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Review Article
Obesity, diet, exercise and weight control— a current review
M. K. Chin,Archie Y. S. Lo, X. H. Li, Mimi Y. M. Sham an d Yvonne W. Y. Yuan
Abstract
Obesity can be attributed to complex physiological, genetic, cultural and psychological factors. Itshould not be regarded merely as a result of weak will power or other character deficits. Thispaper attempts to provide background information on energy balance which is important vis-a-vis weight control. Weight reduction as a desirable end-point of negative energy balance is best
achieved through a combination of dietary restriction and exercise. Two alternative methods ofweight reduction are proposed and discussed. Nutritional, behavioural changes and carefulmonitoring of exercise and diet should be implemented holistically to ensure a successful weightreduction programme. Individuals also need to be aware of the many myths and misconceptionssurrounding weight control.
Keywords: Obesity; Diet; Exercise; Weight control
Introduction
Despite a growing awareness of the detrimental ef -fects of excessive body fat on health, obesity remainsa major public health problem among many Westernsocieties, and more recently, in Asian countries aswell. It has been estimated that at least 20% of theadult population in the United States are overweight,with this figure increasing to 35%-40% in adults over40 years old.
1 In a National Heart Foundation studyon Australian men and women over the age of 45,60% an d 50%, respectively, were considered over-weight.
2In a recent survey of school children in Beijing,
Sports Science Department, Hong Kong Sports Institute, Sha Tin, HongKongM. K . Chin, PhD,Mimi Y. M. Sham, BSc, Dipl Dietetics
Hong Kong Heart Centre, 40 Stubbs Road, Hong KongArchie Y. S. Lo, MD (Chicago), FRCPCDepar tment of Physiology, University of Cambridge, Downing Street,Cambridge, CB2 3EG, United KingdomX . H. Li, MDHong Kong Centre of Sports Medicine and Sports Science, The ChineseUniversity of Hong Kong, Sha Tin, Hong KongYvonne W.Y . Yuan, M ScCorrespondence to: Dr M. K. Chin
3%-5% of the children had body weight in excessof20% over the recommended range.
3Comprehensive
data are not available on obesity in the Hong Kongpopulation, but the frequency an d variety of com-mercial advertisements pertaining to weight reductionprog rammes indicate that there is strong interest inthis issue. The objective of this paper is to present thescientifically verifiable facts on diet, exercise an dweight control in relation to obesity, as opposed tosundry popular myths and misconceptions.
Definition of obesity
Obesity can be broadly defined as an excessive en -largement of the body's fa t stores. Total body fa texists in one of two forms: essential or storage fat.Essential fat is necessary fo r normal physiologicalfunctions, and can be found in varying degrees in allorgans including the central nervous system. Storagefat is deposited in the adipose tissue throughout thebody mainly under the skin. Adipose tissue serves asan efficient means of insulation and fuel storage.
Th e amount of essential fat in a person remainsfairly constant; it is primarily storage fa t that is affected
by diet or exercise.
181
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182 J Hong Kong Med Assoc Vol. 44, No. 3, September 1992
While no universally accepted def ini t ion fo r obes-
it y exists, there is a general consensus tha t tota l body
f a t levels above 20% and 30% for m en and women,
respectively, would constitute obesity.4
Th e hea l th
consequences associated with obesity are numerous,
including hypertension, hypercholesterolaemia,
hyper t r ig lycer idaemia , non-insulin-dependent dia-
betes mellitus, gallstone disease (cholelithiasis), and
several forms of cancer.5
Men and women should
strive to maintain total body fa t levels at about15 %
and 25%, respectively.Obesity can also be understood in terms of the
'body mass index' (BMI). This index is der ived by
div iding body weight (W) in kilograms by he ight
squared (H2) in metres ( B M I = W/H
2). The health risk.s
associated with obesity progressively increase as the
BMI exceeds 30.6
Being above a v e r a g e weight does
no t necessarily imply that a person is too fat. Eli te
athletes and body builders have increased musclemass which, produces a raised BM I in the 'overweight'
range, but such persons do not have any abnormal
increase in body fat. Therefore, th e interpretation of
th e B M I must be carried out judiciously.
