Review
Nonexercise Activity Thermogenesis in Obesity Management

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Abstract

Obesity is linked to cardiovascular disease. The global increase in sedentary lifestyle is an important factor contributing to the rising prevalence of the obesity epidemic. Traditionally, counseling has focused on moderate- to vigorous-intensity exercise, with disappointing results. Nonexercise activity thermogenesis (NEAT) is an important component of daily energy expenditure. It represents the common daily activities, such as fidgeting, walking, and standing. These high-effect NEAT movements could result in up to an extra 2000 kcal of expenditure per day beyond the basal metabolic rate, depending on body weight and level of activity. Implementing NEAT during leisure-time and occupational activities could be essential to maintaining a negative energy balance. NEAT can be applied by being upright, ambulating, and redesigning workplace and leisure-time environments to promote NEAT. The benefits of NEAT include not only the extra calories expended but also the reduced occurrence of the metabolic syndrome, cardiovascular events, and all-cause mortality. We believe that to overcome the obesity epidemic and its adverse cardiovascular consequences, NEAT should be part of the current medical recommendations. The content of this review is based on a literature search of PubMed and the Google search engine between January 1, 1960, and October 1, 2014, using the search terms physical activity, obesity, energy expenditure, nonexercise activity thermogenesis, and NEAT.

Section snippets

Obesity Pandemic and Physical Inactivity

Obesity is a global pandemic; at least 78 million American adults are affected, as are almost 17% of children and adolescents.1 Obesity is defined as a body mass index (BMI; calculated as weight in kilograms divided by height in meters squared) of at least 30.2 Several studies have established the relationship between visceral adiposity and subsequent adverse health conditions,3 with 1 in 5 deaths worldwide attributed to obesity.4 Also, obesity is associated with high social economic costs.5

NEAT: An Emerging Strategy Against PI

Interventions to overcome the net positive excessive energy balance have traditionally been focused on encouraging moderate- to vigorous-intensity PA during discretionary time combined with caloric restriction11; however, this strategy has met with limited success in long-term randomized clinical trials, with no reduction in the rate of cardiovascular events.12 Hence, a third strategy has emerged that focuses on reducing the total time spent in sedentary pursuits. This strategy includes the

What Is NEAT?

NEAT encompasses the expenditure of energy that is secondary to movement beyond purposeful exercise and resistance training activities. Activities that promote NEAT include a series of continuous and vital movements with postural changes that do not involve moderate- to vigorous-intensity exercise and occur at a trivial or low energy workload on a daily basis for minutes to hours.14, 15 These activities involve walking, climbing stairs at work or any recreational community place, fidgeting,

Total Daily Energy Expenditure and NEAT

NEAT has significant interindividual variation. To understand this variation, the 3 components of TEE must be explained: (1) basal metabolic rate (BMR), (2) thermic effect of food (TEF), and (3) PA (Figure 1).18 The BMR represents approximately 60% of TEE. The TEF also contributes to TEE, and by some estimates composes as much as 10% of TEE. The mechanism by which energy is expended with food ingestion and digestion, including mastication, digestion, absorption, and transportation of nutrients,

Purported NEAT Mediators and Brain Sites of Action

Emerging evidence suggests that exercise activity may be partly genetically influenced. This is not unexpected because previous work has demonstrated that the variation in body weight and body fat distribution is genetically determined to a certain extent.23 Recent information suggests that the nuclei possibly involved in the regulation of NEAT are located in the hypothalamus and extrahypothalamic nuclei24 in a complex network that determines the level of spontaneous PA. Multiple potential

NEAT Mechanism

Inadequate energy expenditure results in the excess energy being stored as fat. Levine et al37 demonstrated the relationship between fat gain and NEAT in obese and lean individuals exposed to similar environments. Twenty healthy volunteers (10 lean and 10 obese) were examined for 10 days by comparing body posture and motion to assess NEAT. Volunteers were instructed to continue with their usual daily activities without adopting new exercise practices. The results showed that the obese

