes to a higher predisposition for fat storage, the dramatic increase in average BMI over recent decades is overwhelmingly driven by environmental and cultural shifts. The transition from traditional, active lifestyles and locally sourced diets to sedentary habits and cheap, imported processed foods has created an 'obesogenic' environment. Addressing this challenge requires a comprehensive, multi-sectoral approach that moves beyond simple health advice to tackle the deeper economic, trade, and social factors at play. Recognition of the complex interplay of genetics, environment, and culture is essential for developing effective, culturally appropriate interventions that can reverse the alarming health trends in Samoa. Find more detailed information on the genetic aspect of Samoan obesity by visiting the Brown University news release describing the discovery of the CREBRF gene variant.
