Overweight

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The financial burden of overweight elderly Americans

January 16, 2008 in Obesity | Permalink

How do we measure the financial burden of elderly obesity? At first this seems like an easy question to answer. Find the average medical spending of the obese elderly and compare that to the spending of an elderly individual of healthy weight.

Yet causation is difficult to show.

True, it is possible that the obese may be more likely to get sick and thus incur higher costs, but it is also possible that sick people can gain weight–since it is difficult to exercise when sick–which can cause more obesity. Thus, the original sickness and not the obesity may be the true cause of the additional medical expenses.

A 2007 Health Services Research paper by Yang and Hall try to examine this question. They use panel data from the Medicare Current Beneficiary Survey (MCBS). The authors use a maximum likelihood estimation strategy, modeling current BMI as a function of last year’s BMI and Acute Medical Events. Acute Medical Events are also a function of BMI in a separate estimating equation. Health care expenditure is a function of BMI, BMI-squared, functional status, chronic and acute disease and demographics.

To identify this system of questions, the authors uses the following exogenous variables: average food prices, density of fast food restaurants and air quality. Using these instruments, the authors find that “elderly men who were overweight or obese at age 65 had 6–13 percent more lifetime health care expenditures than the same age cohort within normal weight range at age 65. Elderly women who were overweight or obese at age 65 spent 11–17 percent more than those in a normal weight range.”

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PE Requirements and Overweight Youth

January 4, 2008 in Obesity | Permalink

Do state physical education (PE) requirement help to decrease the percentage of children and teens who are overweight?

This is the question Cawley, Meyerhoefer and Newhouse investigate in their 2007 Health Economics paper.

One would certainly not be surprised if PE requirements decrease the prevalence of obesity, but this may not be correct.  PE requirements may have no effect if schools do not comply with the state mandates, or increased PE exercise may lead to decreased exercise outside of school (substitution).  Further, it is possible that PE classes may do little to promote exercise.  For instance, 12 states allow students to earn PE credit online.

To find the truth, the authors use Youth Risk Behavior Surveillance System data from the 1999, 2001, and 2003.  The authors attempt to find the local average treatment effect (LATE) by using state PE requirements as an instrument for whether or not a given student has taken a PE class.

Cawley and co-authors conclude that “high school students with a binding PE requirement report an average of 31 additional minutes per week spent physically active in PE class. Our results also indicate that additional PE time raises the number of days per week that girls report having exercised vigorously or having engaged in strength-building activity. We find no evidence that PE lowers BMI or the probability that a student is overweight.”

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Marriage and Obesity

November 28, 2007 in Obesity | Permalink

Are married people more likely to be obese than single individuals? More to the point, does being married cause obesity? Married individuals are generally older than never-married individuals and since age is correlated with obesity, there could be a spurious relationship between marriage and obesity.

One may think that married individuals are not on the “single’s market” and thus may not have a strong incentive to maintain an athletic physical appearance to attract mates. As stated in Sobal (1984), “We may hypothesize that as a marital relationship becomes solidified the partners may feel less need to maintain external appearances important in attracting a mate.” On the other hand, a paper by Rand, Kuldau and Robbins (JAMA 1982) found that individuals who had jejunoileal bypass surgery to decrease obesity had improved marriage relationships. Thus, those who value their marriage may wish to avoid being overweight to make the marriage experience more pleasurable.

If healthier individuals can more easily attract a mate, than it would be the case that married individuals will be less overweight than single individuals. Averett and Korenman (Int J Obesity 1999) found that obesity is associated with a lower probability of marriage. Gortmaker et al. (NEJM 1993) use the NLSY to conclude that individuals who where overweight in their adolescent years are 20% less likely to be married seven years later than a healthy-weighted individual. Cawley, Joyner and Sobal (Rationality and Society 2006) confirm that for adolescents “dating is less likely among heavier girls and boys and among shorter girls and boys.”

