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Background: Obesity is a serious public health concern worldwide, and nearly 40% of all adults in the United States and 21% in Sweden are now living with obesity. Efforts focusing mainly on weight loss have fallen short in reducing obesity prevalence. There is a great need for improved insight into what factors may promote a healthy weight, thereby avoiding the adverse health outcomes linked to obesity. Primary weight maintenance is a prevention strategy that emphasizes keeping a long-term stable weight in the non-obese range.

Aim: The overall aims of this thesis were to improve understanding of the patterns of obesity and obesity-related mortality among rural adults in Central New York State (U.S.) and Västerbotten County (Sweden), and to explore factors that are related to primary weight maintenance.

Material and methods: Data from U.S. health surveys and health examinations in Sweden were used to compare twenty-year (1989-2009) trends in body mass index (BMI) and obesity using multi-factor analysis of variance. The association between obesity and risk of 1) premature all-cause death, and 2) premature circulatory death, was compared between the U.S. and Sweden using proportional hazards regression. In 2009, a longitudinal questionnaire of attitudes, behaviors and perceptions regarding weight maintenance was administered to U.S. subjects. Associations between ten-year weight change and survey variables were tested using multiple linear regression, separately for sex and age strata. To gain a deeper understanding of influences, facilitators and barriers to healthy eating and physical activity, a qualitative interview study was conducted with U.S. women aged 26-35, with data analyzed by qualitative content analysis.

Results: Over twenty years, BMI increased for both men and women in all age strata in both countries, and those with no university education consistently had higher BMI than their university-educated counterparts. BMI increased more for younger groups (ages 36-45) compared to those aged 46-55 and 56-62. U.S. females aged 36-45 showed the greatest increases in average BMI, particularly when comparing 1999 to 2009. Increases in the prevalence of obesity (BMI≥30) in Sweden were more modest than in the U.S. Severe obesity (BMI≥35) was associated with significantly increased risk of premature death from all causes and from circulatory causes for all subjects. Severe obesity was less common in Sweden (2% of men, 3% of women) than in the U.S. (8% of men, 9% of women). Nonetheless, severely obese Swedish men had 2.9 times the risk of premature death from all causes compared to those of normal weight, and 4.9 times the risk for circulatory causes. The gradient of risk among U.S. men was significantly lower than in Sweden; those with severe obesity had a 1.6 times increased risk for all-cause premature death and 3.2 times increased risk for premature circulatory death. The pattern of risk among women did not differ between countries. Longitudinal analysis of U.S. health survey participants showed that women aged 26-35 gained the most weight of any group (mean=10.3kg gained over ten years). The variables found to be associated with ten-year weight change were different across sex and age groups. Among women, all variables associated with weight change were exercise-related. Among men, three of the four predictors were focused on eating habits. Interviews with women aged 26-35 revealed the challenges of healthy eating and engaging in physical activity. Women often identified as caregivers for others, and those with more social support, who were financially stable and showed self-efficacy around healthy choices were able to more consistently engage in healthy habits.

Conclusions: Obesity is an increasing problem for the rural adult population in both the U.S. and Sweden. When primary weight maintenance strategies are designed to support individuals towards healthy eating and increased physical activity, the complexity of the living environment must be considered. Individual conditions and personal relationships as well as the physical environment, home environment and work environment must be included in the assessment. Development of targeted programs for primary weight maintenance should be a focus of public health work for adults in rural areas in both Sweden and the U.S.