Vanuatu, like many developing countries (6
), is experiencing a rapid increase in obesity with modernization. This is most evident in more economically developed regions such as suburban Efate. However, obesity represents an increasing concern for rural residents, especially in areas experiencing rapid cultural change such as Aneityum (rural with tourism). Prevalence of central obesity is particularly high among women, even in rural Ambae, where we might expect that largely traditional diets and lifestyles would result in low prevalence but where more than one-third of women have central obesity. These figures highlight the importance of assessing multiple indices of obesity in the population (20
). Estimates based on total body fat or abdominal fat could indicate increased risk in rural areas that might not be evident in analyses of BMI alone.
Our results suggest that increased animal protein intake is one behavioral contributor to increased obesity risk. The pattern of increased meat intake with economic development has been observed around the globe (4
). This often includes a heavier reliance on processed foods, such as tinned fish in our survey, which contributes independently to measures of obesity. We might expect similar risks associated with tinned meat intake, but tinned meat is more expensive and was thus consumed by relatively few participants in our survey (12
Both the nutrient content and the preparation methods of tinned fish likely contribute to its association with obesity. Tinned fish canned in oil or sauce has higher fat content than most types of fresh fish (21
). Furthermore, based on our observations, tinned fish and meat are often served with instant noodles and rice, whereas fresh fish and meat more often accompany dishes made with traditional root crops and vegetables, which are less calorie-dense by comparison. A heavy reliance on tinned fish in urban areas was noted during the first known nutrition survey conducted in Vanuatu in 1951 (22
), and has been observed in many areas of the Pacific (23
Our findings are similar to those of the Vanuatu Ministry of Health 1998 NCD survey, which highlighted associations among obesity and daily consumption of nontraditional fat sources (OR=2.19), including oil, margarine/butter, milk, fresh meat, poultry, tinned meat, and tinned fish (11
). However, our analyses suggest that tinned fish might contribute more to the risk of nontraditional fats compared to fresh meat (including poultry). In fact, including fresh meat in the nontraditional fats category might actually weaken the observed association, since this emerged as a protective factor in linear regression models, perhaps because fresh meat displaces other less healthy options in the diet. While fresh fish remains a major part of the diet in Vanuatu, it is not available in all areas and only seasonally in others. In this case, fresh meat might be a better dietary option than tinned fish.
Refined carbohydrates might also contribute to increased obesity risk. Packaged “2-minute” noodles are popular in Vanuatu and were associated with increased risk of obesity based on %BF among the whole sample, and with overweight/obesity based on BMI and obesity based on %BF among men. Nutrition education is not widespread in Vanuatu, so it is not commonly known how energy-dense and nutrient-poor these products are. They are chosen largely for their convenience (24
). Malcolm noted in 1952 that most people had little knowledge of the nutritional value of different classes of foods and recommended prioritizing nutrition education (22
). Those recommendations remain equally relevant today (26
Associations with physical activity variables were less robust in our analyses. Whereas we expected that spending more hours in sedentary recreation would be associated with increased risk, this actually emerged as a protective factor. We suspected that this might reflect higher levels of education among participants who spent more time in these forms of sedentary recreation: years of education was positively correlated with hours of TV/video/radio per week among both men and women [correlation 0.227 (p<0.001) and 0.181 (p=0.007), respectively], and these correlations remained significant even when controlling for age. However, years of education was not a significant predictor in any of our linear or logistic analyses. Nevertheless, participants who spend more time listening to TV and radio might receive more informal health education in the form of public health messages or popular opinions.
The 1998 Vanuatu NCD survey (11
) included a physical activity score based on frequency (0=Never, 1=Weekly, 2=Daily) of gardening, sports, and walking to work/garden, with a minimum score of 0 and a maximum score of 6. The only statistically significant differences were between individuals with light and moderate activity levels combined (score 0–4) compared to those with heavy activity (score 5–6) (OR=1.59). We calculated similar composite measures of physical activity, but none were reliably correlated with anthropometric indices or obesity risk.
Notably, the effects of physical activity and sedentary recreation on BMI appear to be most evident among individuals classified as obese (27
), and so might not be evident in our sample. Although obesity represents a growing concern on all the islands sampled, more than 60% of our participants had a BMI within the normal range and, depending on the criteria used, as few as 10% were classified as obese. Furthermore, physical activity levels were high among all participants in our sample, even those who spent the most time in sedentary recreation (12
). For example, most people walked for their daily errands and activities, with only 8.5% of men and 1.6% of women reporting taking a vehicle to work or gardens. Only 3.9% of men and 1.2% of women had jobs requiring little physical activity, and all but one participant maintained at least one (but usually multiple) traditional gardens, which was a protective factor in our analyses. Tending traditional gardens is labor intensive, and since gardens might be located up to few hours away from the household by foot, simply getting to the garden requires extended periods of physical activity. Finally, physically active recreation was popular on all islands. For example, 48.7% of men and 39.9% of women played sports on at least a weekly basis. In contrast, fewer participants spent extended periods of time in sedentary recreation. Daily hours of TV/radio/video averaged 1.69 hours for men and 0.85 hours for women, and only 27.2% of men and 11.7% of women watched more than 2 hours of TV per day. Sedentary behaviors and physical activity might each contribute uniquely to health outcomes (28
), and more analyses are thus necessary to identify the potential effects of sedentary behavior, and of subtle changes in physical activity levels, in this and similar highly active populations.
While our models for obesity correctly classify up to 90% of participants, other major contributors to obesity remain unaccounted for in our sample. Early growth patterns and genetic profile likely have a major impact on obesity risk in Vanuatu. For example, poor intrauterine growth followed by rapid catch-up growth contributes to increased risk of obesity later in life, and is a particularly important risk factor in developing countries (29
). Our analyses among adolescents showed higher than expected WHTR and central obesity prevalence among girls in Aneityum, and some evidence suggests that stunting in infancy might represent a contributing factor (31
). Furthermore, a number of genetic risk factors for chronic diseases have been identified in Pacific populations (32
), and this could account for much of the unexplained variance in anthropometric indices and obesity risk on all islands.
In areas experiencing rapid cultural change, obesity prevalence can increase in only a short period of time. Follow-up surveys conducted by our group in 2011 suggest that prevalence of obesity (defined by BMI) has increased since 2007 among both men and women in Efate (33
). This points to the importance of frequently monitoring population health and implementing prevention efforts early during transition, including in rural areas that might otherwise be overlooked due to relatively lower prevalence of obesity compared to urban areas.
In conclusion, our analyses suggest that relatively modest changes in behavior, diet in particular, can contribute markedly to increasing obesity prevalence during health transition. Despite the maintenance of traditional gardening among most residents, high levels of physical activity, and continued reliance on traditional foods, the incorporation of more animal protein and refined carbohydrates is large enough to contribute to increased risk of obesity in the archipelago. In light of the rapidity of weight gain observed during modernization, targeting rural areas where increasing tourism or other environmental factors lead to even modest changes in lifestyle represents an important public health focus. Where public health resources are limited, prioritizing messages about the risks of packaged and processed foods such as instant noodles, and heavy reliance on animal protein – especially more processed forms – could have a positive impact on population health. Early implementation of prevention measures coupled with continued monitoring of multiple measures of obesity could help countries in the early stages of health transition avoid the costly health burdens so prevalent in developed countries today.