James Levine and Michael Jensen of the Endocrine Research Unit of the Mayo Clinic and Foundation, along with Norman Eberhardt of the Mayo Clinic’s Departments of Medicine and Biochemistry and Molecular Biology set out to provide a study that would explain why some people are better suited to eat more and not gain weight, while others can add to their caloric intake and efficiently store more fat. In order to understand this, they began with a sample of sixteen non-obese adult volunteers (twelve men, four women) that agreed to add one thousand calories to their daily maintenance requirement and only perform volitional exercise that met the low volume, low intensity requirements of the study.
The idea behind the study was that if they controlled the caloric intake by adding 1,000 calories and then controlled the caloric expenditure that was the result of volitional exercise, they would be able to understand how much non exercise activity thermogenesis affected weight gain. They did consider the idea that the body will use energy in order to process the increased number of calories, but they found that the increased expenditure was negligible, and fairly consistent across the board, indicating that while it did up the expenditure, it did so in a way that did not help to narrow down why some people store more weight than others. They found that on average 432 calories of the 1,000 excess calories were stored while 531 were burned via increased energy expenditure, accounting for 97% of the calories indicating “optimal compliance” (Levine, 1999) They also found that fat gain ranged from .36 kg to 4.23 kg, and not surprisingly the weight gain was inversely related to an increase in total calorie expenditure. (Levine, 1999)
Levine, Jensen and Eberhardt based their understanding of caloric expenditure off the idea that if they controlled the expenditure from volitional exercise, they would better understand how NEAT came into play. In the end, they study showed that with increased caloric intake, NEAT explained why some subjects gained more fat than others. However, the activity that was explained as NEAT seemed to be uncontrolled to me, for instance, the article indicated that one person was expending an additional 692 calories a day via strolling-equivalent activity. Now, it was outside of the study’s parameters for volitional exercise, but in my opinion 692 calories worth of “strolling-equivalent activity” should be classified as something closer to exercise than non-exercise activity. (Levine, 1999)
The findings of the study were nothing too surprising, if you eat more and then up your activity, whether that is through extra exercise activity or through parking your car at the end of the lot instead of up front, or taking the stairs instead of the elevator, you are going to experience less fat storage than you would if you decided to eat more and move the same amount (or less). They discussed possible errors related to not measuring calorie expenditure perfectly and a possible significance of a difference in gender differences, but I feel as if the study was too broad in what would be considered NEAT. I would suggest more effort be put into finding a sample that regularly completed normal tasks, and that didn’t intend on changing their NEAT habits throughout the study. The findings of the study make sense, but I don’t believe it really narrowed why some people store more fat than others. There is obviously more research that can be done on the topic!
Levine, J. A., Eberhardt, N. L., & Jensen, M. D. (1999). Role of Nonexercise Activity Thermogenesis in Resistance to Fat Gain in Humans. Science,283(5399), 212-214.
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