Traditional vs. Nontraditional Weight Loss Methods
Traditional vs. Nontraditional Weight Loss Methods
A cross-sectional analysis of the 2005–2010 National Health and Nutrition Examination Survey (NHANES) data was conducted. The NHANES is a continuous national survey that represents a stratified multistage probability sample of the noninstitutionalized US population. The NHANES combines questionnaires with physical examination findings and laboratory samples obtained from participants. The data are weighted to allow for computation of appropriate population estimates. This study was approved as exempt research by the Virtua Health institutional review board.
The subjects included in this study are nongeriatric (aged 20 to 65 years) adult participants in the 2005–2010 NHANES who answered "yes" to the question, "Have you tried to lose weight in the past year?" Female participants were excluded from analysis if they reported being pregnant at the time of the questionnaire or had given birth in the previous year. Participants who had a body mass index (BMI; weight in kilograms/height in square meters) in the underweight category (BMI <18.5) at the start of the weight loss year were also excluded. BMI at the start of the weight loss year was calculated from reported height at the time of survey and reported weight from 1 year before the survey. Other exclusions included participants with any missing demographic data or who did not identify at least one specific method they used to try to lose weight. There were 3367 participants who met inclusion and exclusion criteria, which represent 53,570,979 adults in the US population.
Patient Report of Weight. Participants were asked to report their weight at the time of survey administration as well as their weight 1 year before the survey. To evaluate for accuracy of self-assessed weight, a simple regression predicting measured weight from self-reported weight was performed and the R was examined.
Weight Loss Methods. Participants were asked whether they attempted to lose weight in the previous 12 months with a variety of methods. Because of the large number of possible methods, it was necessary for certain methods to be combined into broader categories. "Diet" methods included changed eating habits; ate less to lose weight; ate less fat to lose weight; ate fewer carbohydrates; ate less sugar, candy, or sweets; switched to foods with lower calories; ate more fruits, vegetables, or salads; ate diet foods or products; or followed a special diet. Participants were included in the "diet only" category if they only used one or more diet methods. Participants were included in the "exercise only" category if they reported only using exercise to lose weight. If a participant used any of the following methods, even in combination with diet and/or exercise methods, they were included in the "nontraditional methods" category: skipped meals, drank a lot of water, used a liquid diet formula, took prescription diet pills, took nonprescription diet pills, took laxatives or vomited, or started smoking cigarettes or began to smoke again. Those who used diet methods and reported exercising to lose weight, but did not use any of the nontraditional methods, were included in the "diet and exercise only" category. The weighted proportion of individuals using each technique was calculated.
Outcome Measures. The main outcome measure was the adjusted mean change in weight during the previous 12 months for individuals using each of the following weight loss method categories: diet only, exercise only, diet and exercise only, and nontraditional methods. Other outcome measures included the proportion of participants who lost weight using each method. The above measures were assessed in all of the participants and those whose self-report–based BMI at the beginning of the weight loss year placed them in the normal category (BMI 18.5–24.9), the overweight category (BMI 25.0–29.9), and the obese category (BMI ≥30.0).
Demographic characteristics of respondents included sex, age, ethnicity (non-Hispanic white, non-Hispanic black, Mexican American, and other), family income as indicated by poverty-to-income ratio (<1.0 indicates poverty), marital status (married/living with partner vs not married), and education level (high school graduate and higher vs less than a high school education).
Because the NHANES has a complex sampling design that makes the resulting sample representative of the noninstitutionalized US population, all of our results are expressed as nationally representative estimates. Analyses were performed using SUDAAN (version 11.0, RTI International, Research Triangle Park, NC) to account for the weighting and complex sampling design.
Unadjusted least square mean change in weight during the previous 12 months was calculated for each weight loss method and t tests were used to test for differences in means, using diet and exercise only as the reference group. The proportion of participants who lost weight during the previous 12 months was calculated for each weight loss method and χ tests were used to test for differences in proportions of successful weight loss. For all of the analyses, the weight loss method category of diet and exercise only was used as the reference category. Data analysis was performed in August 2013.
