Most jobs today require much less physical activity than a few decades ago, a trend that has contributed significantly to the rapid increase in America’s obesity rate, researchers from Louisiana State University reported in the scientific journal PLoS ONE. Automation and different working systems have turned many physically active occupations into predominantly sedentary ones, the authors explained.
Approximately 20% of private industry jobs today in America require a moderate level of physical effort, compared to 50% five decades ago, the researchers wrote.
Lead researcher, John S. McIlhenny, said:
“Yesterday’s jobs have been replaced by sitting or sedentary activity. “In the last fifty years, we estimate that daily occupation-related energy expenditure has decreased by more than 100 calories per day, and this reduction accounts for a significant portion of the increase in mean US body weights for women and men.”
McIlhenny and team gathered data from NHANES (US National Health and Nutrition Examination Surveys), as well as the Bureau of Labor Statistics, which included details on workers’ body weight and estimated energy expenditure requirements.
The researchers worked out that the average American worker/employee today requires at least 100 fewer calories to do their job each day than in the early 1960s. One hundred calories may not sound like much, but if it is not used up somehow, it can easily accumulate as body fat – after 180 working days 18,000 extra calories are equivalent to 2 kilos (4.4 lbs) of fat
The investigators attempted to predict the extra weight accumulated by workers because of the lower daily calorie requirements compared to the early 1960s – they used computer models. Their results were very close to how much the average American worker weighs today.
The number of job-related calories required by an average worker in 2000-2006 were 142 lower than in 1960-1962. In 1960 the average worker weighed 76.9 kg (169.2 lbs). In 2003-2006 the average worker’s body weight was 91.8 kg (202 lbs) – very close to the 89.7 kg (197.3 lbs) they had calculated would have been the estimated weight after burning 142 fewer calories each day.
The authors stress that there are other causes, apart from a lower daily calorie requirement, for the current obesity epidemic in the country. Lack of physical activity is also a key factor. They add that their study did not investigate non-working time lifestyle habits that may also have contributed, such as leisure time activity, how people commute today in comparison to fifty years ago, etc. Fifty years ago more people commuted by bus/train and got off and walked to their place of employment, for example.
US authorities advise their citizens to do at least 150 minutes of moderate intensity physical activity each week, or 75 minutes of vigorous exercise. Apparently, only about 5% of Americans do this.
An obese individual has a BMI (body mass index) of 30 or more – their bodyweight is at least 20% higher than it should be.
Obesity can be caused by:
- Calories – persistently, over the long term, consuming more calories than you burn up each day.
- Sleep – several studies have shown that long-term sleep deprivation tends to make people put on weight.
- Physical inactivity – not only does physical activity consume calories, it also has an effect on how the hormones in our body deal with food. For example, physical activity has a beneficial effect on insulin levels, it keeps them stable. Irregular insulin levels are closely linked to weight gain.
- Endocrine disruptors – found in some foods, can increase the likelihood of gaining weight.
- Some medications – some commonly prescribed drugs cause weight gain, such as those for treating mood disorder, seizures, migraines, hypertension, and diabetes.
- Family history (genes) – studies of identical twins who were raised in different families have demonstrated that your genes also play a key role in deciding how much you weigh. Bodyweight characteristics often run in families. If both your parents are obese, you chances of becoming obese yourself are greater.
- Some health conditions – individuals with hypothyroidism (underactive thyroid gland), PCOS (polycystic ovarian syndrome), or Cushing’s syndrome are more likely to gain weight.
- Emotional/mental factors – boredom, anger or stress can alter a person’s eating habits. Some say that mental stress can cause hormone imbalances which can affect bodyweight (further studies required).
Obesity rates in America continue to rise. A report last year said that 27 states saw an increase in the percentage of people classed as obese, with only one state reporting a fall (Link to article).
“Trends over 5 Decades in U.S. Occupation-Related Physical Activity and Their Associations with Obesity.”
Timothy S. Church, Diana M. Thomas, Catrine Tudor-Locke, Peter T. Katzmarzyk, Conrad P. Earnest, Ruben Q. Rodarte, Corby K. Martin, Steven N. Blair, Claude Bouchard.
PLoS ONE 6(5): e19657. Published online 25 May 2011.DOI:10.1371/journal.pone.0019657
Written by Christian Nordqvist