Is There Still Potential Value of Physical Activity Monitoring?

Javaid Nauman

In the September 20, 2016 issue of JAMA Jakcic et al. report that “devices for physical activity  monitoring and feedback may not offer an advantage over standard behavioural weight loss approaches”. However, there are several important study limitations that should be considered when interpreting these thought-provoking and interesting results.

The study included 471 men and women aged 18 to 35 years whose BMI ranged from 25 to less than 40. They were placed on low calorie diet and prescribed increase in physical activity level in addition to group counselling. The authors traced weight loss of the participants in intervals of 6 months for 2 years. The researchers found that the weight loss in the standard group was 2.5 kg higher than the weight loss in the group with a wearable device (enhanced group). Both groups, however, improved their body composition, fitness, physical activity and diet to the same extent.

Both the enhanced and the standard group in the study seemed to be meeting the physical activity guidelines even before the start of the intervention with a relatively low baseline fitness. Both groups increased the moderate to vigorous physical activity bouts over the course of the intervention.  However,  moderate to vigorous physical activity advice given to study participants was not defined in the study. How did the study participants know that they were exercising at moderate to vigorous physical activity intensity and was the definition of moderate to vigorous physical activity different for those receiving the device versus those in the standard group?  Thus, the observed differences in the amount of time spent in moderate to vigorous physical activity bouts across the two groups could be attributed to a different definition of moderate to vigorous physical activity.

Carl Lavie

Furthermore, the enhanced group seemed to manage to keep their daily caloric intake lower compared to the standard group at 18 and 24 months, indicating device effectiveness in calorie tracking.  Furthermore, the self-reported food intake could have resulted in over-estimation of the energy ingested by the standard group.

In another very interesting article published recently, Pontzer et al. advocate a constrained total energy expenditure model in which the “total energy expenditure increases with physical activity at low activity levels but plateaus at higher activity levels as the body adapts to maintain total energy expenditure within a narrow range”. Consequently, considering such a model, physical activity energy expenditure becomes secondary to caloric intake when it comes to weight loss. In other words, diet is more important for weight loss than physical activity.

Nina Zisko

Therefore, as long as we do not have most accurate information on total daily energy expenditure as well as physical activity-related energy expenditure and caloric intake, it is not fair to conclude that wearables may not offer an advantage in weight loss regimens over standard treatment. Nevertheless, this interesting study shows that behavioral programs are an effective tool for weight loss. Finally considering the amount of weight lost by both groups, both weight loss regimens could be deemed successful compared to what is really standard care.

Ulrik Wisløff

Javaid Nauman, researcher at CERG, Chip Lavie, director of cardiac rehabilitation and preventive cardiology at the John Ochsner Heart and Vascular Institute in New Orleans, Nina Zisko, PhD student at CERG and Ulrik Wisløff, head of CERG.