Vicious cycles of obesity: a game of biological and social dynamics

Exces­sive weight affects almost half of the French pop­u­la­tion and on a glob­al lev­el obe­si­ty fig­ures have tripled over the last 40 years¹. In France, the fight against obe­si­ty began more than two decades ago with the first Nation­al Nutri­tion and Health Plan (PNNS), the fourth part of which was launched in 2019. A nation­al fight that is jus­ti­fied because obe­si­ty is not an ordi­nary dis­ease. Although we might tend to think that the increase in obe­si­ty is sole­ly the result of mod­ern diets and a seden­tary lifestyle, sci­ence is now show­ing us that there are more bio­log­i­cal and soci­o­log­i­cal fac­tors than pre­vi­ous­ly thought. 

From biol­o­gy to soci­ol­o­gy, researchers work­ing on the issue are fair­ly unan­i­mous on this fact: there is not one, but sev­er­al obe­si­ties. From a bio­log­i­cal point of view, it seems to have tak­en a long time to affirm, “ini­tial­ly, genet­ic epi­demi­o­log­i­cal mod­els, [with­out genome screen­ing], sug­gest­ed that 40–70% of the vari­a­tion in cor­pu­lence on a pop­u­la­tion scale could be attrib­ut­able to genet­ic fac­tors”, recalls Karine Clé­ment, pro­fes­sor and hos­pi­tal prac­ti­tion­er at the Pitié-Salpêtrière hos­pi­tal and direc­tor of the Inserm Nutri­Omique lab­o­ra­to­ry. “With the dis­cov­ery of mono­genic obe­si­ty, research has shown that cer­tain forms of obe­si­ty are caused by genet­ic muta­tions that alter cer­tain phys­i­o­log­i­cal mechanisms.”

How­ev­er, these mono­genic forms are rare. They rep­re­sent only a small num­ber of cas­es com­pared to the grow­ing inci­dence of obe­si­ty. In con­trast, poly­genic forms high­light the extra­or­di­nary com­plex­i­ty of obe­si­ty with asso­ci­at­ed genet­ic vari­ants present through­out the human body. Called “com­mon obe­si­ty”, the lat­ter is due to degrees of sus­cep­ti­bil­i­ty expressed through hun­dreds of gene vari­ants and a very impor­tant envi­ron­men­tal component.

Mono­genic forms are rare, they rep­re­sent only a small num­ber of cas­es com­pared to the grow­ing preva­lence of obesity. 

“These poly­genic forms are not sole­ly respon­si­ble for obe­si­ty,” explains the spe­cial­ist. These are forms in which the envi­ron­ment plays a pre­dom­i­nant role. In oth­er words, there are peo­ple in the pop­u­la­tion who are more like­ly than oth­ers – genet­i­cal­ly – to be over­weight when faced with the same diet and behav­iour²³. In addi­tion, there are cog­ni­tive fac­tors, such as cog­ni­tive restric­tion [the atti­tude of peo­ple who delib­er­ate­ly lim­it their food intake in order to lose weight or to avoid gain­ing weight] or the abil­i­ty to eval­u­ate food por­tions accord­ing to their needs. 

Soci­ol­o­gy con­sid­ers the same axiom as the nat­ur­al sci­ences, name­ly that obe­si­ty is ulti­mate­ly the result of ener­gy intake exceed­ing expen­di­ture. But it also adds dif­fer­ent types of obe­si­ty depend­ing on the asso­ci­at­ed social fac­tors. Jean-Pierre Poulain, pro­fes­sor of soci­ol­o­gy at the Uni­ver­si­ty of Toulouse, a spe­cial­ist in issues relat­ing to the social and cul­tur­al dimen­sions of human nutri­tion and author of the book Soci­ol­o­gy of Obe­si­ty, dis­tin­guish­es three main types of obe­si­ty, “pre­car­i­ous­ness, migra­tion and exces­sive pres­sure of aes­thet­ic ideals.”

These dis­tinc­tions help to under­stand the dif­fer­ent social dynam­ics and tra­jec­to­ries asso­ci­at­ed with obe­si­ty. “We often hear that obe­si­ty is over-rep­re­sent­ed among the work­ing class­es,” says Jean-Pierre Poulain. “Mak­ing this dis­tinc­tion is essen­tial if we are to hope for effec­tive pre­ven­tion mod­els. To illus­trate this point, we can use the Nutri­alis sur­vey which high­lights these qual­i­ta­tive dif­fer­ences in pre­car­i­ous­ness using quan­ti­ta­tive data. The preva­lence of obe­si­ty among peo­ple in pre­car­i­ous sit­u­a­tions is 8%, and it is 14% among peo­ple whose lives are deteriorating”. 

From the point of view of both dis­ci­plines, obe­si­ty is sus­tained by feed­back loops. In biol­o­gy, it is the accu­mu­la­tion of adi­pose tis­sue that main­tains obe­si­ty. “When you reach a cer­tain lev­el of obe­si­ty, fat mobil­i­sa­tion becomes dif­fi­cult. In a sit­u­a­tion where we nor­mal­ly have to metabolise lipids with, for exam­ple, phys­i­cal activ­i­ty, the hor­mon­al and bio­log­i­cal sys­tems that allow the process to take place cor­rect­ly are altered.” Karine Clé­ment insists that the accu­mu­la­tion of adi­pose tis­sue hin­ders fat loss. As such, it is easy to under­stand the vicious cycle that sets in and makes obe­si­ty a sys­temic dis­ease that is extreme­ly dif­fi­cult to treat.