Types of obesity
There are two major categoriesof obesity: hyperplastic
and hypertrophic obesity, Hyperplastic obesity re -
sults from excess calor ic intake during critical periods
(the last trimester of pregnancy, adolescence and in-
fancy) resulting in the formation of addi t iona l fa tcells. Hypertrophic obesity is caused, by the formation
of excessively large fa t cells as a result of excess caloric
in take . This latter form is characteristic of adult-onset
obesity. It appears that once adulthood is attained,
the number of fat cells (adipocytes) is constant, The
adipocytes do not increase or decrease in number
under normal conditions; they merely expand or con-
tract.7
Obese individuals who lose weight tend to
gain it back quickly because th e abundant adipocytes
are available as vacant storage sites.
Childhood obesity
A n i m a l and human studies have demonstrated that
genetic factors can contribute to obesity. The inci-
dence of obesity in children is about 7% in those with
two lean, parents, 40% in those with one obese parent
and 80% in those with two obese parents.8
Further,
chi ldhood obesity is a significant risk factor for adult
obesity.9
Infan ts are often overfed, partly because
parents misinterprets the signals. A baby may cry
because he is wet, restless, hot, cold or lonely. It is a
common response, however, lor parents to assume
tha t the baby is hungry and hasten to feed him.
Childhood ea t ing
pe rmanen t . If poo
tha t obesitywill de
mot iv a t ed person
ha b i t s of a l i f e t i m e
Body fa t
People come in all shapes and sizes. B o d y composi-
t ion and fat d i s t r ibu t ion are s t rongly inf luenced by-
genetics, age and gender. A b d o m i n a l obesity, t yp i ca l
in men, tends to result in persons w i th 'apple' shapes.
A peripheral fa t pattern w i t h extra fat on the hips and
thighs, more commonly seen in women, resu l t s in
'pear' shapes. People a re most commonly c lassi f ied
a s 'apples' o r 'pears' using the w a i s t - t o - h i p ra t io
( WHR) . WHR is a ra tio of the c i r c umfe r enc e s at these
tw o locations, and compares f a v ou r a b ly w i th com-puted tomography of the abdominal a r e a .
l 0The WHR
reveals not only th e relative distribution of abdomi-
nal to glu tea l - femora l fat, but also th e qua n t i t y of
in t ra-abdominal o r visceral fat. Men are cons idered
upper-body obese when the WHR is greater t h a n0.95
and in women, when it exceeds 0.85." There is in-
creas ing evidence to indicate t ha t abdominal obesity
is , more so than to ta l body obesity, a serious risk
fac to r fo r coronary a r t e ry disease,11
Excess abdo mina l
f a t accelerates th e rate o f coronary artery disease in
three ways , it increases blood cholesterol levels, raises
blood pressure and decreases th e body's abi l i t y to
u se insulin effect ively, l e a d ing to i n su l in res is tance.12
Abdominal fat is, however, hyperactive, and re-
sponds well to weight reduction. This means that
abdominal fa t levels may be reduced with even a
modest reduction in body weight On the o the r hand,
fa t in the cells on the hips and thighs of females are
difficult to lose. In fact , research suggests that glu tea l -
f emora l fa t cells cling to their fa t except dur ing
lactation. 13
Energy balance-
expenditure
-intake versus
Energy balance is the relationship between energy
i n t ake and energy expenditure. When this balance is
positive, th e extra calories are stored as fa t , W h e n this
ba lance is negative, storage fat is metabolized to pro-
vide fo r energy needs. If the number of calor ies
ingested corresponds to tha t consumed in metabo-
lism, body weight does no t change except for a sma l l
intra-day variation (± 1 kg), which is mainly due to
f luc tua t ions in the body's water content. M a n y com-
plex factors affect th e rates of energy ingestion, and
caloric expenditure through exercise and metabol ic
needs.
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Chin et al.: Obesity, exercise andweight control 183
Energy intake
Quanti ty
Obesity has classically been regard ed as a problem ofdisordered eating habits. Most surveys of energy in-
take, however, show tha t in general, obese individu alsdo not consume more calories than lean individu-als.
