what did steven blair mean when he stated in his article "in essence physical activity is the common denominator for the clinical treatment of low fitness and excess weight making the "fitness verse fatness" debate largely academic"? What did he say we should be focused on?
Transcribed Image Text: The Fitness, Obesity, and Health Equation
Is Physical Activity the Common Denominator?
Steven N. Blair, PED
ments are less prone to misclassification and because fac-
tors other than activity may influence both fitness and health
through related biological factors." For example, the age and
Tim S. Church, MD, MPH, PhD
HE MODERN LIVING ENVIRONMENT IN DEVELOPED COUN- examination ycar-adjusted relative risks for all-cause mor-
tries is characterized by low daily energy expendi- tality in 1263 men with type 2 diabetes are 1.8 for inactiv-
ture and an abundant and inexpensive food supply, ity but 2.9 for low fitness.
making positive energy balance common. The re-
sult is a rightward skewing of the body mass index (BMI) dis- rates of cardiovascular disease (CVD) or all-cause mortal-
tribution and an increasing prevalence of obesity.
Indisputable evidence links obesity to health problems, rates in the former group are about one half those of the lat-
including risk of cardiovascular disease, type 2 diabetes, some ter." These results are similar whether BMI, percent
cancers, and all-cause mortality.' These associations are dose- fat, body fat mass, or waist circumference is used as the body
related, temporally consistent, and biologically plausible, habitus measure" and are consistent for women and men"
which support a causal hypothesis. Physical inactivity also and for men with type 2 diabetes." These results also per-
has a dose-related, temporally consistent, and biologically tain to nonsmokers and after exclusion of individuals with
plausible relationship to the same health outcomes as those chronic disease or deaths within the first 5 years of follow-
as for obesity, and both obesity and inactivity have similar up." Moreover, 150 minutes a week of moderate intensity
patterns of association with clinical risk indicators such as physical activity is sufficient to avoid the low-fitness cat-
blood pressure, fasting plasma glucose, and inflammatory egory. These results are consistent with those reported in
markers." Furthermore, declines in average daily energy 24 studies identified in a systematic review on physical ac-
expenditure are a likely underlying caufe of the obesity tivity, CRF, obesity, and health."
epidemic."
However, the majority of studies examining obesity and as predictors of health outcomes, with somewhat divergent
health have not adequately accounted for physical activity. results.s Wessel and colleagues“ report that women with
When physical activity has been considered, investigators low self-reported functional ability had higher risks of CVD
have often relied on simple self-report questionnaires in outcomes than women with higher levels of fitness. In con-
which inaccuracy can increase proportionally with the re- trast, BMI and fat distribution were not associated with CVD
spondent's weight. Failure to adequately quantify physical risk. These findings are consistent with studies showing that
activity when examining the risks of obesity is similar to ex- adequate levels of activity or fitness confer health benefits for
ploring risk factors for cancer and misclassifying tobacco women and men in normal-weight, overweight, and obese
use. Physical activity and weight are closely linked and each categories.D In contrast, Weinstein and colleagues" re-
must be measured accurately and considered carefully when port that BMI is stronger than physical activity in predicting
examining the other.
Previous investigations, including studies from our group, effect on the relation of BMI to diabetes. They report signifi-
have examined the individual and joint associations of car- cant inverse gradients of risk across categories of physical ac-
diorespiratory fitness (CRF) and body habitus to health out- tivity for 3 different methods of assessing activity although
comes. Use of maximal exercise tests to quantify CRF pro- the associations became nonsignificant after adjustment for
vides an objective evaluation of an individual's recent activity BMI in 2 of the 3 analyses.
patterns and accounts for 70% to 80% of the variance in de-
tailed activity records.' Cardiorespiratory fitness is stron- are why is the association between physical activity and in-
ger than self-reported physical activity as a predictor of many cident diabetes substantially reduced when adjusted for BMI
health outcotnes, most likely because fitness measure-
Obese individuals with at least moderate CRF have lower
ity than their normal-weight but unfit peers, In fact, death
Two reports in this issue of JAMA examine activity and BMI
incident type 2 diabetes and that physical activity has little
Key questions raised by the 2 articles in this issue of JAMA
as reported by Weinstein et al" and why is there litle evi-
Transcribed Image Text: dence of a protective effect for activity in overweight or obese maintenance. In essence, physical activity is the common
women? And, conversely, why do Wessel et al" observe a
substantially lower risk for adverse CVD events in obese and
nonobese physically active women yet no association be- academic. Thus, physicians, researchers, and policymak-
tween body habitus and CVD outcomes?
