Aspects of Obesity

The topic of obesity could provide material for a series of symposia. Personal prejudice has largely determined the aspects chosen for discussion here, and these are intended to demonstrate features bearing on our understanding of the nature of this disorder, which, as is generally recognised, has such profound medical and social implications. Adiposity itself is less of a problem than the sequelae and complications which so commonly occur. The epidemiology of obesity will not be dealt with now, but a moment’s reflection on the morbidity and mortality associated with being overweight will suffice to emphasise the importance of even a single example such as diabetes mellitus. Copyright Royal Medical Society. All rights reserved. The copyright is retained by the author and the Royal Medical Society, except where explicitly otherwise stated. Scans have been produced by the Digital Imaging Unit at Edinburgh University Library. Res Medica is supported by the University of Edinburgh’s Journal Hosting Service: http://journals.ed.ac.uk ISSN: 2051-7580 (Online) ISSN: 0482-3206 (Print) Res Medica is published by the Royal Medical Society, 5/5 Bristo Square, Edinburgh, EH8 9AL Res Medica, Autumn 1964, 4(3): 7-12 doi: 10.2218/resmedica.v4i3.426


ASPECTS OF OBESITY
T h e topic of obesity could provide material for a series of symposia.Personal prejudice has largely determ ined the aspects chosen for discussion here, and these are intended to dem onstrate features bearing on our understand ing o f the nature of this disorder, w hich, as is generally recognised, has such profound m edical and social im plications.A diposity itself is less of a problem than the sequelae and com plications which so com m only occur.T h e epidem iology o f obesity w ill not be dealt with now, bu t a m om ent's reflection on the m orbidity and m ortality associated with being overweight will suffice to emphasise the im portance of even a single exam ple such as diabetes m ellitus.
In the studies to be discussed the necessity for a definition o f obesity naturally arises, but this need not be laboured.T ables relating height and weight, sex and age, arc readily available.T h ese tables usually provide a v e ra g e weights based on height.It m ight be argued that an average body w eight is less suitable than an ideal w eight as a basis for investigation and for planning treatm ent.T ables of average weights are based on actuarial analysis of previous experience, and these show a tendency for m ost people to put on w eight with advanc ing years.Such a concept appears to condone an increase in w eight that m ay indeed be harm ful.A t present it is im possible to assess the contribution m ade by coincident factors such as d im inishing physical activity to the disabili ties often attributed directly to obesity.
O th er standards have been proposed from tim e to tim e to distinguish the norm al from the obese, and these are usually based on m easurem ents or estim ates of the am ount of obese tissue in the individual.Som e o f these techniques arc as sim ple as m easuring the thick ness o f skin folds with a calliper in standard areas, while others are based on the volum e of distribution of deuterium oxide or tritiated water which will equilibrate with the total body water and from this the lean cell mass and thus by difference the am ount o f adipose tissue can be determ ined.W eigh in g under water w ill also provide an estim ate of body fat.T h e choice between these and other m ethods is not critical, however, for the purpose o f this paper.In studying obesity it is m ore profitable to select groups o f individuals w ho clearly transgress the bounds o f any norm al range, so that by any standard they arc clearly abnorm al.
W h e n confronted by an obese patient, and faced with the necessity o f advising treatm ent, two im m ediate problem s present them selves.Firstly, and as a m atter o f expediency, w hat advice should be offered?Secondly, w hy has the patient becom e obese?In seeking to rationalise the second question we m ay answer the first m ore effectively.
Fund am entally, it m ay be claim ed, the fat are overw eight because control of the balance between energy intake and ou tput is defective, and the balance remains positive too often for too long.From this prem ise it m ay be argued reasonably that the loss o f m e tabolic equilib rium could occur because the intake o f energy was in excess of needs, or alternatively, and even in addition, that the output o f energy was insufficient to deal with the load imposed on the intake side o f the equation.T h ese are really about the on ly assum ptions that can safely be m ade at present.
T h e contribution o f energy ou tput as a m echanism for m aintaining a steady w eight is difficult to study because o f the technical prob lem s involved, and particularly b ecause the in vestigation m ust be extended as far as possible in tim e in order to take account o f fluctuations that are constantly occurring.V ariations in the am ount of energy lost in the urine and stools can be discarded as factors of im portance in m ost cases.V ariations in the physical activity of the patient how ever certainly cannot be ig nored.E ven when it has been shown that the obese exert themselves less than those who remain thin, the problem remains w hether this econom y o f effort is cause or effect.O nly prospective studies would provide an adequate answer to this question and such an undertak ing m ay be well nigh im possible.Several workers, notably Stunkard, a psychiatrist in Philadelphia (C h irico and Stunkard, 1 960) and M ayer (Johnson, Burke and M ayer, 1956) in the D epartm ent of Public H ealth in Boston, have shown that on average the obese exert them selves less than do their m ore slender controls.T h is applies in children as well as in adults, and appears to affect girls m ore than boys.It m ay be noted however that the fat patient does m ore work than the lean in m ov ing the same distance, for the m ost obvious of reasons, nam ely that the bulk to be m oved is greater.