14A recent study
15of 107 males and 109 females
ranging in age from 18 to 71 years, showed that thedaily energy intakes of lean and obese adults wereidentical when expressed as kJ-kg
-1lean body weight.
Lean individuals actua lly consum ed m ore energy than
obese individuals when daily caloric intake was ex-pressed as kJ-kg
-1total body weight.
Diet compositionNutritionists previously thought that a calorie was acalorie, but we know no w that not all calories are thesame. A forced feeding study showed that prisonersona high fa t diet gained weight m ore easily than those ona low fat, high c arbo hydrate diet.
16Researchers in this
study cited two probable mechanisms for this observa-tion. Firstly, extra fa t calories co ntribute m ore to bodyf a t because dietary fat is converted to stored fa t with97% efficiency. Carbohydrates from a meal, in contrast,are converted to body fa t with only 77% efficiency.
There is, therefore, an eightfold difference in the amount
of energy wasted. Secondly, the metabolic rate followinga meal (thermic effect of a meal) is m uch higher whenthe meal is high in carbohydrates than when it is high infat. Calories expended in this way contribute to dailyenergy expenditure, rather than to increasing fa t stores.The relationships linking diet com position, energy intakeand body fat are illustrated by another study of 216adult men and women.
15The obese derived a greater
portion of their daily energy intake from fa t when com-pared w ith the lean. Therefore, one should aim for energyintake from a high carbohydrate, low fat diet, as dietcomposition m ay be as im portant as diet energy content
in the reduction ofobesity.
A comparison of a typicalChinese m enu with a low fat, high c arbohydrate samplemenu is illustrated in Table 1.
Caloric restriction
For a long time, caloric restriction has been regardedas the cornerstone of weight-loss regimens. Numer-ous low and ve ry low calorie diets have beenintroduced for the treatment of obesity.
17However,
energy-reduced dieting may not be the best weight-loss thera py because of the m any problems associatedwith reduced energy consumption. Firstly, severe re-
striction in energy intak e reduces the basal metabolicrate (BMR) by as m u c h as 30% . This m ay shift theenergy balance back in the direction of energy stor-
Table 1. Typical one day Chinese menu and isocaloric
modified low-fat, high carbohydrate diet.
Regular diet(44% of energy as fat)
Low-fat,
high carbohydrate diet(20% of energy as fat)
Breakfast
Bread: 1 slice
Margarine: 1 tbsp
Whole milk: 1/2 cup
Lunch
Stir fried chicken noodleChicken with skin: 3.5 oz
Cooking oil: 1.5 tsp
Bamboo shoot: 1/2 cup
Egg noodles: 1 cupChinese tea
Snack
Peanuts: 1/2 oz
Dinner
Stir fried marbled porkwith pineapple
Pork chop(lean and fat): 3 oz
Cooking oil: 1.5 tsp
Pineapple: 1/2 cup
Rice: 1 cupOrange: 1
Breakfast
Bread: 2 slicesJam: 1tbspSkim milk: 1 cup
Lunch
Chicken noodle in soupChicken breast: 3.5 oz
Cooking oil: 1 tsp
Corn: 1/2 cup
Egg noodles: 1 cup
Chinese tea
Snack
Crackers: 4 pieces
Dinner
Stir fried lean pork
with pineapplePork chop (lean): 3 oz
Cooking oil: 1.5 tsp
Pineapple: 1/2 cup
Rice: 2 cupsOrange: 1
age.18, 19
Since BMR accounts for 70% of total daily
expenditure, this reduction in B MR is a significantdifference. This B MR reduction m ay account in partfor the 'plateau' reached by mo st dieters when weightloss slows an d stops even when caloric intake re -m ains stable. Secondly, as much as 25% of the weightlost by dieting alone can have come from lean bodymass (LBM).
20This loss of LBM is potentially danger-
ous if the body depletes protein reserves in essentialareas of the body. The percentage of LBM lost de-creases w hen exercise is com bined with diet. Thirdly,the energy c onservation process resulting from severedieting can persist even after the dieting period isover. This causes body w eight to be regained rapidlyuntil it reaches the pre-dieting level.
21Studies in ani-
mals and humans have shown that when theserepeated cycles of weight gain and loss occur, subse-quent weight loss can be made more difficult.