Environmental Conditions for PI

The wide variability in work practices and leisure-time activities between individuals plays a fundamental role in NEAT differences.39 An example illustrating the magnitude of this variability in TEE would be to consider changing the occupation of an individual who works in a chair-bound job to a more active job, such as in an agricultural field. Based on data measuring the energy expenditure of different lifestyles and activity patterns,40 this type of occupational change could theoretically

PI Translation of NEAT Deficit

Sitting time is independently associated with an increased risk of diabetes48 and total mortality, regardless of PA level.49, 50 A Canadian study showed a dose-response relationship between sitting time and mortality from all causes and CVD, independent of leisure-time PA.10 This prospective cohort study followed more than 17,000 patients for an average of 12 years (204,732 person-years of follow-up.) for the ascertainment of mortality status. After adjusting for cofounders, they found a

Metabolic Benefits

The importance of the NEAT approach to weight control has already been tested, and benefits have been demonstrated at the metabolic level. Lipoprotein lipase (LPL), an enzyme that plays a central role in the pathogenesis of atherosclerosis and obesity,51 was measured in rats with different levels of PA. The results show that persistently low- to moderate-intensity activities show higher LPL activity levels compared with nonsustained intense exercises,52 thus demonstrating the effect of NEAT at

Household Activities

The promotion of activities with higher NEAT and the numerous opportunities to implement it may be another tool in the armamentarium against the obesity epidemic (Figure 3). Lanningham-Foster et al58 systematically examined the energetics of mechanization on daily tasks such as manual washing of clothes or dishes, walking to work, and climbing stairs. Performing such NEAT activities instead of using labor-saving equipment could expend considerable energy. For example, performing yard work

NEAT Feasibility in the Community

An example of the effectiveness of NEAT in a community setting where the prevalence of obesity is low is the Amish communities. NEAT is applied and accumulated throughout the day during occupational requirements, chores, errands, and transportation. Only 4% of Amish adults are obese. They walk an average of 18,000 steps per day, perhaps the highest mean value reported for a sample at this time,71 compared with non-Amish US adults, who average approximately 5100 steps per day.72

NEAT Quantification

One of the challenges faced by researchers trying to promote PA is having access to accurate and practical instruments to measure, monitor, and increase the efficiency of measuring PA in a continuous and unobtrusive manner.73 In the past decade, technologies using low-power and low-cost electronic sensors have emerged. These devices can assess PA and its determinants. Instruments such as accelerometers provide new ways to collect and estimate the intensity, duration, and frequency of PA,

NEAT as a Complement to Purposeful PA

The health benefits to support purposeful aerobic exercise are well-known,81 and NEAT should not be considered a substitute. There is broad agreement among clinicians and public health experts that moderate- to vigorous-intensity PA of at least 30 minutes 5 days per week for a total of 150 minutes is recommended by guidelines.82 The benefits of moderate- to vigorous-intensity exercise in CVD are clear.83, 84 However, the long-term success from recent randomized studies has been disappointing,12

NEAT Limitations and Future Ongoing Trials

Although several clinical trials and cohort studies have assessed the benefit of NEAT body morphometrics, blood pressure, and lipid markers, there are no robust studies assessing long-term outcomes on cardiovascular events or cardiovascular mortality. The potential benefit of obesity reduction on the musculoskeletal system and related orthopedic conditions has yet to be elucidated as well. In the past decade, attention has shifted to implementing an intensive lifestyle intervention to reduce

Conclusion

Physical inactivity may be one of the factors contributing to the global obesity pandemic. Reducing and breaking up the time spent in sedentary behaviors and preserving PA is extremely important to ameliorate obesity. Besides recommending practicing moderate- to vigorous-intensity PA, counseling and promotion of NEAT should be considered by health care providers to help control obesity. Encouragement and assistance in promoting personal and environmental behaviors of the NEAT concept should be

Acknowledgments

We thank Dr. Eric H. Yang for the creation of Figure 4.

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