T h u s the conclusion stands that m any fat people spend less energy on kinetics than those who are thin, and they apparently fail to restrict their energy intake appropriately, and there fore becom e or remain obese.
Fo r 50 years or m ore, suggestions have been m ade that the norm al individual has a m eta bolic " bypass" denied to the obese, for burning off surplus energy, and that for this reason the fat man w ho eats m ore than his energy output would require w ill accum ulate adipose tissue, while the thin man w ith his " bypass" remains thin in spite of eating m ore than is necessary to m eet his strict requirem ents.T h is postu lated m echanism was described as " luxus konsum ption" by G ra fe (19 3 3) but it has never really been dem onstrated with conviction.In deed m ore evidence has been adduced against it than in its favour.
T w o further aspects o f the ou tput side of the energy equation should be m entioned here.T h e first of these is exem plified by a group of seven grossly obese patients w ho were studied m ost rigorously under hospital conditions, but in a general ward.T h e ir diets provided between 370 and 550 kcal.daily only and by encouraging them to take exercise until they were walking as m uch as ten m iles daily, these patients were able to dissipate sufficient energy to achieve negative energy balances to the ex tent o f 2500-3000 kcal.daily.As m ight be predicted they all lost very substantial am ounts of w eight in periods o f six weeks study, the 1 5 0 g. or 0 .33lb.M o st o f the points in Fig. 1 represent intervals o f one week.It w ill be noted that the fall in w eight tends to be step wise, and indeed at one stage fo r a period last ing several weeks she failed to lose any w eight at all, although adhering to the usual regimen.I n spite o f fluctuations of this type however, the overall loss o f w eight was steady through out.F o r a phase o f 8 m onths approxim ately, records were kept o f her m enstrual periods, and it will be seen again that abou t the tim e of onset o f her period, a sharp rise in w eight usually occurred, subsiding again thereafter with an appropriate increm ent in w eight loss, to resume the steady decline.
In Fig. 2 the daily w eight changes are shown that occurred in the interval follow ing her adm ission to hospital.T h e striking alterations in the rate of loss o f weight m ay easily be seen.From the point of view o f obese patients taking strict reducing diets, it is m ost im portant that they should be told w hat they m ay anticipate when dieting conscientiously.
Unless this is done they becom e disillusioned when the rapid initial loss of eight o f the type illustrated in Fig. 2 fails to continue, and thereafter abandon the very real effort involved in adhering to a regimen likely to produce consistent results.E ven m ore discouraging are the phases o f water retention also illustrated, when not only is loss o f w eight not continuing but gains in w eight are occurring, som etim es for several days in succession.Phases o f this type m ay persist for 10 -14 days or m ore, and unless the patient is constantly rem inded that this failure to lose w eight is tem porary only, that it is relatively com m on and w ill be succeeded by a com pen sating period with an increased rate o f weight loss, only the stupid or unnaturally stoical patient is likely to continue with dietary re strictions.
T h e m echanism responsible for the water retention accounting in turn for these rather anom alous changes in w eight has not yet been identified.
Studies by R ussell (1962) on sodium an d water excretion by obese patients on reducing diets strongly suggest that the surplus water accum ulated in the circum stances described is aecom panied by sufficient sodium to keep the additional water retained isotonic with extracellular fluid: from tim e to tim e the excess o f both is released and excreted.T h ere are grounds for suggesting that som ething sim ilar m ay happen when m ore generous diets providing up to 1000 kcal.daily are in use.In these circum stances, feeding a high carbo hydrate diet enhances water retention, a high fat intake on the other hand w ill prom ote a m ore rapid rate o f loss o f w eight for a few days, until a new equilibrium has been estab lished, and w eight loss w ill then continue predictably, depending on the energy balance.
Studies undertaken in a num ber o f centres bearing on the w eight reducing properties of a variety o f diets would indicate that when adhered to strictly, and excluding short term differences due to variations in water balance, the ultim ate rate o f loss o f w eight depends upon the caloric content o f the diet, and not upon the form in which these calories arc taken.