22
Research ha s also shown tha t when weight is regainedafter dieting, muscle tissue tends to be replaced byfat. This has also been confirmed in a current studyon diet m anipulation in rats.
23
Energy expenditure
In the past, the focus of both health professionals an dobese individuals has been on energy intake . Research
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184 J Hong Kong Me d Assoc Vol. 44. No,
has, however, increasingly demonstrated tha t the key
to effect ive therapy is to work on the expenditure
side of the equation. The average daily energy ex-
penditure in individuals between th e ages of 23 and
50 is 2,700 kcal for men and 2,100 kca l fo r women.24
Total energy expenditure is determined by three m a-
jo r components, viz. the BMR (70%), thermic effects
of food (10%) and exercise (20%). In the previous tw o
sections, we addressed th e issues of diet composition
in relation to the thermic effect of food, and diet re -
strict ion in relation t o BM R in the energy e x p e n d i t u r e
equation. In the following section, we will focus on
th e thermic effect of exercise.
C O .
50
48
46 - i
Exercise and weight control
In human beings of al l ages, inac t iv i ty ha s been asso-
ciated with obesity.25, 26
Th e addition of an exercisecomponent in a weight loss regimen appeared to im-
prove th e outcome, both init ia lly and in the long
term, by increasing th e total energy output and af-
fecting substrate utilization.2
(i ) Energy output
Exercise affects energy output in several ways.
The most obvious way is via the thermic response
to acute exercise, th e magnitude of which is de-
t e rm ined by the mode, intensity and durationof
the exercise.
27
The guidelines suggested by theAmer ican College of Sports Medicine28
state that
th e 'minimal threshold' of exercise training for
weight and fa t reduction includes continuous ex-
ercise of at least 20 to 30 minutes duration, at
moderate exercise intensity (60%~70% of maximal
heart rate) sufficient to spend 300 or more kcal
per session, with an exercise f r equency of at least
three days per week. Significant elevations in
resting energy expenditure have also been ob-
served in the post-exercise recovery period.29
A
systematic study30
on the metabolic after-effects
of exercise indicated that the resting metabolic
rate ranged f rom 7.5% to 28% higher f ou r hours
af ter exercise compared with a control day in
which no exercise was taken. The higher metabolic
rate persisted for six hours and returned to base-
line levels after eight hours as shown in Figure 1.
The investigators calculated that this elevated
post-exercise metabolism (about 40 to 50 kcal),
over and above the energy cost of the exercise
bout i tself, would result in a reduced caloric
equivalent of about 2 kg a year if individuals
exercised daily. It appears that exercise is benefi-
cial in the control of body weight, not only for the
energy loss incurred during exercise, but also be-cause a considerable additional caloric
expenditure may occur post-exercise.
Hours After Exercise
Hours After Exercise
Fig. 1, Top, BM R af ter a vigourous exercise session
compared with non-exercise control day; bottom,
BM R ranged from 6% to 17% higher after a vigorousexercise session than if was at the same time of theday on non-exercise control days. The higher BMR
lasted six hours after exercise. Modified from de
Vries andGray.30
(i i ) Subst ra te u t i l i z a t i o n
Mild to moderate in tens i fy exercise is e f fec t ive
fo r weight reduction because of the increased
utilization of free f a t t y ac ids .31
Energy for short
periodsof high intensity exercise is derived a lmost
entirely f rom stored carbohydrates in the l iver
and muscles. Mild to moderate intensity act ivi t ies
of longer duration use both carbohydrate and fat
(Fig. 2).32
These data highlight th e importance ofth e 'long slow distance' concept when ta rge t ing
body fat as the energy substrate during exercise.
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Chin et al.: Obesity, exercise and weight control 185
•o100-01a >
3
„ 80-
2
•?.£t __
Ji 60 -(O
OTJ
S 40-
£"5e 20-O
oa° 0 •
_OM Fats ^o Table 2. Compariso\<^ weight.3
""""O n Carbohydrate y^a
•fj
/^^ BOlimuiii«m"" Variable
..a*"" "" CardiovascularO*** i andpulmonary
^W function
^ Nutritional\ deficiency
Tv.
