Bodyweight Variations and Metabolic Compensations
Weight loss is likely the most sought after goal exercise programs. Self-proclaimed gurus and DVD divas are constantly coming up with new movements and methods to optimize caloric expenditure per given time segment. And while some programs falsely flaunt +1,000 kcal/hour workouts, research has indicated these claims are simply not true. In a recent study published in Obesity (2012), investigators cited the less than expected caloric expenditure associated with common exercise regimens. Weight loss expectations remain high when engaging in routine physical activity but weight loss resulting from an exercise intervention tends to be significantly lower than predicted. Additionally, repeated studies have shown that many people who begin an exercise program lose little or no weight while others actually gain weight. Researchers comparing weight loss to actual expenditure conclude that the small magnitude of weight loss observed from the majority of evaluated exercise interventions is primarily due to low doses of prescribed exercise energy expenditures compounded by a concomitant increase in caloric intake. So while some people believe they should lose weight because they perform exercise, most of them do not engage in enough exercise to offset the calories consumed.
In a recent study to analyze the hunter-gather concept researchers fitted African tribesmen with GPS units, to measure how many miles each walked in daily pursuits of food. The metabolic activity of the tribesmen and women was monitored using doubly-labeled water to more precisely determine energy expenditure and metabolic rate. The researchers gathered data over an 11 day period to calculate each subject’s average daily physical activity, energy expenditure and resting metabolic rates. These values were then compared to the numbers taken from similar individuals living western lifestyles.
It would reason the hunter-gatherer lifestyle involves considerable physical activity, and therefore results in significant caloric expenditure during daily activities to survive. It is presumed this number far exceeds those expended by the average American office worker each day. And based on the study data, the scientists determined that the tribesmen and women in general moved more than most Americans do; with the men walking about seven miles a day and the women walking about three. Somewhat surprising was that fact that the tribesman did not significantly exceed the metabolic output of their American counterparts. In fact, the scientists calculated the Africans’ average metabolic rate being about the same as the average metabolic rate for Westerners. This suggests that simply being active may not be enough to offset the calories commonly found in the American diet. And of further interest, an active lifestyle is often associated with increased consumption of food rather than a concurrent reduction in calories. That is, even active people will add fat mass if they eat like an average American. The bottom line is exercise alone is not the answer – so the question begs “why were the African tribesmen all thin?”
According to Dr. Timothy Church of the Pennington Biomedical Research Center in Louisiana, who has long studied exercise and weight control, “It’s been known for some time that, calorie for calorie, it’s easier to lose weight by dieting than by exercise,” he says. There are likely two explanations for this which both support modern theories of weight loss. The first is insulin management. When low-calorie foods are consumed throughout the day the impact on fat storage is increased compared to the same calories consumed in fewer meals due to changes in the glycemic load. Likewise, when natural foods are consumed over processed sources the total calories and glycemic effect are lower, while the thermic effect may be equal or higher. For instance, a half a cup of orange juice is equated to an orange serving for nutrient quality but the internal dynamics between the two are dramatically different. Of additional relevance is human metabolism appears to be less affected by activity than was once believed. “There’s this expectation that if you exercise, your metabolism won’t drop as you lose weight or will even speed up,” says Diana Thomas, a professor of mathematics at Montclair State University in New Jersey, who led the study. But this is not true and explains a second concept of weight loss, survival balance. The concept of survival balance is related to losing too much weight when either; activity levels remain constant while calories are reduced, or calories remain the same and energy expenditure increases dramatically. As a natural defense to starvation, metabolism seems to decrease with weight loss. It should therefore not be surprising that the study found subjects’ basal metabolic rates dropped as they lost weight, even though they engaged in daily physical activity. The idea in the past was that continuous exercise expenditure would lead to predictable and consistent weight loss. In this study, even though the subjects were burning significant calories due to activity, their total daily caloric expenditure was lower than it would have been had their metabolism remained constant; consequently reducing the weight loss effect compared to predicted expectations. Because there is an amortization process within basal metabolism along with a given loss of bodyweight, the actual loss of fat (associated with the same energy expenditure) is not constant over an extended period.
Based on these findings, Dr. Thomas has begun to recalibrate weight loss formulas, taking into account the drop in metabolism. Using her new formulas, which can be accessed from the Pennington Biomedical Research Center website at http://www.pbrc.edu/research-and-faculty/calculators/weight-loss-predictor/, she’s working with test subjects to improve predictions about how much weight they can expect to lose from exercise. And while the actual numbers are lower, Thomas suggests, “It’s better to meet lower expectations, than to be disappointed that you’re not losing what you supposedly should.”
Based on this information it is apparent that resistance exercise aimed at lean mass maintenance, a calorie-controlled hunter and gather eating technique, and routine physical activity all function synergistically to create an effective weight loss matrix. The next goal is getting clients to understand and believe in this process. The “secret pill” is actually consistency in behaviors and an ability to avoid over-eating. It appears that will and motivation are important, but controlling expectations seems to be a major part of the equation.
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