It should be added that w hile the energy content o f food is all im portant in m aintaining w eight at a constant level, the relative content of carbohydrate, protein and fat in the food eaten are probably of m inor im portance except to the extent that they affect the palatability of food and therefore the appetite o f the patient.In the longer term , however, the reverse w ould be true when the patient or subject has freedom o f access to food.T h e satiety value or appetite suppressing properties o f food m ust be o f the greatest im portance in determ ining when a person with free access to food w ill stop eating.O ur ignorance in this regard m ust largely be attributable to the form idable problem of dem onstrating in man w hat it is that stops him eating.W e know that in anim als hypothalam ic centres for eating and for satiety can be dem onstrated, and that exercise and tem perature,solitary confinem ent or group feeding, restricted periods of feeding or continuous access to food can all affect the issue quite profoundly.
T h e heat conserving properties o f a layer of subcutaneous fat and the effect on body tem perature was studied recently b y Q uaade (1963) in C openhagen.H e m easured the skin tem perature 011 the surface and the tem perature deep to the abdom inal layer of fat in groups o f obese, norm al and thin individuals, and showed that although the abdom inal tem pera ture in the fat man is slightly higher than in the thin, the skin tem perature is lower in the fat.T h e re are several possible explanations for these differences, but one reasonable interpictation would be that a heavier layer of surface fat is a m ore effective insulation against heat loss than a lighter covering of this type.Such a factor m ight contribute to the difficulty som e patients evidently have in dissipating surplus energy.
T h ere arc relatively few studies available of protein m etabolism in the obese and such as there are indicate that it m ay be norm al. T h is conclusion, however, should be accepted with reserve for the present.O ur own investigations suggest that obese patients lose little protein when taking severely restricted diets.
T h e obese also show an unusual resistance to the developm ent of ketosis: unusual in the sense that under dietary conditions and condi tions o f exercise, where the lean can be ex pected to excrete relatively large quantities of ketone bodies, the obese fail to do so.T h is too is characteristic o f the m aturity onset insulin resistant adult diabetic who is usually obese, but the protective factor possibly com mon to these two im portant conditions and responsible for their relative im m unity to ketosis remains to be shown.
O ne popular form o f practical therapeutics for the control of obesity is the use o f so-called appetite suppressants.In a society with access to unlim ited quantities of food, the problem for m any is when to stop eating.T h e clinical response to dietary restrictions is disappointing indeed, and there is a pressing need for som e m ethod of controlling appetite that does not depend only on the p atient's ability to exercise restraint at the tabic.T h e com m ercial possi bilities for appetite suppressive drugs have not been wasted on the m anufacturers, and there arc now 25 or m ore such preparations available in this country.M o st of these drugs are ep h edrine derivatives.Som e years ago m y col leagues and I attem pted to assess the value of two o f these drugs in the m anagem ent of obesity (H ampson et al., 1 960).D exam pheta m ine is widely used for this and other purposes, and it seemed a useful standard for com parison w ith a further drug on behalf of which at that tim e strong claims were being m ade for its efficacy as an appetite suppressant, nam ely phenm etrazine.Both were com pared against an inert placebo m ade o f chalk.
T h is clinical trial was arranged with out patients attending for dietary advice and they were all prescribed diets of approxim ately 1000 kcal.daily.T h e y were seen at intervals o f one week, and were given each treatm ent in turn for 3 periods each of 6 successive weeks duration, m aking 18 weeks in all.T h e order o f adm inistration of the 3 drugs was random ised, so as to elim inate as far as possible bias in favour of or against a regime because it cam e earlier or later in the period o f study.A nalysis showed that both the drugs were som ewhat m ore effective than the control tab lets, but that when the results were rearranged and com pared, irrespective o f the drug but rather between the order o f the 3 periods of treatm ent, m uch m ore was achieved in terms o f w eight reduction in the first period o f 6 weeks, than in either o f the two succeeding.
From this has emerged the view that this g roup o f drugs m ay have som e little help to offer, but only as a tem porary expedient.It is widely recognised that they m ust be regarded as drugs of addiction, and indeed our psychi atrist colleagues as well as others would be glad to see their use in the treatm ent o f obesity restricted or abolished altogether.A norectic drugs are never a substitute for the discipline of dieting, and the m arginal benefits they have to offer seldom ju stify their use.
Practising doctors are constantly preoccupied with the necessity for weight reduction and the difficulties surrounding this process.Prophy laxis is the essence of good treatm ent, and this applies to overnutrition just as it docs to so m any other disorders.A lthough so m uch attention has been paid to the process o f reduc ing weight, very little has been done to study the m echanism o f gaining w eight in the obese.Several years ago D r. Passmore and his col leagues (19 55) carried out energy balance studies on a group of thin young men who were overfed to capacity for a relatively brief period.In 1962 we (Passmore, Strong, Sw in dells and el D in , 1963) did the same for a pair of overweight young women who after a period of equilibration ate as m uch food as they could tolerate.In the course of 9 days overfeeding, largely with carbohydrate, they gained alm ost 3 kg. in weight, bu t in 6 days afterwards of alm ost com plete starvation, they not only lost the 3 kg.gained, but also alm ost 3 kg.further as well.
