The number of adults and children who are overweight or obese continues to increase and has reached epidemic proportions. Obesity is due to a sustained positive energy balance (energy intake > energy expenditure) and is typically coupled with low levels of physical activity (i.e. sedentary lifestyles). The combination of obesit and inactivity has resulted in increased morbidity and mortality from hypertension, stroke, coronary artery disease, dyslipidemia, type 2 diabetes, sleep apnea and a number of other conditions. To reduce these health risks, individuals are advised to monitor and manage their weight by altering lifestyle and engaging in daily physical activity. Posture allocation (time spen lying, sitting and standing) reflects an individual lifestyle and is related to obesity, which suggests that the ability to monitor posture allocation may be useful for weight management. Instruments that monitor body weight and quantify physical activity (e.g. accelerometers) have proven to be beneficial for individuals engaged in weight management programs but have limited accuracy in free-living conditions. A single device that accurately monitors body weight, posture allocation, physical activity (i.e. movement), and energy expenditure would be an extremely useful tool for weight management. Our long-term objective is to develop a simple, inexpensive, unobtrusive device that can easily be incorporated into conventional footwear and can accurately measure body weight, posture allocation, physical activity and daily energy expenditure. Such a device could be used to quantify and modify physical activity and lifestyle behavior in overweight and obese individuals and others with sedentary lifestyles. We propose that by developing a footwear-based hardware system that measure plantar pressure and acceleration of the foot, combined with a software system that classifies activities and energy expenditure and provides feedback via a mobile phone, we will offer a device that can assist in successful weight management in free-living adults. The proposed methodology is based on inexpensive technology that would enable research, clinical and consumer applications for estimating daily energy expenditure and behavior modification. PUBLIC HEALTH RELEVANCE: Obesity is a chief contributor to preventable deaths in the United States and poses a major health challenge associated with increased morbidity and mortality. Obesity is a result of positive energy balance and there is an urgent need to develop tools that can ultimately be used to prevent and treat obesity by changing physical activity behavior.