Extraneous variables can affect the relationships between the independent (education) and dependent variables of the study (the BMI and body fat percentage) (Schmidt & Brown, 2014). To increase the internal validity of the study, it is necessary to effectively control the following variables: intelligence, pre-education, and socio-economic status. Randomization will help to avoid the distortion of the relationships between education, BMI, and body fat percentage. By randomly assigning the participants to the intervention and control group, it will be possible to both avoid selection bias and control the effects of the extraneous variables.
The BMI will be used to assess the body composition of the participants. Even though the validity of the instrument has been questioned by numerous studies, it is more reliable than the waist circumference and cheaper than underwater weighing and impedance measurement (CDC, n.d.; Szko & Nieto, 2014). Furthermore, the instrument’s reliability is lower than that of skinfold thickness measurements and can range from 0.37 to 0.83; therefore, the sum of skinfolds will be calculated to evaluate body fat percentage of the participants (Pate, Oria & Pillsbury, 2012). To minimize a technical error, the weight will be measured with “minimum clothes using a calibrated electronic scale with digital readout” (Ranasinghe et al., 2013, p. 799).
Body fat percentage will be measured with the help of a skinfold caliper, the application of which has gained wide acceptance among nutrition specialists. According to Pate et al. (2012), a technical error of the measurement is extremely low if it is obtained by trained practitioners. A skinfold caliper has also been proven reliable (ICC=0.997) (Stalker, 2012).
The two instruments score highly in terms of administrative feasibility. They can be quickly administered with the help of the following equipment: a stadiometer, a scale, and a skinfold caliper (Pate et al., 2012). Given that reliable instruments for body composition measures are available, there is no need to design and test new assessment methods.
Description of the Intervention
All participants assigned to the intervention group will participate in a dietary education program. The program will be based on a behavioral theory, which will help to delineate specific approaches to behavioral change (Fitzgibbon et al., 2012). Also, the application of the theory will be instrumental in choosing an effective mix of educational approaches. The intervention will take a form of 5 weekly group sessions followed by a 30-minute resistance training. The sessions will be conducted by a registered dietarian who will explain to the participants all benefits of healthy diets. The following topics will be discussed: “reading and understanding food labels, estimating portion sizes, and behavioral strategies for increasing consumption of fruits and vegetables” (Straight et al., 2012, p. 877). The program’s objective is to elicit long-term weight loss and change the body composition of the intervention group.
Data Collection Procedures
Data for the study will be collected in person. All participants will be explained the steps involved in the measurement of the BMI and body fat percentage. The measurements will be carried out by a nurse who will ensure that data is recorded appropriately. Weight measurements will be taken with an electronic scale, which will be placed on a flat surface (Rippe & Angelopoulos, 2012). BMIs will be calculated after measuring heights with a stadiometer (Rippe & Angelopoulos, 2012). Slim Guide caliper will be used to quantify the body fat percentage of the participants (Summerfield, 2015). All measurements will be taken on the right side of the women’s bodies by the nurse.
CDC. (n.d.). Body mass index: Considerations for practitioners. Web.
Fitzgibbon, M. L., Tussing-Humphreys, L. M., Porter, J. S., Martin, I. K., Odoms-Young, A., & Sharp, L. K. (2012). Weight loss and black women: A systematic review of the behavioural weight loss intervention literature. Obesity Reviews, 13(3), 193-213.
Pate, P., Oria, M., & Pillsbury, L. (Eds.). (2012). Fitness measures and health outcomes in youth. Washington, DC: National Academies Press.
Ranasinghe, C., Gamage, P., Katulanda, P., Andraweera, N., Thilakarathne, S., & Tharanga, P. (2013). Relationship between body mass index (BMI) and body fat percentage, estimated by bioelectrical impedance, in a group of Sri Lankan adults: A cross sectional study. BMC Public Health, 13(1), 797-804.
Rippe, J. M. & Angelopoulos, T. J. (2012). Obesity: Prevention and treatment. Boca Raton, FL: CRC Press.
Schmidt, N. A., & Brown, J. A. (2014). Evidence-based practice for nurses. Sudbury, MA: Jones & Bartlett Publishers.
Stalker, G. L. (2012). Reliability and validity of the body caliper to evaluate body composition. Web.
Straight, C. R., Dorfman, L. R., Cottell, K. E., Krol, J. M., Lofgren, I. E., & Delmonico, M. J. (2012). Effects of resistance training and dietary changes on physical function and body composition in overweight and obese older adults. Journal of Physical Activity and Health, 9(1), 875-883.
Summerfield, L. M. (2015). Nutrition, exercise, and behaviour: An integrated approach to weight management. New York, NY: Cengage Learning.
Szko, M., & Nieto, J. (2014). Epidemiology. Sudbury, MA: Jones & Bartlett Publishers.