Sobal, Rauschenbach and Frongillo (Soc Sci Med 1992) categorizes the relationship between obesity as marriage through two distinct mechanisms: “marital selection” and “marital causation.” Non-overweight people are more likely to attract a mate, and thus “select” into marriage. However, if marriage “causes” weight gain–due to a more sedentary lifestyle, lower mate attraction incentive, childbirth, etc.–than a researcher may find that married individuals are more overweight on average.

The best way to control for these two conflicting effects is to use a panel data set. Cawley (JHR 2004) employs the 1979 NLSY, using lagged BMI as an instrument for current BMI and individual fixed effects to control for time-invariant individual characteristics. Other studies have used sibling weight (Avarett and Kroenman (JHR 1996), or spousal weight as an instrument for current BMI. Using data from the National Survey of Personal Health practices and consequences, the Sobal, Rauschenbach and Frongillo paper finds that “it appears that there is a relationship between fatness and marital status for men, with married men fatter and more obese.”

Nevertheless, more research is needed to refine the exact manner in which marriage affects obesity.

  • Averett S and Korenman S. 1996. “The Economic Reality of the Beauty Myth.” J Human Resources. 31(2): 304-330.
  • Averett S and Korenman S. 1999. “Black-white differences in social and economic consequences of obesity.” International Journal of Obesity. vol 23, pp. 166-173.
  • Cawley J. 2004. “The Impact of Obesity on Wages” J Human Resources. 39(2): 451-474.
  • Cawley J, Koyner K, Sobal J. 2006. ”Size Matters: The influence of adolescents’ weight and height on dating and sex.” Rationality and Society. Vol. 18, No. 1, 67-94.
  • Gortmaker SL, Must A, Perrin JM, Sobol AM, Dietz WH. 1993. “Social and Economic Consequences of Overweight in Adolescence and Young Adulthood.” NEJM. 329(14): 1008-1012.
  • Rand CS, Kuldau JM, Robbins L. 1982. “Surgery for Obesity and Marriage Quality.” 247(10): 1419-1422.
  • Sobal J. 1984. “Marriage, Obesity and Dieting.” Marriage and Family Review. 7:115-139.
  • Sobal J, Rauscehnbach BS, Frongillo EA. 1992. “Marital Status, Fatness and Obesity.” Social Science and Medicine. 35(7): 915-923.

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Why are we Obese?

November 20, 2007 in HC Statistics, International Health Care Systems | 2 comments

The simple answer for this is that calorie intake is higher than the number of calories burned. But why are people getting fatter? In which countries are people the fattest?

This is the questioned tackle in a working paper by Sara Bleich and colleagues “Why is the Developed World Obese?” Obesity is a serious disease:

Excess body weight is the fifth most important risk factor contributing to the burden of disease in developed countries. Rising body mass index steadily increases the risks of type 2 diabetes, hypertension, cardiovascular disease, and some cancers.

Unsurprisingly, the U.S. has the highest rates of obesity throughout the data collected, but the rate of increase is very similar across all countries. Recent news reports (“Over 20m Chinese suffer diabetes“) even show that developing countries such as China are starting to experience higher rates of diabetes and obesity.

The main cause of increased obesity rates is increased food consumption. This is mostly due to decreasing real food prices over the past century. Another factor is the increased female labor force participation rate. One story to go along with this is that as more women work, families cook less and instead eat out more. If dining out occurs in high calorie restaurants and fast food establishments, calorie intake will increase.

The other facto influencing obesity is decreased activity. The main societal reason for a decrease in physical activity is the decrease in the number of active jobs. As the number of manual labor and manufacturing jobs has dwindled in the later half of the twentieth century, many more people are working at desk jobs where there is little physical activity. Further, increasing urbanization rates over time has also lead to decreased physical activity. Perhaps surprisingly, the number of cars per capita or the internet usage rate has no effect on obesity.

The authors claim that a junk food tax may help to decrease obesity and improve societal health. I am skeptical of this solution. Which foods will be categorized as junk foods? Who will decide this? I would guess there will be much lobbying by large food companies to have their products labeled as non-junk foods. Further, a junk food tax would hit the poor more heavily than the rich.

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