Burning Less and Consuming More

That is really the bottom line from the research that came out this week and several studies published last year. With regard to work time physical activity, the study by Church indicates that in the last 50 years, the work force (gender) and the type of work has changed significantly. There are more persons doing service providing work and fewer doing goods-producing work. In this case, the amount of physical effort expended on the job has changed (not including technical changes that make work easier). The researchers used METs to describe the work activity as either sedentary, light or moderate. You may remember the metabolic equivalent charts and formulas from this post. The jobs that were considered to be of the moderate MET were mining and logging, construction and manufacturing. The scientists considered moderate to be an MET of 3 to 5.9 and sedentary was an MET of less than two. Recall that a moderately paced walk of 4 miles an hour - or one mile in 15 minutes, is an MET of 4.

Reviewing data from the US over the past 5 decades, Church et. al, determined that there are more women employees now than in 1960 and on average, all workers are expending about 100 calories less in work time activity. They state that this change can explain a lot of the obesity epidemic. I disagree with how they are stating it, as if calories in are not driving the weight gain, but not with the bottom line. We are burning less calories, but we are consuming far more (mathematically). Other studies, namely Swinburn(2009), Westerterp(2009) and Prentice(2004) note that as we become more sedentary we do not moderate the difference by eating less. Prentice explained the issue of failing satiation signals, and Swinburn notes that the average intake is up 500 calories. That is where I put most of my faith. Even if work time physical activity has declined and leisure time physical activity has not increased, likely declining instead, not only are we NOT eating 100 to 200 calories less - so that we would have the right balance, we are eating even twice that MORE. The excess has a lot to do with how food is prepared and our ignorance of the amount of fat, sugar and calories in the portion of any food we are consuming.
But let us say that all things WERE equal. If a person who weighs 150 pounds lost the expenditure of 100 calories, they would need to take a brisk 15 minute per mile walk for about 30 minutes a day. Clearly, the majority of US adults do not do so. In fact, Church notes a study that has indicates only 1 in 20 US adults meet that requirement on five days a week. Instead, as Swinburn et al suggests, if we take away a sugar sweetened beverage 200 calories can be deleted.

BTW, I did make my FDA comments on the labeling initiative today and I have an appointment with my campus vending contract supervisor on Thursday :) I am still preparing.

Church, T. S., Thomas, D. M., Tudor-Locke, C., Katzmarzyk, P. T., Earnest, C. P., Rodarte, R. Q., . . . Bouchard, C. (2011). Trends over 5 Decades in U.S. Occupation-Related Physical Activity and Their Associations with Obesity. PLoS ONE, 6(5), e19657.

Prentice, A., & Jebb, S. (2004). Energy intake/physical activity interactions in the homeostasis of body weight regulation. Nutrition Reviews, 62(7 part 2), S98-104.

Swinburn, B., Sacks, G., & Ravussin, E. (2009). Increased food energy supply is more than sufficient to explain the US epidemic of obesity. The American Journal of Clinical Nutrition, 90(6), 1453-1456. doi: 10.3945/ajcn.2009.28595

Westerterp, K. R., & Plasqui, G. (2009). Physically Active Lifestyle Does Not Decrease the Risk of Fattening. PLoS ONE, 4(3), e4745