W h en the findings in the fat young women were com pared with the thin young m en, re markable differences were seen.T h ese studies suggest that there is som e substance in the frequent com plaints o f the obese about what they regard as a form o f biological injustice and what is sceptically disregarded by their physi cians, nam ely that when taking the same am ount of food as their thinner fellows, they gain weight, while the lean remain so.For a given excess of calories, the fat girls gained w eight m uch m ore dram atically than the thin m en, and indeed for com parable gains of weight, the excess of calories required by the thin men was m ore than twice that for the girls.F o r a gain of 2.5 kg. in weight, 20,000 kcal.each was needed by the thin m en, as com pared w ith 10,000 and 6,500 respectively by the two fat girls.
T h is procedure o f com paring the fat with the lean has led to studies in other aspects of m etabolism as w ell, in cludin g steroid horm one m etabolism .In recent years m any reports have appeared, m ainly concerned w ith adreno cortical function, and usually show ing that the excretion o f 17-hydroxycorticosteroids was g reater in the fat than in the lean.A nalysis of this data com m only indicates that the higher findings recorded are associated w ith, and pos sibly accounted for, b y the greater bulk o f the obese patient.T h e re is n o doubt that som e fat people go through a phase when their adrenocortical function is so vigorous as to create serious doubts regarding their clinical status, in the sense that they m ay be regarded as suffering from C u sh in g's syndrom e.
O ur own studies on this aspect o f obesity were concerned with oestrogen m etabolism in a group o f postm enopausal patients who ranged from the extrem es o f being underw eight to overw eight (Brow n and Strong, 1965).In jec tions o f oestradiol were given, that is one of the precursors o f all the oestrogen m etabolites to be found in the urine.T h e m ethods of assay available at the tim e m ade it possible to study the recovery of the adm inistered m aterial in the form o f two o f the m ajor m etabolites, nam ely oestriol and oestrone .It was found that the heavier the individual, the greater was the recovery o f adm inistered oestrogen as as oestriol, and the less as oestrone .T h is has interesting potential repercussions, since the biological activity o f these oestrogen m eta bolites varies very w idely, and som e o f the m etabolic and other abnorm alities to be found in the obese m ight be due to factors o f this type.
O ne further aspect o f our eating habits should be m entioned.S T U N K A R D has described w hat h e calls the " night-eating synd rom e" , im plying that this group o f obese patients cats little during the day, but in the evening and at night consum es large quantities of food.T h is perhaps is an extrem e exam ple o f a com m on h abit o f eating little or nothing of energy value at breakfast or lunch, bu t then taking a large evening m eal.
H ollifield and Parson (1962) have studied a com parable regim en in rats.O ne of two sim ilar groups o f rats was allowed free access to food at all times, while the other group was allowed to feed for two hours daily only.A fter a brief period when the " 2 hour feeders" lost som e weight, they rapidly caught up w ith and overtook their controls who had free and con stant access to food, as is usual with laboratory rats.T h e different rates o f gain in w eight were not accounted for by differences in food intake, and other studies o f fat m etabolism were thought to provide a tentative explanation.So far as is known the activity o f the anim als was not controlled, and one possibility would seem to be that the " 2 hour feeders" soon learned when it w ould be to their advantage to hunt for food, and that for the rest o f their tim e they conserved their energy in rest or sleep.
Studies of the m etabolism of labelled acetate by these anim als showed that the " 2 hour feeders" in the course o f seven days increased enorm ously their capacity to store the acetate as adipose tissue.T h e suggestion is therefore that adaptation to this unusual type o f feeding regimen radically altered the m etabolism of the anim als, so that they developed w hat m ay be described as a " storage phase" o f fat m eta bolism .
T h ese and m any other m etabolic differences that are em erging to distinguish the fat from the lean offer the prospect that out o f these investigations m ay arise better m ethods of m anaging disordered w eight control and so reduce an im portant source of m orbidity and m ortality in the better fed countries o f the world.
T h e wonder o f it is perhaps not so m uch that som e becom e obese, but rather that this fate overtakes so relatively few.

R E F E R E N C E S
J. A. STRONG, B.A., M.B., F.R.C.P.Ed., F.R.C.P. Physician, Western General Hospital Reader in Medicine, University of Edinburgh Ba se d on a Talk to the R o y a l M edical Society on Friday, January 31st, 19 64 Fig. I. Loss of weight by an obese patient on a diet providing 400 kcal daily.