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Which has a greater effect on a long and healthy life—body weight orphysical fitness? Is it possible, as one controversial school of thoughtsuggests, for an individual to be fat and fit?
The latest salvo in the fat-versusfit debate comes from a group ofinvestigators at Harvard Medical School. In the December 23, 2004, issue ofNew England Journal of Medicine, Frank Hu, MD, and colleaguesreported on a study of more than 116,000 participants in the Nurses' HealthStudy.1
When the study was established in 1976, baseline information was gatheredon the women, who were 30 to 55 years of age and free of known cardiovasculardisease and cancer. Mortality data from 24 years of follow-up were analyzed bycalculated body mass index (BMI) and self-reported levels of physicalactivity.
The findings by Hu's group suggest that physical activity is healthful, butdoes not eliminate the increased risk of death due to obesity. At every levelof physical activity, according to researchers, fatness predicted a higherrisk of death.
"The evidence is compelling that both obesity and a sedentarylifestyle are strong independent risk factors for premature death," saysco-author JoAnn Manson, MD, an endocrinologist at Brigham and Women's Hospitalin Boston. "We found an excess risk of death among the overweight [and]even more among the obese."
It's possible, Manson says, that fat itself exerts a harmful effect on thebody. Not just an inert material that accumulates around the hips, accordingto increasing evidence, fat is actively involved in metabolism and health bysecreting hormones, inflammatory factors, and growth factors.
CONFLICTING SCIENCE
Other experts suggest that the evidence is not so clear. Some contend thatit is not only possible to be fat and fit, but it may be healthier than beinglean and sedentary.
"Sure you can be fat and fit," says Tim Church, MD, MPH, PhD,vice president of research at Cooper Institute in Dallas. "Then again,it doesn't take much to be fit."
Cooper Institute has been one of the leading proponents of the fat-and-fithypothesis. Researchers from the center have published numerous paperssuggesting that cardiovascular fitness is a better predictor than obesity ofheart disease and cardiac-related death. Obese men who exercise regularly,according to Church, have a death rate only slightly higher than unfit men ofnormal weight.
Similar findings recently were reported by June Stevens, PhD, RD, andcolleagues at University of North Carolina, Chapel Hill. A study of fitnessand fatness among 1,359 Russian men and 1,716 American men aged 40–59years suggests that "the effects of fitness on mortality may be morerobust across populations than are the effects of fatness," theyreport.2
In the January 2004 issue of Diabetes Care, Church and colleaguesat Cooper Institute reported on a study involving the calculation of all-causedeath rates among 2,196 men with diabetes. When the rates were analyzed acrossvarious degrees of fitness and BMI, researchers reported finding a"steep inverse" relationship between fitness and mortality,independent ofBMI.3
"We showed that overweight or obese individuals with diabetes who arephysically fit are at lower risk of dying than those who are normal weight butunfit," says Church. "Fitness is a much better predictor ofmortality than fatness."
MATTERS OF DESIGN
Glenn A. Gaesser, PhD, exercise physiologist at University of Virginia inCharlottesville, says that the analysis by Hu's group is flawed, leading toerroneous conclusions. "They may have overstated their case againstoverweight," he says.
The Nurses' Health Study relied on self-reported physical activity and noton an objective measure of fitness, such as a standard treadmill test, hesays. In addition, Gaesser contends, the BMI data used for comparison datefrom the baseline period of 1976 and do not take into account changes that mayhave occurred since.
Further, the Harvard group did not consider the effect of "weightcycling" or the possible harmful effects of weight-loss drugs, hesays.
EXCESSIVE EMPHASIS
Some experts suggest that factors such as behavior are more important tofitness than BMI and other measures that may not accurately reflect health."There's way too much emphasis on BMIs," Gaesser says.
"This whole thing about fat and fit is not a black-and-white issue,because fitness is not a continuous variable," he says. "It's nota simple thing: You're fit or unfit, you're fat or not fat. It's possible tofind people clinically defined as overweight or obese, using BMI criteria, whoare essentially healthy and fit by the most commonly used criteria."
For example, at 6 feet 5 inches and 230 pounds, Indianapolis Coltsquarterback Peyton Manning has a BMI of 27, which is within the over-weightrange (and theoretically puts him at a greater risk of insulin resistance,diabetes, cardiovascular disease, impotence and other ailments), but few wouldconsider Manning unhealthy or unfit.
Such examples of athletes and celebrities whose height and weight fallwithin overweight BMI ranges are often cited by fat-acceptance advocates andthose who claim that the risks of obesity are overblown.
The fat-and-fit person is "an unusual situation," sayscardiologist Gerald Fletcher, MD, of the Mayo Clinic in Jacksonville, Fla."You might find it in athletes, individuals who are muscle-bound,wrestlers. People are hoping that there's a window of opportunity for them,and there isn't."
On the other hand, nobody argues that BMIs are meaningless. "Clearly,there's a level of fatness where no amount of fitness will compensate,"Church says.
Rather than focusing on an arguably arbitrary measure such as BMI,clinicians might serve patients better by addressing behaviors that lead tophysical fitness and improved health. Weight loss will inevitably follow.
"Obesity is a symptom of behavior, and that behavior is physicalinactivity and poor diet," says Church.
For the vast majority of Americans, weight loss by itself "is not aworthwhile objective," says Gaesser. "What is worthwhile is thebehavior that may lead to weight loss," he says. "We make amistake by putting so much emphasis on achieving a certain weight-loss goal.It's far easier to get a fat person fit than to get a fat personlean."
Manson agrees that increasing physical activity and fitness are worthygoals for patients. "It's hard to maintain overweight if you'rephysically fit," she says.
"Being physically active and fat is better than being fat andsedentary, but not as healthy as being lean and physically active," saysManson. 
References
2. Stevens J, Evenson KR, Thomas O, et al.: Association of fitness andfatness with mortality in Russian and American men in the lipids researchclinics study. Int J Obes Relat Metab Disord 28: 1463–1470, 2004.[Medline]
3. Church TS, Cheng YJ, Ernest CP, et al.: Exercise capacity and bodycomposition as predictors of mortality among men with diabetes.Diabetes Care 27:83–88, 2004.
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