Methods
Design
A cross-sectional analysis of the 2005–2010 National Health and Nutrition Examination Survey (NHANES) data was conducted. The NHANES is a continuous national survey that represents a stratified multistage probability sample of the noninstitutionalized US population. The NHANES combines questionnaires with physical examination findings and laboratory samples obtained from participants. The data are weighted to allow for computation of appropriate population estimates. This study was approved as exempt research by the Virtua Health institutional review board.
Sample
The subjects included in this study are nongeriatric (aged 20 to 65 years) adult participants in the 2005–2010 NHANES who answered "yes" to the question, "Have you tried to lose weight in the past year?" Female participants were excluded from analysis if they reported being pregnant at the time of the questionnaire or had given birth in the previous year. Participants who had a body mass index (BMI; weight in kilograms/height in square meters) in the underweight category (BMI <18.5) at the start of the weight loss year were also excluded. BMI at the start of the weight loss year was calculated from reported height at the time of survey and reported weight from 1 year before the survey. Other exclusions included participants with any missing demographic data or who did not identify at least one specific method they used to try to lose weight. There were 3367 participants who met inclusion and exclusion criteria, which represent 53,570,979 adults in the US population.
Measures
Patient Report of Weight. Participants were asked to report their weight at the time of survey administration as well as their weight 1 year before the survey. To evaluate for accuracy of self-assessed weight, a simple regression predicting measured weight from self-reported weight was performed and the R was examined.
Weight Loss Methods. Participants were asked whether they attempted to lose weight in the previous 12 months with a variety of methods. Because of the large number of possible methods, it was necessary for certain methods to be combined into broader categories. "Diet" methods included changed eating habits; ate less to lose weight; ate less fat to lose weight; ate fewer carbohydrates; ate less sugar, candy, or sweets; switched to foods with lower calories; ate more fruits, vegetables, or salads; ate diet foods or products; or followed a special diet. Participants were included in the "diet only" category if they only used one or more diet methods. Participants were included in the "exercise only" category if they reported only using exercise to lose weight. If a participant used any of the following methods, even in combination with diet and/or exercise methods, they were included in the "nontraditional methods" category: skipped meals, drank a lot of water, used a liquid diet formula, took prescription diet pills, took nonprescription diet pills, took laxatives or vomited, or started smoking cigarettes or began to smoke again. Those who used diet methods and reported exercising to lose weight, but did not use any of the nontraditional methods, were included in the "diet and exercise only" category. The weighted proportion of individuals using each technique was calculated.
Outcome Measures. The main outcome measure was the adjusted mean change in weight during the previous 12 months for individuals using each of the following weight loss method categories: diet only, exercise only, diet and exercise only, and nontraditional methods. Other outcome measures included the proportion of participants who lost weight using each method. The above measures were assessed in all of the participants and those whose self-report–based BMI at the beginning of the weight loss year placed them in the normal category (BMI 18.5–24.9), the overweight category (BMI 25.0–29.9), and the obese category (BMI ≥30.0).
Demographic Characteristics
Demographic characteristics of respondents included sex, age, ethnicity (non-Hispanic white, non-Hispanic black, Mexican American, and other), family income as indicated by poverty-to-income ratio (<1.0 indicates poverty), marital status (married/living with partner vs not married), and education level (high school graduate and higher vs less than a high school education).
Statistical Analysis
Because the NHANES has a complex sampling design that makes the resulting sample representative of the noninstitutionalized US population, all of our results are expressed as nationally representative estimates. Analyses were performed using SUDAAN (version 11.0, RTI International, Research Triangle Park, NC) to account for the weighting and complex sampling design.
Unadjusted least square mean change in weight during the previous 12 months was calculated for each weight loss method and t tests were used to test for differences in means, using diet and exercise only as the reference group. The proportion of participants who lost weight during the previous 12 months was calculated for each weight loss method and χ tests were used to test for differences in proportions of successful weight loss. For all of the analyses, the weight loss method category of diet and exercise only was used as the reference category. Data analysis was performed in August 2013.
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