The biological control of voluntary exercise, spontaneous physical activity and daily energy expenditure in relation to obesity: human and rodent perspectives

Abstract

Summary Mammals expend energy in many ways, including basic cellular maintenance and repair, digestion, thermoregulation, locomotion, growth and reproduction. These processes can vary tremendously among species and individuals, potentially leading to large variation in daily energy expenditure (DEE). Locomotor energy costs can be substantial for large-bodied species and those with high-activity lifestyles. For humans in industrialized societies, locomotion necessary for daily activities is often relatively low, so it has been presumed that activity energy expenditure and DEE are lower than in our ancestors. Whether this is true and has contributed to a rise in obesity is controversial. In humans, much attention has centered on spontaneous physical activity (SPA) or non-exercise activity thermogenesis (NEAT), the latter sometimes defined so broadly as to include all energy expended due to activity, exclusive of volitional exercise. Given that most people in Western societies engage in little voluntary exercise, increasing NEAT may be an effective way to maintain DEE and combat overweight and obesity. One way to promote NEAT is to decrease the amount of time spent on sedentary behaviours (e.g. watching television). The effects of voluntary exercise on other components of physical activity are highly variable in humans, partly as a function of age, and have rarely been studied in rodents. However, most rodent studies indicate that food consumption increases in the presence of wheels; therefore, other aspects of physical activity are not reduced enough to compensate for the energetic cost of wheel running. Most rodent studies also show negative effects of wheel access on body fat, especially in males. Sedentary behaviours per se have not been studied in rodents in relation to obesity. Several lines of evidence demonstrate the important role of dopamine, in addition to other neural signaling networks (e.g. the endocannabinoid system), in the control of voluntary exercise. A largely separate literature points to a key role for orexins in SPA and NEAT. Brain reward centers are involved in both types of physical activities and eating behaviours, likely leading to complex interactions. Moreover, voluntary exercise and, possibly, eating can be addictive. A growing body of research considers the relationships between personality traits and physical activity, appetite, obesity and other aspects of physical and mental health. Future studies should explore the neurobiology, endocrinology and genetics of physical activity and sedentary behaviour by examining key brain areas, neurotransmitters and hormones involved in motivation, reward and/or the regulation of energy balance.

Are Voluntary Wheel Running and Open-Field Behavior Correlated in Mice? Different Answers from Comparative and Artificial Selection Approaches

“…Moreover, the relation of wheel running to homecage activity may well depend on the size and configuration of the wheel and the home cage. In any case, it is crucial to maintain clear distinctions among different measures of locomotor behavior in addition to whether they occur in familiar versus novel environments (Stanford 2007;Garland et al 2011b). Table S3.…”

“…In comparing different species of rodents, Wilson et al (1976) suggested that the open-field test should simply be viewed as an analytical tool for assessing individual-specific behavioral reactions when introduced into a novel environment. Clearly, the open-field test does not give a simple index of the status of locomotor output (Stanford 2007; see also Garland et al 2011b). Behavioral ecologists first used a type of open-field test as a measure of ''exploratory activity'' and showed that variation in population growth rate among populations of Microtus ochrogaster was associated with variation in average latency to enter the testing arena (from an entry tunnel) and the number of fecal pellets deposited in the arena (Krebs 1970).…”

“…Owing to the irreconcilable nature of dissimilar findings over a century of research, Sherwin (1998) suggested that ''wheel running may be an artifact of captive environments or of the running-wheel itself, possibly resulting from feedback dysfunction.'' In any case, many species of rodents will readily use running wheels promptly after they become available, and this behavior can occupy a substantial proportion of their time budget (Dewsbury 1980;Mather 1981;Sherwin 1998;Garland et al 2011b). Although behavioral ecologists have paid little if any attention to wheel running, some workers have speculated that it may reflect aspects of daily movement distance or home range size that would occur in nature (e.g., Swallow et al 2009;Feder et al 2010).…”

PGC-1α and exercise in the control of body weight

“…An entire evolving scientific branch is dedicated to the investigation of such 'inactivity physiology'. 97,98 A recent review on the subject addresses the risk of sitting in decreasing energy expenditure by diminishing non-exercise activity thermogenesis and favoring the development of metabolic diseases and a recent study reported attenuated insulin sensitivity in healthy, non-exercising subjects who went from a normal to a low level of ambulatory activity for 2 weeks. 97,99 In the light of the increasing prevalence of metabolic disorders, the use of adjuvants to enhance exercise effects in people with a low drive to move might therefore gain profound interest for public health management in the coming years.…”

Accuracy and reliability of a videogrammetry system in the analysis of displacement of Wistar rats

“…In experiments with animals, the displacement is an important parameter in the study of behavior. Classified as spontaneous physical activity, locomotor behavior is a key element in the daily lives of animals, required for survival and homeostasis 8 . In recent decades, the development of analytical methods to analyze displacement by videogrammetry has been used in studies with different objectives: to understand the effects of psychostimulants 9 , different environments 10 , food restriction 11 , different conditions of housing 12 , and drugs 13 .…”