Differences between these 2 studies, as well as the differ-
ence between the findings of Weinstein et al and other pub- how to get sedentary individuals to become active. With 40
lished work on this topic, may be due to differences among
study populations, methods, and outcomes. Wessel et al taining the recommended amount of daily physical activ-
followed-up women with clinical indications for coronary ity motivating the individuals to incorporate physical ac-
angiography, whereas Weinstein et al" followed-up appar- tivity into their daily lives, whether to lose weight or reduce
ently healthy women in the health care profession. Al-
though related, study outcomes also differed-adverse CVD nancial benefits at an individual and societal level.
events" and type 2 diabetes." Valid assessment of habitual
physical activity is difficult. Wessel et al" used 2 measure- physical activity has health benefits at any weight, and for
ments-an estimate of CRF by the Duke Activity Status In- those who want or need to lose weight, physical activity is
dex." which was previously validated against maximal
oxygen uptake, and a self-reported physical activity ques- sequently.physical activity promotion should be a founda-
tionnaire. Their results for Duke Activity Status Index are
similar to other findings for objectively measured cardio-
respiratory fitness and mortality, as were their results nity needs to lead in communicating the importance of physi-
when using the self-reported questionnaire. The 2 studies cal activity for health and weight maintenance. Just as weight
used different measures of sel-reported physical activity: is addressed in some manner at nearly every physician visit,
therefore, it is possible that the one used by Wessel et al is so should attention be given to recommending the accu-
more accurate than the one used by Weinstein et al, high- mulation of 30 minutes a day of moderate intensity physi-
lighting another difference in the 2 studies. The question- cal activity at least 5 days of the week. This can be obtained
naire used by Weinstein et al" has acceptable reliability and through brisk walking, bicycling, swimming, or activities
shows modest correlations with other self-reported physi- of daily life such as housework or gardening.
cal activity measures but apparently has not been validated
with a gold standard, such as maximal oxygen uptake ordou-
bly labeled water, as was the case for Duke Activity Status Adnoeledgment We thank Miton Z Nichaman, MO. SD, and Michael LaMonte
Index." There are other differences in methods. Wessel et b, MPH for helptul comements on an earler draft of this editorial. and Melbe
al" and other recent studies"D obtained baseline data at
a clinical examination, whereas Weinstein et al" did not have
such information. This may have led to greater misclassi-
fication for some variables such as the likelibood of detect-
ing subclinical discase, which could result in health status
influencing the combined associations among activity, BMI,
and incident disease.
The findings of Wessel et al" and Weinstein et al" pro-
vide a timely opportunity to examine an ongoing debate and
offer a resolution The results presented by Weinstein et al
suggest that increased BMI is substantially more important in the obese. Med Si Sports kae. 1915624-0
for incident diabetes, and Wessel et al" suggest that inac-
tivity or low fitness is a greater threat to health in terms of
CVD outcomes In recent years, the "fitness vs fatness" is-
sue has led to controversy and heated debate. Although the oent evidente and resarch e ed So Sporti.bei n1
debate may never be fully resolved, the relative contribu-
tion of fitness and obesity to overall health and risk actu-
ally may be a trivial matter because a common treatment is
already available for both low fitnessand excess body weight.
Increasing regular physical activity results in predictable in-
creases in fitness, and it is widely accepted that regular physi-
cal activity is a core component of successful weight los
programs and, more importantly, of long-term weight loss
denominator for the clinical treatment of low fitness and ex-
cess weight, making the "fitness vs fatness" debate largely
ers should spend less energy debating the relative health im-
portance of fitness and obesity and more time focusing on
to 50 million adults in the United States currently not ob-
risk of chronic disease, will have substantial health and fi-
In summary, the majority of studies show that regular
a critical component of long-term weight management. Con-
tion of clinical therapy and public health policy, whether
to promote health or weight control. The medical commu-
Funding/Support This works sapported by grants ACDD6945, HLD6622, and
HLO7S442 from the National institites of Heath
Monow, MA for editonal atance
REFERENCES
1. National Institutes of Health, Nabonal Hearn, Lung and ood intitute. Clini-
cal Guidelines on the fdentificabon Evaluatan and Treatment of Ovenweieht
and Obeutyin Adu: The Evidence Report. Rockvile. Md. National insttuter of
Hedth, National art, Lung and alood insttute, t998.1-225.
2. Pysical Ativity and Healte A Report of the Surgean Genetal Allarta, CGa
USDept of Health and Huan Services, Centeri for Dieae Controland Preven-
tion, NationalCenter for ChronicOaePrevenbonand Health Promoton 1956
2. Chuch TS, Barlow CE. tamest CP. et at Asociations betwien
tory ses and Cireactive protein in men Arterioscder Thromb Vasc Bol. 2002
22:19-T876.
A Fagard RH Physical actvity in the prevenbonand tralment al bypertendon
rdiotespire-
5. We M Gbbons LW, Mdhell TL et al he ocation bcheem cndore
patory nes andmpaed fating dutose and type 2dabetes melitus in men
A hitern Med 199913039-96
6 H JO, Melanon Ovevirw of the determiriant of overeight and obe
7 Pattenbarger RS Ma SN, LeeM, Hyde RT. Meueent of physcl ac
tiity to aest hath effects in free-lying populatione Msoport t 19
2560-20
EHar SN Cheng Y, Holder S. phyical activity or phyica mo inh
potantin defining health benets7 Med SeSpoiti ba 200 79-5399
SWe M. Ceons LW Kanget
fory fitrestand ohyscal inacvity a
dubeles Ann ten Aled 2000,1260S-6.
Nehanan MZ MN
redcton of inotaity in men with type 2
hpert
Parlove Ctet l Rtionshp between
10. Wel M
pratory
1999.2801542a553