Carbohydrate intake and overweight and obesity among healthy adults.

Background: Little is known about the dietary habits of people with optimal body weight in communities with high overweight and obesity prevalence.
Objective: To evaluate carbohydrate intake in relation to overweight and obesity in healthy, free-living adults.
Design: We used a cross-sectional analysis.
Subjects/setting: The Canadian Community Health Survey Cycle 2.2 is a cross-sectional survey of Canadians conducted in 2004-2005. There were 4,451 participants aged 18 years and older with anthropometric and dietary data and no comorbid conditions in this analysis.
Main Outcome Measures: Outcome variables were body mass index (BMI; calculated as kg/m(2)) and overweight or obesity status (dichotomous) defined as BMI > or =25 compared with BMI <25 based on measured height and weight. Diet was evaluated by 24-hour dietary recall based on the Automated Multi-Pass Method.
Statistical Analyses Performed: Weighted regression models with bootstrapping and cubic splines were used. Outcome variables were BMI and overweight or obesity, and predictors were daily nutrient intake. Adjustment for total energy intake, age, leisure time energy expenditure, sex, smoking, education, and income adequacy was performed.
Results: Risk of overweight and obesity was decreased in all quartiles of carbohydrate intake compared to the lowest intake category (multivariate odds ratio quartile 2=0.63; 95% confidence interval: 0.49 to 0.90; odds ratio quartile 3=0.58; 95% confidence interval: 0.41 to 0.82; odds ratio quartile 4=0.60; 95% confidence interval: 0.42 to 0.85). Spline analyses revealed lowest risk among those consuming 290 to 310 g/day carbohydrates.
Conclusions: Consuming a low-carbohydrate (approximately <47% energy) diet is associated with greater likelihood of being overweight or obese among healthy, free-living adults. Lowest risk may be obtained by consuming 47% to 64% energy from carbohydrates.