Fit vs. Fat

Dave Alexander (shown above left) - a 55-year-old, 5’8’’, 260 pound man - has become the center of attention in the fit versus fat controversy. Despite a BMI of 40 (30 is considered obese), Mr. Alexander has competed in 276 triathlons in 37 different countries over the last 7 years. His intense regular weekly training routine (swims 5 miles, runs 30 miles, and bikes 200) enabled him to recently complete a super triathlon in which he biked 448 miles, ran 104.8 miles, and swam 9.2 miles. When asked about his self image, Dave Alexander replied, “I don’t care what people say about me, as long as it inspires them to go out and exercise.”

INTRODUCTION

In 2002 a study by the American Journal of Epidemiology titled "Fitness and Fatness as Predictors of Mortality from All Causes and from Cardiovascular Disease in Men and Women in the Lipid Research Clinics Study" examined Fitness vs. Fatness as potential cause of death in all cases but especially in deaths resulting from Cardiovascular Disease (CVD). The results and finding of this experiment will be examined on this page in order to discover the connection between fitness, fatness and the health issues that result.

In the 1990s, the prevalence of obesity nearly doubled in the United States making it a significant public health issue (Weinstein 10). During that decade, between 280,000 and 325,000 deaths per year were attributable to obesity. The American public spends billions of dollars on weight loss efforts annually, yet most Americans cannot reduce their weight or prevent weight gain with aging. Below is a graph depicting overweight and obesity trends in the United States (overweight, including obese = BMI>25; overweight, excluding obese = 25<BMI<30; obese = BMI>30):

Graph of overweight and obesity trends in the United States taken from "Joint Effects of Physical Activity and Body Weight on Diabetes and Cardiovascular disease," an article written by Amy R. Weinsten and Howard D. Sesso.

Research showing that fitness can reduce the impact of obesity on mortality and morbidity is of great public health importance. It is plausible that many persons who are not able to maintain a reduced weight could attain and maintain a higher level of fitness. If higher fitness levels in obese persons substantially reduced morbidity and mortality, this approach could provide improved health and longevity in these persons at increased risk. Furthermore, there have been indications that there would be a reduction in risk with greater physical activity; an improvement in cardiorespiratory fitness may be responsible for any reductions in the risk of disease. As such, increased physical activity could contribute to the reduction in diabetes and CVD risk.

EXPERIMENT:

Participants for this cohort study were gathered from eight different locations across the United States: Houston, Texas; Oklahoma City, Oklahoma; Palo Alto, California; La Jolla, California; Cincinatti, Ohio; Iowa City, Iowa; Minneapolis, Minnesota; and Seattle, Washington. Although the sample was taken from defined occupational, household, and school groups, the sample did not nessesarily reflect the people of those locations and groups. Despite the geographical diversity, not enough of a sample of minority persons were examined to make a separate study possible. In conducting this experiment, a two-stage initiation process was implemented. After a first short visit from each candidate at one the eight study centers, the final participants for the second visit were selected by randomly selecting 15% of all of the visit 1 participants including 100% of those found to have elevated plasma lipids. Fitness measurements for those involved were tak en during the second visit. Because heart rate was used in the experiment to represent fitness, participants on heart rate altering medicines, possible cardiovascular disease, or other miscellaneous contraindications were excluded from the test. All told, the experiment included 5366 participants: 2506 women and 2860 men.

Traditionally, there have been several problems in experiments of this nature involving the magnitude of the survey and a standardized way of measuring fitness and fatness. In this experiment, fatness was measured by measuring the Body Mass Index, or total weight in kilograms divided by height in meters squared. Fitness was assesed by measuring the time to produce a predicted maximal heartrate by using the Bruce Protocol. This protocol involves running the participant through seven three-minute stages in which the incline and the speed of the treadmill were gradually increased. The test was stopped when 90% maximal heart rate was reached or if the patient was unable to continue because of chest pain, fatigue, dyspnea, leg pain or abnormalities in the electrocardiogram. The level of personal physical fitness was also measured in the frequency of strenous exercise per week. Persons who exercised vigorously three or more times per week were catego rized as very active, those who exercised strenously less than three times per week were categorized as moderately active, and those who did not exercise at all were considered inactive. Smoking history of all participants was measured as well. Results were collected by annual follow-up calls to the cohort. By this method,the vital status of 99.6% of the participants were known. To ascertain the vital status of the remaining 0.4% of the study members the National Death Index and the Epidemiology Research Index were consulted.

