The prevalence of overweight and obesity remains epidemic in the United States, with some of the highest rates seen in older adults. While this phenomenon is certainly multifactorial, a good deal of evidence suggests that insufficient physical activity (PA) contributes significantly. Pilot data recently collected in a laboratory indicates a strong, inverse relationship between daily step counts and body fatness and cardiometabolic risk (CMR) factors when step counts are expressed relative to fat mass in young adults. This expression of PA may be especially predictive of body composition because it is influenced by factors that influence appetite and energy intake, energy expenditure, and the energy "reservoir" that is represented by body fat stores, all three elements of the "settling point" model of body weight. The strength of this relationship suggests that prescription of step counts that consider current body weight and composition, and weight loss goal, may yield predictable changes in weight and CMR in adults eating ad libitum. The long-term objective of this study is to quantify the relationship between daily step counts and body composition in young, middle aged, and older adults who are overweight/obese and develop a regression model that can be used to prescribe physical activity (daily step counts) for achieving a specific target body weight and predictably improving CMR risk for young, middle-aged, and older adult men and women over eight months while eating ad libitum. To achieve this objective, investigators will undertake two specific aims: 1) quantify the relationship between average steps·kg fat mass-1·day-1 and body composition/CMR profiles in healthy, overweight, and obese adults 20-39 years, 40-59 years, 60-79 years, and 80-plus years old, using inexpensive, widely available triaxial pedometers while eating ad libitum, and 2) quantify the efficacy of employing targeted step counts expressed as steps·kg fat mass-1·day-1 using the model developed in Aim 1 for producing predictable improvements in body composition and CMR factors in overweight and obese adults 20-39, 40-59, 60-79, and 80-plus years old, over 8 months while eating ad libitum. This study will result in a regression model that may significantly improve the way that PA is prescribed for weight management, with vast clinical and public health implications.
ages of 20 years and older
otherwise healthy adults on prescription medication to treat hypertension or osteoarthritic conditions are eligible to participate
sedentary people, or people who report engaging in regular walking (no regular structured exercise for at least the past six months)
relatively stable weight over the previous 6 months (less than 5% fluctuation in body weight)
any diagnosed cardiovascular, metabolic, renal, or pulmonary disease, or any diagnosed cognitive dysfunction
women who are pregnant or plan on becoming pregnant
people taking prescription medication to regulate plasma glucose, or that affect metabolism (e.g., thyroid medication)
people who have undergone an increase or decrease in body weight of ≥ 5% over the previous six months
Single group
Step counts for predictable changes in body weight/compositon and cardiometabolic risk
BehavioralBaseline body weight/composition will be used to establish a step count target that is expected to lead to a predictable 5% weight loss. Participants will be asked use their pedometers and to strive to achieve a step count target for 8 months.
weight
In phase one of the study, weight will be assessed for purposes of developing a regression model. In phase two of the study, weight will be assessed to establish a step count target, and to track changes during the 8-month intervention.
body composition
In phase one of the study, body composition (percentage of body weight comprised of fat) will be determined for the purposes of developing a regression model to allow prediction of body composition. In phase two of the study, body composition (percentage of body weight comprised of fat) will be assessed to determine baseline levels, and to allow for tracking changes over the 8-month intervention.
Step counts
Step counts (steps per day) will be recorded using pedometers that will be carried on the hips or torso. Step counts will be recorded for four weeks during phase one of the study, and for eight months during the intervention phase of the study (phase two).
cardiometabolic risk profiles
several markers of cardiometabolic risk (cholesterol, glucose, triglycerides, c-reactive protein) will be measured at baseline, and 8 months later to quantify the effects of an 8-month walking program on plasma lipids and c-reactive protein
insulin
In phase one of the study, fasting plasma insulin will be measured after 4 weeks of carrying a pedometer. In phase two of the study, insulin will be measured before and after an 8-month walking intervention.
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