In many interventions that are based on an exercise program intended to induce weight loss, the mean weight loss observed is modest and sometimes far less than the individual expected.
The individual responses are also widely variable, with some individuals losing a substantial amount of weight, others maintaining weight, and a few actually gaining weight. The media have focused on the sub-population that loses little weight, contributing to a public perception that exercise has limited utility to cause weight loss.
The purpose of the symposium was to present recent, novel data that help explain how compensatory behaviors contribute to a wide discrepancy in exercise-induced weight loss. The presentations provide evidence that some individuals adopt compensatory behaviors, i.e. increased energy intake and/or reduced activity, that offset the exercise energy expenditure and limit weight loss.
The challenge for both scientists and clinicians is to develop effective tools to identify which individuals are susceptible to such behaviors, and to develop strategies to minimize their impact.
Unless there is a better understanding of why some people fail to lose weight with exercise, the increase in the prevalence of obesity and the associated co-morbidities will be unmanageable and unsustainable. Although we acknowledge that people aspire to unrealistically high rates of weight loss, it is futile to continue prescribing exercise and/or dietary interventions using a one-size-fits-all approach, and expect people to be content when their efforts produce little or no weight loss.
The evidence is suggestive, but not conclusive, that when initiating an exercise program with the intent of losing weight, some individuals compensate by decreasing their non-Ex PA and NEAT. This is likely mediated by subject factors (e.g. age, sex, body weight) as well as factors related to the exercise program itself (mode, duration, intensity, frequency), but how each of these factors contribute to the overall effect has not been well-studied. Surprisingly, some data suggest that there are individuals who respond to an exercise program by increasing their non-Ex PA and NEAT.
Understanding how exercise impacts non-Ex PA has health implications far-beyond regulating energy balance, as evidence suggests that limiting sedentary behavior has positive effects on many health outcomes, independent of exercise. Moreover, it is not clear from the existent literature, when compensation occurs, whether this is intentional (i.e. “I exercised today, so I will take the elevator”) or not. Clearly, there is much more to be learned in this area.
The evidence also suggests that a compensatory increase in EI could also account for variability and offset the expected weight loss. Preliminary evidence suggests that some people experience an orexigenic response to exercise, making them more resistant to exercise-induced weight loss. The potential underlying mechanisms underpinning this compensatory response include appetite peptide response and non-homeostatic eating behavior traits.
Collectively, the evidence indicates that compensatory adaptive responses in EI and NEAT offset the effects of exercise and result in some individuals achieving little or no weight loss. However, to our knowledge, compensatory changes in non-EX PA and EI have not been comprehensively examined within the same study, and this is a high priority for future research.
The model of resistance to exercise-induced weight loss needs to be used strategically in future studies. Identifying the resistance to weight loss, and characterizing the adaptive compensatory responses will produce better strategies on how to individually tailor weight management programs. Indeed, energy restriction studies can also benefit from this approach.
Although a compensatory increase in food intake is disappointing to the people directly affected, it serves as an ideal model of resistance to weight loss, and provides an opportunity to help explain why exercise doesn’t work for everyone.
It could also be used to inform strategies to help obese individuals who may avoid exercise based on their experience of disappointing weight loss. We propose that it is possible to pool the current evidence and use it strategically in the form of evidence-based screening procedures to identify resistance to weight loss due to a compensatory increase in food intake.
This approach is novel because it targets resistance to weight loss and individuals susceptible to compensation during exercise interventions. Identification and characterization of behavioral and physiological characteristics will provide evidence-based screening information that will facilitate the identification of individuals vulnerable to compensation and resistant to weight loss.
Early identification of weight loss resistance will eventually permit tailoring of obesity prevention and treatment strategies to suit individuals who are more susceptible to compensatory eating. We also need to better educate people that weight loss is not the only health benefit of exercising. Indeed, there is strong evidence that people experience other health benefits (e.g., reduced blood pressure and waist circumference) despite not attaining the expected, or any, weight loss
Our concern is that efforts to increase physical activity amongst the general population have been undercut by negative media reports portraying exercise as ineffective for weight loss, which may be interpreted by some as therefore ineffective for improving health.
We all have a responsibility to eradicate this ‘bad spin’, and to educate the public that weight loss is not the sole benefit of exercising; indeed, people can experience health benefits in the absence of weight loss.