Several statistical techniques were employed to analyze the data. "To account for the sampling scheme, we treated the data as a stratified random sample with two strata: hyperlipidemic persons and normolipidemic persons (including borderline hyperlipidemic persons).Because of the higher proportion of hyperlipidemic persons in the sample relative to the population, mortality rates were calculated by averaging the across the lipid strata using the inverse of the sampling probability as the weight. Associations between the body mass index and fitness and mortality were examined using stratified Cox proportional hazards models, with sampling strata (hyperlipidemic persons and normolipidemic persons) as the stratifying variable. These procedures enables us to draw inferences to those screed at visit 1. Statistically Analysis System software was used to conduct analyses." (American Journal of Epidemiology 833).

RESULTS:

There was a distinct difference in mean body weight between men and women. The mean body mass index in men (27.4kg/m2) not only is in the overweight range but, in addition, is significantly higher than that of women (24.9kg/m2). Overall, only 38% of men were in the normal weight range while 50% were overweight and 12% were obese. Women tended to be slightly less obese: 65% were normal weight, 23% were overweight, and 12% were overweight. Despite this, there was not an overwhelming correlation between body mass index and fitness with 7% of the women and 10% of the most fit quartile were obese. Although all cause mortality rates did not vary significantly across the first four body mass quintiles, there was a large increase in mortality rates in the highest body mass quintile. However, in the case of cardiovascular disease mortality, rates increased in a monotonic fashion from the lowest to the highest body mass quintile in both genders. Fitness had the opposite effect on mortality rates providing a steady decrease in rates from the lowest to the highest quintiles. Death rates for the highest body mass index quintile and the lowest fitness quintile were similar for all-cause mortality in women and men. This is true of cardiovascular disease mortality as well. The graphs below describe the hazard rates in men and women for both all-cause mortality and cardiovascular disease mortality based upon level of fitness and body mass index. In all cases, the hazard ratio of fit, non-fat individuals was set to 1.As expected mortality rates are the highest in obese, unfit individuals and lowest in fit individuals. In women, there was a drastic decrease in death rates between fat and non-fat unfit individuals. Although a similar pattern is common in males, it is far less pronounced. In addition, in all-cause mortality in women, fat but fit individuals did almost had almost a great of a chance as non-fit, non-fat individuals.

Relative hazard in women categorized by fitness level and body mass index adjusted for age, education, smoking, alcohol, and Keys score.

CONCLUSION:

The graphic shown below provides an overall indication of the affect of fitness and body weight on Cardiovascular disease and diabetes. However, it is our goal to highlight the growing argument between the relative health risks of fitness versus fatness and its affects on the health of the individual.

Joint effect of physical activity and body mass index on the risk of diabetes and cardiovascular disease taken from the article "The Joint Effects of Physical Activity and Body Weight on Diabetes and Cardiovascular Disease" by Amy R. Weinstein and Howard D. Sesso.

This research showed a correlation between the mortality rates in individuals exhibiting high levels of fatness and low levels of fitness. Both high levels of fatness and low levels of fitness tended to increase both all-cause mortality rates and mortality rates involving cardiovascular disease. Fitness proved to be a more accurate predictor of mortality rates than fatness; however, the difference could have been caused by the relatively high measurement precision in the fitness measurements versus the relatively low measurement precision in the fatness measurements. Either way, the benefits of being fit were found not to totally alleviate the risk of being fat or that being slender totally alleviated the health risks of being unfit. From this it is clear that the best way to avoid both all-cause and cardiovascular disease death is to be both fit and have a normal body weight.

Works Cited:

Stevens, June, et al. "Fitness and Fatness as Predictors of Mortality from All Causes and from Cardiovascular

Disease in Men and Women in the Lipid Research Clinics Study." American Journal of Epidemiology 19

June 2002: 832-41. Oxford Journals. 7 Nov. 2006 <aje.oxfordjournals.org>.

Weinstein, Amy R., and Howard D. Sesso. "Joint Effects of Physical Activity and Body Weight on Diabetes and

Cardiovascular Disease." Exercise and Sport Sciences Reviews Vol.34 2006: 10-15. American College of

Sports Medicine.

December 5, 2006 http://student.biology.arizona.edu/honors2006/group13/home13.html