One of the more trying, and yet rewarding components of personal training is assisting clients with successful long-term weight loss. And with 100,000,000 obese individuals in the United States this clientele and specific goal is not going to go away. The old adage of calories-in versus calories-out seems like a logical approach, but is not quite as simple as the statement itself. Most professionals realize that weight management dynamics are more complicated than a basic in and out equation and that the type of activities, albeit movement based or tension based, play a role in both metabolic and endocrine responses, as do the foods and drinks an individual consumes. This being said, the first step to successfully engaging and guiding clients to goal oriented outcomes is to establish tracking metrics. Metrics are quantifiable measures that provide useful information in gauging treatment effectiveness and monitoring changes. For example, to implement the calories in, calories out equation it becomes relevant to be able to measure the factors of thermodynamics - how much energy was put into the body (metric 1) and how much energy was expended by the body (metric 2).

Researchers will tell you a major part of the challenge is that physical activity, resting metabolism, and accurate body composition are quite difficult to assess in field-based environments. In the laboratory, variables can be controlled and the equipment/techniques employed are very accurate. This is great for research, but how do we establish a successful model for the field, so practitioners can monitor, measure and track progress in weight management? The traditional method involved teaching a client about serving sizes, how to use food logs to collect serving and food data, and input this information into dietary software to determine the “calories in.” The next step was to compare that value (average daily intake) to an average expenditure, most often calculated using relative factors in a predictive equation (modified Harris-Benedict, Molnar, or Cunningham formula) combined with an activity multiplier based on a mix of subjective/objective data.

Although the “calories in” approach is still consistent, the “calories out” concept has evolved. Two common methods now used for caloric expenditure are the MET log and the use of accelerometers to predict caloric expenditure. The MET log is based on indirect calorimetry, where known values are applied to MET calculations (like those found on aerobic machines) for planned activity and an average MET value for free living (validated by a pedometer or accelerometer). Pedometers and accelerometers provide feedback about movement. A pedometer is fine for a relatively inactive person or one who does not engage in varied movement exercise as it simply measures the physics of body motion. As a person walks, leg action causes the body’s core to accelerate and decelerate vertically. The foot strike causes a sharp change in motion allowing the device to detect a quantifiable movement. An accelerometer on the other hand, measures the amount of acceleration force by magnitude and direction. An accelerometer is better for active people as it can determine speed and incline and provide better feedback about different types of activity than a pedometer is capable of providing.

Due to their versatility, accelerometers have become the prominent strategy for assessing physical activity under free living conditions. This said, researchers suggest more work is needed to overcome several limiting challenges for optimal validity. This is particularly true for special populations, which include monitoring the physical activity of children. For children, the complexities associated with the more sporadic and intermittent physical activity patterns cause issues with accurate assessment, as does the inherent variability associated with growth and maturation. These factors, among others, present difficulties in isolating variables in research, particularly for varied stage pubescence, making the creation of general algorithms for the population a challenging task.

Recent developments in assessing energy utilization have included adding measurements of heat to the activity markers in the accelerometers to better predict total energy expenditure in adults. The use of heat sensors and movement pattern-recognition monitors provide added data to the assessment. The SenseWear Pro Armband® (SWA) and SenseWear Mini® produced by BodyMedia integrate motion sensor data, along with heat sensors to predict the energy cost of exercise and free living activity. The addition of the heat sensors provide interpretive information that cannot be obtained from the movement sensors. The combination of sensors enables the device to predict energy utilization from different contributing factors such as complex or loaded movements. Another advantage over a traditional accelerometer is that SenseWear monitors report actual wear time and calculate accordingly, which makes these devices a better choice over uniaxial accelerometers for assessing physical activity in the field.

Research has validated the energy expenditure estimates produced by the SWA. Several clinical trials support an accuracy of ~90% for adults based on comparisons of both indirect calorimetry (oxygen use) and doubly labeled water (measurement of elimination rates). Although more work is necessary to improve the ability of these monitors to accurately measure high levels of work, when compared to traditional accelerometers, the multi-sensor devices have demonstrated advantages in accurate measures. In fact, a study published in the Journal of Medicine and Science in Sports and Exercise (April 2010), demonstrated considerable accuracy for a device of this nature, as doubly labeled water and the SWA showed agreement over a broad range of total energy expenditure. This being said, it seems there are still some limitations to the devices which may be curable through adjustments in the algorithms. This may also enhance the accuracy of SWA for physically active youths, as results of validation studies within this population have been somewhat equivocal. Studies, although somewhat limited, have suggested both significantly underestimation for energy expenditure for a variety of standardized physical activities as well as consistent overestimation in similar population sample sizes. According to a recent report, also published in the Journal of Medicine and Science in Sports and Exercise (June 2010), the SWA together with Innerview Professional software 5.1 (not SenseWear Professional 6.0) increased measurement accuracy in obese children measured over a two week period. This suggests that even the difficulties of measuring special populations may be overcome by the use of additional data.

Regardless of the true validity of the aforementioned devices, the more important factors associated with their measurement may be the aspects of quantification and reliability. Having a number to strive for is likely to motivate an exerciser to work harder to reach a particular objective and also creates accountability. The consistency of the measure allows for a daily assignment of calories expended or steps taken, so that both the trainer and client understand the contribution of activity to measured changes in weight or body composition. For successful weight management it is extremely important that clients have measureable objectives on a daily basis that are premeditated, quantifiable, monitored and tracked. This takes the guess work out of physical activity and caloric expenditure. For instance, walking 7,000 or more steps is very easy to measure using a pedometer and is very quantifiable; so a client either accomplished that objective or did not. Likewise, an objective of 2,300 kcal expenditure or more per day is easy to determine using an accelerometer or SWA. The device objectively tells you whether it has been completed or not.

The fact based concept does not require absolute validity but rather a consistent measure; something that can be tracked on a day-to-day basis. If a goal value is being reached and weight loss is not occurring there is a simple solution - increase activity objectives to a point that is tolerated and attainable and manage intakes accordingly. This should be the obvious course if the current assigned value is being reached and is not significant enough to make a change. From this point, add other controllable daily variables to the strategy matrix. Use resistance training, select foods that add to thermic dynamics (TEF), avoid processed foods, spread daily intakes over smaller portions and greater frequency to stabilize blood glucose levels, etc… All these activities will contribute, but again a daily energy expenditure objective should be the foundation of any weight management plan. Simply assign the work and make sure it is done each and every day. Physical homework is necessary in the same way scholarly homework is necessary, if it wasn’t everyone would already be lean and well educated.