^^w^ Lean body weight
\j
aRest 20 40 60 80 100 Level of HDL-C
% of ma ximum ox yge n uptake Sensitivity of insulin
Thermic effectFig. 2. Relative contribution of fat and carbohydrate as a
funct ion of exercise intensity, expressed as a Physiological and
percentage of the maximal oxygen uptake (VO 2 max). psychological stateModified from Astrand and Rodahl.32
Physical strength
Side-effect
Exercise and diet
, .. , . . , . ,. , ., , Plan of osingA negative energy balance is best achieved througha weight
combination of dietary restriction and exercise. A
n of different approaches of losing
Losing weight
only by severelimitationof
energy intake
Decrease
Occurs easily
Decrease
Decrease
?
Decrease
Under greatpressure
Decrease
Metabolic
disorder
Difficult to
maintain
Losing weight
by exercise andslight limitation
of energy intake
Increase
Generallydoes not occur
Increase or
unchanged
Increase
Increase
Increase orunchanged
Improved
Increase
Generallynone
Easy to
maintain
convenient means to partit ion a 500 k ca l/da y (3,500kcal/week) energy deficit is to reduce energy intake
by 250 kca l /day and increase energy expenditure by250 kca l /day . It is relatively easy to identify food
i tems that can be eliminated or reduced to provide a250 kc a l /day r educt ion in intake. A caloric deficit of3,500 kca l /week is equivalent to 0.5 kg weight loss.
A comparison of two alternative methods of weightreduction is i l lustrated in Table 2.
3B y com bining diet
and exercise, it is possible to achieve a deficit of 1,000calories/day, which is equivalent to approximate ly 1
kg of fat loss per week. While this m ay appear to bethe slow approach to weight loss, it is the most sensi-ble appro ach. Losses of lean body mass are minimal ,and fat loss so attained is more likely to be o f a per-
manent nature.33
Myths an d misconceptions of diet,exercise and weight control
With the increased popularity of exercise, obese indi-viduals are often confronted with exercise m yths andmisconceptions, along with gimmicks that are pro-moted as 'miracle agents' to assist in weight reduction.
Exercise and appetite
A common misconception of exercise in weight controlis that physical activity stimulates appetite, and the
resulting increased caloric intake negates the caloricexpenditure of the exercise itself. Although it is truethat increased food intake generally parallels increasedphysical activity, this relationship appears to holdonly with respect to normal act iv ity .
In a classical study,34
rats which w ere exercised dailyfor up to one hour showed a decrease in food intake andbody weight when com pared to sedentary control ani-mals. When he exercise duration wa s increased beyondone hour, food intake was increased bu t only to theextent that body weight was maintained. In contrast, atexhaustive levels of exercise (i.e. six hours), both bo dyweight and food intake decreased. The results of this
classical experimentare shown in Figure 3. Longitudinalphysical conditioning studies in hum ans also show nochange in calorie intake with m ild to m oderate intensityexercise training.
35
Rapid weight loss
Most rapid weight loss diets have one feature in com-m o n — t h e y a l low only a m o d e s t i n t a k e o fcarbohydrates . Carbohydrates const i tute approxi-m a t e l y 6 0 % o f a nor m a l m ix e d d i e t . Wh e ncarbohydrates m a k e up 10% or less of the diet, in
addition to an overall reduction in food intake, thebody starts to utilize its own carbohydrate stores in
the liver an d muscles. Since 3 g of water are stored
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188J Hong Kong Med Assoc V o l .
Conclus ion
recently, among A :
as well.The associated health risks an d diseases present
a tremendous dra in to the economy and a f f e c t th e quality
of life. Obesity can be a t t r ibu t ed to complex physiologi-c a l , genetic,cultural and psychological factors. It should
y as a result of weak will power
2 4 6 8 1 0
Duration of exercise (hours)
ts . Th e most effect ive programmes fo r
losing and mainta ining a desirable body weigh t incor-
porate restrictions in calor ic intake, and increases in
caloric expenditure through exercise. Nutri t ion, behav-
ioural changes, and careful moni to r ing o f exercise and
diet should be implemented holistically to ensure a
F i g . 3. R e l a t i o n s h i p b e t w e e n food i n t a k e , e n e r g y successful weight reduction, programme. Individualsexpenditure an d body weight in laboratory rats. A, need to be aware of the many myths and misconceptionssedentary zone; B, range of proportional response surrounding weight control Most 'mi racle agents' fo r(normal activity); C , exhaustion zone. M o d i f ie d f r o m " . , ' , , *T,' • ' J r •
Mayer etal. 34 weightlossdo not haveascientificbasis.
