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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.

BACKGROUND: Understanding the impact of obesity on premature mortality is critical, as obesity has become a global health issue.

OBJECTIVE: To contrast the relationship between body mass index (BMI) and premature death (all-cause; circulatory causes) in New York State (USA) and Northern Sweden.

METHODS: Baseline data were obtained between 1989 and 1999 via questionnaires (USA) and health exams (Sweden), with mortality data from health departments, public sources (USA) and the Swedish Death Register. Premature death was death before life expectancy based on sex and year of birth. Within country and sex, time to premature death was compared across BMI groups (18.5-24.9 kg/m² (reference), 25-29.9 kg/m², 30.0-34.9 kg/m², ≥35.0 kg/m²) using Proportional Hazards regression. Absolute risk (deaths/100,000 person-years) was compared for the same stratifications among nonsmokers.

RESULTS: 60,600 Swedish (47.8% male) and 31,198 US subjects (47.7% male) were included. Swedish males with BMI≥30 had increased hazards (HR) of all-cause premature death relative to BMI 18.5-24.9 (BMI 30-34.9, HR = 1.71 (95% CI: 1.44, 2.02); BMI≥35, HR = 2.89 (2.16, 3.88)). BMI≥25 had increased hazards of premature circulatory death (BMI 25-29.9, HR = 1.66 (1.32, 2.08); BMI 30-34.9, HR = 3.02 (2.26, 4.03); BMI≥35, HR = 4.91 (3.05, 7.90)). Among US males, only BMI≥35 had increased hazards of all-cause death (HR = 1.63 (1.25, 2.14)), while BMI 30-34.9 (HR = 1.83 (1.20, 2.79)) and BMI≥35 (HR = 3.18 (1.96, 5.15)) had increased hazards for circulatory death. Swedish females showed elevated hazards with BMI≥30 for all-cause (BMI 30-34.9, HR = 1.42 (1.18, 1.71) and BMI≥35, HR = 1.61 (1.21, 2.15) and with BMI≥35 (HR = 3.11 (1.72, 5.63)) for circulatory death. For US women, increased hazards were observed among BMI≥35 (HR = 2.10 (1.60, 2.76) for all-cause and circulatory HR = 3.04 (1.75, 5.30)). Swedish males with BMI≥35 had the highest absolute risk of premature death (762/100,000 person-years).

CONCLUSIONS: This study demonstrates a markedly increased risk of premature death associated with increasing BMI among Swedish males, a pattern not duplicated among females.

OBJECTIVES: To contrast the validity of two modes of self-reported height and weight data.

DESIGN: Subjects' self-reported height and weight by mailed survey without expectation of subsequent measurement. Subjects were later offered a physical exam, where they self-reported their height and weight again, just prior to measurement. Regression equations to predict actual from self-reported body mass index (BMI) were fitted for both sets of self-reported values. Residual analyses assessed bias resulting from application of each regression equation to the alternative mode of self-report. Analyses were stratified by gender.

SETTING: Upstate New York.

PARTICIPANTS: Subjects (n = 260) with survey, pre-exam and measured BMI.

MAIN OUTCOME MEASURES: Prevalence of obesity based on two modes of self-report and also measured values. Bias resulting from misapplication of correction equations.

RESULTS: Accurate prediction of measured BMI was possible for both self-report modes for men (R (2 )= 0.89 survey, 0.85 pre-exam) and women (R (2 )= 0.92 survey, 0.97 pre-exam). Underreporting of BMI was greater for survey than pre-exam but only significantly so in women. Obesity prevalence was significantly underestimated by 10.9% (p < 0.001) and 14.9% (p < 0.001) for men and 5.4% (p = 0.007) and 11.2% (p < 0.001) for women, for pre-exam and survey, respectively. Residual analyses showed that significant bias results when a regression model derived from one mode of self-report is used to correct BMI values estimated from the alternative mode.

CONCLUSIONS: Both modes significantly underestimated obesity prevalence. Underestimation of actual BMI is greater for survey than pre-exam self-report for both genders, indicating that equations adjusting for self-report bias must be matched to the self-report mode.

BACKGROUND: Previous studies have focused on weight maintenance following weight loss, i.e. secondary weight maintenance (SWM). The long-term results of SWM have been rather modest and it has been suggested that preventing initial weight gain, i.e. primary weight maintenance (PWM), may be more successful. Therefore, developing a prevention strategy focused on PWM, enabling normal weight or overweight individuals to maintain their weight, would be of great interest. The aim of this study was to identify attitudes, strategies, and behaviors that are predictive of PWM in different age, sex and BMI groups in Northern Sweden. METHODS: A questionnaire was mailed to 3497 individuals in a Swedish population that had two measured weights taken ten years apart, as participants in the Västerbotten Intervention Programme. Subjects were between 41-63 years of age at the time of the survey, had a baseline BMI of 20-30, and a ten year percent change in BMI greater than -3%. The respondents were divided into twelve subgroups based on baseline age (30, 40 and 50), sex and BMI (normal weight and overweight). Analysis of variance (ANOVA), correlation, and linear regression were performed to identify independent predictors of PWM. RESULTS: Of the 166 predictors tested, 152 (91.6%) were predictive of PWM in at least one subgroup. However, only 7 of these 152 variables (4.6%) were significant in 6 subgroups or more. The number of significant predictors of PWM was higher for male (35.8) than female (27.5) subgroups (p=0.044). There was a tendency (non significant) for normal weight subgroups to have a higher number of predictors (35.3) than overweight subgroups (28.0). Adjusted R-squared values ranged from 0.1 to 0.420. CONCLUSIONS: The large number of PWM predictors identified, and accompanying high R-squared values, provide a promising first step towards the development of PWM interventions. The large disparity in the pattern of significant variables between subgroups suggests that these interventions should be tailored to the person's demographic (age, sex and BMI). The next steps should be directed towards evaluation of these predictors for causal potential.