DEVELOPMENT, IMPLEMENTATION, AND EVALUATION OF A WEIGHT-MANAGEMENT PROGRAM BASED ON THE 2005 DIETARY GUIDELINES FOR AMERICANS
Open Access
- Author:
- Psota, Tricia Lynn
- Graduate Program:
- Nutrition
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 10, 2009
- Committee Members:
- Penny Margaret Kris Etherton, Dissertation Advisor/Co-Advisor
Penny Margaret Kris Etherton, Committee Chair/Co-Chair
Barbara Ann Lohse, Committee Member
Barbara Jean Rolls, Committee Member
Sheila Grace West, Committee Member
Linda Ann Wray, Committee Member - Keywords:
- lifestyle modification
physical activity
diet
2005 Dietary Guidelines for Americans
weight management
Obesity/overweight
nutrition education
chronic disease risk
eating behavior - Abstract:
- Our national guidelines for diet and physical activity are the Dietary Guidelines for Americans; yet, their effectiveness for weight-management has not been determined. In addition, research indicates that diets consistent with the Dietary Guidelines improve chronic disease risk factors and are effective for weight loss; yet, few Americans follow these dietary recommendations. Therefore, the Weight Optimization: Revamping Lifestyles using the Dietary Guidelines (WORLD) study evaluated the effects of an intensive, theory-based, nutrition education program for weight management and guided by the 2005 Dietary Guidelines for Americans on clinical, biochemical, and dietary outcomes. The education program, Your Healthy World, was based on the social cognitive theory and delivered using problem-based learning, a format untested in a long-term nutrition education program for consumers. Your Healthy World was tailored for the lower end (20% kcal from fat; lower-fat diet) or upper end (35% kcal from fat; moderate-fat diet) of the Dietary Guidelines recommended range of fat intake. Pre-menopausal, overweight/obese women (n=101; BMI: 25-39.9 kg/m2; LDL-cholesterol: 100-189 mg/dL; aged 21-50 years) were randomized to either a lower-fat or moderate-fat diet in a parallel-arm design. The intervention consisted of 28 education sessions and twice weekly supervised aerobic exercise sessions over the course of one year. Intention-to-treat analyses (n=101) show that after one year weight loss was similar between the lower-fat and moderate-fat treatment groups (-5.0 and -4.3 kg; P¡¯s < 0.0001 compared to baseline). Overall, total cholesterol and LDL-cholesterol concentrations decreased (-0.09 and -0.10 mmol/l, respectively; P¡¯s < 0.05) and HDL-cholesterol concentration increased (+0.05 mmol/l; P < 0.05). Since energy and nutrient intakes, specifically total fat intake, did not differ between treatment groups participants were reclassified according to actual fat intake. If average fat intake from months 4 and 12 contributed less than 27.5% of total energy participants were classified as consuming a lower-fat diet; participants consuming a diet in which average fat intake from months 4 and 12 contributed more than 27.5% of total energy were considered moderate-fat consumers. The cutpoint of 27.5% of energy was used since it is the midpoint of the Dietary Guidelines recommendation for dietary fat (i.e., 20-35% of energy from fat). After reclassifying participants, total, LDL, and HDL-cholesterol concentrations were lower and triglyceride concentrations higher in participants reporting consumption of a lower-fat diet compared to participants consuming a moderate-fat diet (P¡¯s ¡Ü 0.05). The strongest predictors of weight loss were changes in aerobic capacity, binge-eating behaviors, baseline body weight and changes in trans fat intake, which together accounted for 20% of the variance in 12-month weight loss. An increase in aerobic capacity, a decrease in trans fat intake, and higher baseline binge-eating behaviors and body weight were associated with greater weight loss. When evaluating the effects of the intervention on diet-related variables in participants providing data at month 12 (n=60), the Healthy Eating Index-2005 (HEI-2005), a tool to assess adherence to the Dietary Guidelines, was used. The HEI-2005 consists of twelve components (i.e., total fruit; whole fruit; total vegetables; dark green and orange vegetables and legumes; total grains; whole grains; milk; and meat and beans; oils; saturated fat; sodium; and calories from solid fats, alcohol, and added sugars). For most components, higher intakes result in higher scores; however, the saturated fat, sodium, and calories from solid fats, alcoholic beverages, and added sugars components, lower intake levels result in higher scores because lower intakes are more desirable. A time effect was seen for increases in total fruit, whole fruit, whole grains, meat and beans, and saturated fat component scores, as well as summary scores, of the HEI-2005 (P < 0.01 for all). Total HEI-2005 scores were not different between participants consuming a lower-fat diet or a moderate-fat diet (80.58 ¡À 1.95 and 74.69 ¡À 1.33, respectively; P = 0.13). Component scores for total vegetables, dark green and orange vegetables and legumes, and whole grains, and total HEI-2005 score increased across tertiles as energy density of the diet decreased (P < 0.01 for all). The strongest predictors of energy density were baseline energy density and changes in scores for the total fruit component, the oils component, and total HEI-2005, which together accounted for 56% of the variance in dietary energy density at month 12. The strongest dietary predictors of weight loss were increases in the total vegetables component score, the oils component score, trans fat intake, the total grains component score, and baseline body weight, which together accounted for 15% of the variance in weight loss at month 12. Results of the WORLD study demonstrate that lower-fat and moderate-fat diets consistent with the Dietary Guidelines are equally effective for weight management. In particular, study participants were able to maintain weight loss during the maintenance period and did not experience the rebound in body weight often seen in other studies. In support of the Dietary Guidelines recommendations for physical activity, aerobic fitness was the main predictor of weight loss in this study. In addition, findings from this study indicate that women can follow the dietary recommendations of the Dietary Guidelines for weight loss and maintenance and improve diet quality as assessed by the HEI-2005. Results from this study support using the Dietary Guidelines for health promotion and chronic disease risk reduction during weight loss and maintenance of a reduced body weight.