along with 1 g of carbohydrate f rom the body stores,
there is a substantial loss of body water along withthe depletion in the stores of carbohydrates. Thus,
weight loss in. the first few weeks of dieting is essen-
tially loss of body fluid, not body fat Rapid weight
loss diets so often fail because once a desired weightis achieved, the individual typically returns to a nor-
m al diet which is high in carbohydrates. The waterlost during the diet period is rapidly regained, oftenin a matter of days. Thus, the individual's weight
l i teral ly jumps back to its previous level, and the diet
is considered a failure.
Spot reduction
Spot reduction is the attempt to reduce fat in a local-ized area of the body through exercise. It is true thatvigorous exercise and. caloric restriction will cause ageneral reduction in body fa t stores. There is , how-
ever, no conclusive scientific evidence that exercise,
massage, sauna, special skin creams, body wrappings
or pseudo-electric devices will break up or reduce fat
deposits located in specific regions, in a study com-paring th e subcutaneous tat of the act ive (playing)
and inactive arms of elite tennis players, skinfold
Acknowledgements
The authors would like to thank M r Dennis Whitby
for his valuable suggestions to the manuscript and
Miss Queenie Tam for her clerical support.
References
1. Miller W J, Stephens T, The prevalence of ove rwe igh t
and obesity in Britain, Canada and United States.A m J
Public Health 1987; 77: 38-41,2. National Heart Foundation o f Aus t r a l i a R i s k Factor
Prevalence Study, Survey no. 3. 1989, Canberra:NHFof Australia an d A u s t r a l i a n Ins t i t u t e of Heal th , 1990:47-103,
3. Chen JD , Chao G H Exercisean d weight cont rol . Chin 1
Sports Med, 1989; 8: 167-72.4 . Leon AS, The role of physical activity in the prevent ion
and management of obesity. In : Rya n AJ , Al lm an FL J r,
eds. Sports medicine. 2nd ed. San Diego: A c a d e m i c
Press, 1989: 593-617,5. Bray G A . Effects of obesity on health an d happiness.
In : Brownell K D, Foreyt JP , eds. Handbook of eat ingdisorders: physiology, psychology, and t r e a tmen t o fobesity, anorexia, and bulimia.New York : Basic Books
I n c . , 1986: 3-44.6 . Miles DS. Weight control an d exercise. Clin SportsMed
1991; 10: 157-69,
8/14/2019 Obesity, Diet, Exercise and Weight Control
http://slidepdf.com/reader/full/obesity-diet-exercise-and-weight-control 7/7
Chin et al.: Obesity, exercise an d weight control 187
7. Hager A, Sjostrom L, Arvidsson B, et al. Body fat andadipose tissue cellularity in infants: a longitudinalstudy. Metabolism 1977; 26:607-14.
8. Mirkin G. Getting thin. Boston: Little, Brown & Com-pany, 1983: 79-80.
9. National Institutes of Health Consensus DevelopmentPanel on the Health Implications of Obesity. Healthimplications of obesity. Ann Intern Med 1985; 103:147-
51.10. Peiris AN, Hennes MI, Evans DJ, et al. Relationship of
anthropometric measurementsof body fat distributionto metabolic profile in premenopausal women. ActaMed Scand Suppl 1987; 723: 179-88.
11. Kaplan NM. The deadly quartet: upper-body obesity,glucose intolerance, hypertriglyceridemia, and hyper-tension. Arch Intern Med 1989; 149: 1514-20.
12. Stamford B .Apples and Pears—whereyo u 'wear' yourfat can affect your health. Phys Sportsmed 1991; 19:
123-4.
13 . Rebuffe-Scr ive M, Enk L, Crona N, et al. Fat cell m e-
tabolism in d i f f e r en t regions in w o m e n — e f fe c t ofmenstrual cycle, pregnancy, an d lactation. J Clin Invest1985; 75: 1973-6.
14 . Dreon DM, Frey-Hewitt B , Ellsworth N, Williams PT ,Terry RB, Wood PD. Dietary fat: carbohydrate ratioan d obesity in middle-aged men. A m J Clin Nutr 1988;47: 995-1000.
15 . Mil ler WC, Linderman AK, Wallace J, NiederpruemM. Diet composition, energy intake, and exercise inre la t ion to body fatness in men and women. A m J ClinN ut r 1990; 52:426-30.
16 . Danforth E. Diet and obesity. Am J Clin Nutr 1985; 41:
11-32.17 . Atkinson RL. Low and very lowcalorie diets. Med Clin
North Am 1989; 73:203-15.
18. Bray GA. Effect of caloric restriction on energy ex -penditure in obese patients. Lancet 1969; ii:397-8.
19 . Elliot DL, Goldberg L, Kuehl K S, Bennett WM. Sus-tained depression of the resting metabolic ratio aftermassive weight loss. Am JClin Nutr 1989; 49: 93-6.
20. Zuti NB, Golding IA. Comparing diet and exercise as
weight reduction tools. Phys Sportsmed 1976; 4:49-55.21. Jen KL. Effects of diet composition of food intake and
carcass composition in rats. Physiol Behav 1988; 42:
551-6.22. Brownell KD, Greenwood MRC, Stellar E, et al. The
effects of repeated cycles of weight loss an d regain inrats. Physiol Behav 1986; 38: 459-64.
23 . Dulloo A G , Girardier L. Adaptive changes in energyexpenditure during refeeding following a low-calorieintake: evidence for a specific metabolic component
favoring fa t storage. Am J Clin Nutr 1990; 52 : 415-20.24 . Katch FI , McArdle WD . Nutrition, weight control an dexercise. 3rd ed. Philadelphia: Lea & Febiger, 1988:108-9.
25 . Rose HE, Mayer J. Activity, calorie intake, fa t storageand the energy balance of infants. Pediatrics 1969; 41:
18-29.26 . Curtis DE, Bradfield R B .Long-term energy intake an d
expenditure of obese housewives. Am J Clin Nutr 1971;24 : 1410-7.
27 . Epstein LA, Wing RR. Aerobic exercise and weight.Addict Behav 1980; 5: 371-88.
28. American CollegeofSports Medicine. Resource manualfo r guidelines fo r exercise testing and prescription.Philadelp hia: Lea & Febiger, 1988: 355-61.
29 . Lawson S, WebsterJD , Pacy PJ , Garrow JS . Effect of a10 week aerobic exercise programme on metabolic ra te,body composition and fitness in lean sedentary fe-
males . Br J Clin Pract 1987; 41: 684-8.30. de Vries HA, Gray DE. After effects of exercise upon
resting metabolic rate.Res Q Exerc Sport 1963; 34 :314-21.31 . Girandola RN. Body composition change in women:
effects of high and low exercise intensity. Arch PhysMe d Rehabil 1976; 57 : 297-300.
32 . Astrand PO , Rodahl K . Textbook of work physiology.3rd ed. New York: McGraw-Hill Book Company, 1986:543-9.
33 . Wilmore J. Sensible fitness. Champaign: Human K i-netics Publishers, 1986: 44-50.
34 . Mayer J, Marshall NB, Vitale JJ , et al. Exercise, food
in take and body weight in normal rats and geneticallyobese adult mice. Am J Physiol 1954; 177:544-8.35. Woo R, Garrow JS , Pi-Sunyer FX . Effect of exercise on
spontaneous calorie intake in obesity. Am J Clin Nutr1982; 36: 470-7.
36. Gwinup G, Chelvam R,Steinberg T. Thickness of sub-cutaneous fat and activity of underlying muscles. A nnIntern Med 1971; 74:408-11.
37 . Katch FI, Clarkson PM, McBride T, et al. Preferentialeffects of abdominal exercise training on regional adiposecell size [Abstract]. Med Sci Sports Exerc 1980; 12: 96.