In soci­ol­o­gy, researchers are look­ing at the dou­ble chain of causal­i­ty relat­ed to stig­ma­ti­sa­tion and the rep­re­sen­ta­tions that we col­lec­tive­ly have of an obese per­son. If pre­car­i­ty is asso­ci­at­ed with obe­si­ty, the sit­u­a­tion of obe­si­ty will also act on this pre­car­i­ty by form­ing a dou­ble chain of causal­i­ty. “An obese per­son has less access to uni­ver­si­ty, has a more dif­fi­cult school career, has dif­fi­cul­ty get­ting job inter­views, is dis­crim­i­nat­ed against at work, etc.”, illus­trates Jean-Pierre Poulain. Among peo­ple with few or no qual­i­fi­ca­tions, 14.3% are obese and 33.5% are over­weight, com­pared with bare­ly 5% obese and 19% over­weight among peo­ple with qual­i­fi­ca­tions⁴.

From the bio­log­i­cal to the soci­o­log­i­cal, obe­si­ty thus becomes a self-per­pet­u­at­ing med­ical and social patho­log­i­cal sit­u­a­tion. And if med­ical research can hope to pro­vide some solu­tions, it would seem that an impor­tant issue is the stig­ma­ti­sa­tion of obese peo­ple. “Stick a label on some­one that will become the main sta­tus of the per­son con­cerned and all oth­er char­ac­ter­is­tics fade away,” explains Jean-Pierre Poulain. “This stage marks the cleav­age between this per­son and peo­ple con­sid­ered ‘nor­mal’. We are in a phase of dis­crim­i­na­tion that is not yet stig­ma­ti­sa­tion – but almost.”

“Sup­port­ed by ratio­nal choice the­o­ries, an obese per­son will be seen as some­one who can­not con­trol them­selves with food. From there, we can then ask whether they know how to con­trol them­selves in oth­er areas of their lives and whether they are trust­wor­thy in gen­er­al, sim­ply because of their appear­ance,” says Jean-Pierre Poulain. In oth­er words, obese peo­ple are con­sid­ered to be entire­ly respon­si­ble for their sit­u­a­tion, where­as their share of respon­si­bil­i­ty is like­ly much small­er than that. 

Karine Clé­ment agrees. “To uphold that obese peo­ple are respon­si­ble for their sit­u­a­tion and that eat­ing less is a mat­ter of choice is a com­plete­ly obso­lete view in nat­ur­al sci­ence,” she says. “They have extreme­ly lim­it­ed scope with regard to genet­ic, phys­i­o­log­i­cal and cog­ni­tive fac­tors and the envi­ron­ment in which they live.”

As a result, biol­o­gy and soci­ol­o­gy agree that obese peo­ple can­not be held sole­ly respon­si­ble for their sit­u­a­tion. On the one hand, genet­ics, feed­back process­es and the obe­so­genic envi­ron­ment make the per­son obese, and on the oth­er hand, devel­op­men­tal tra­jec­to­ries, the dou­ble causal chain of precarity/stigma and the pres­sure of val­ue sys­tems to adopt solu­tions that aggra­vate the prob­lem make the obese per­son a pris­on­er of their situation.

The fight against obe­si­ty is there­fore being waged on two fronts. On the one hand, the med­ical sci­ences and the era of block­buster drugs have dreamed of the mol­e­cule that would make obe­si­ty a bad mem­o­ry. Karine Clé­ment and Jean-Pierre Poulain both take a crit­i­cal look at this moment in the his­to­ry of the fight against obe­si­ty. The uni­ver­si­ty pro­fes­sor and hos­pi­tal prac­ti­tion­er remem­ber it as a “hard blow to the field”, while the soci­ol­o­gy pro­fes­sor points to the ampli­fi­ca­tion of the prob­lem by the phar­ma­ceu­ti­cal indus­try, which thought it had the per­fect solu­tion. The abject fail­ure of drugs with a reduc­tive view of the dis­ease has high­light­ed the need for a more indi­vid­u­alised approach to obe­si­ty. This is what research is now pursuing. 

“What­ev­er we do in the field of obe­si­ty man­age­ment, from hygiene and dietary rules to phar­ma­col­o­gy and even surgery, there are con­sid­er­able vari­abil­i­ties in the response to these treat­ments and the chal­lenge of research is to detect these vari­ables in order to improve the man­age­ment of obe­si­ty,” explains Karine Clément.

Final­ly, pre­ven­tion and pub­lic health mes­sages have focused on the behav­iour of indi­vid­u­als, often con­sid­er­ing them as the homo eco­nom­i­cus of ratio­nal choice the­o­ry in most coun­tries of the world⁵. The effec­tive­ness of these meth­ods clear­ly leaves much to be desired and points to the need for pub­lic health to move away from dis­em­bod­ied pro­mo­tion of what should be done and instead address the social caus­es of obe­si­ty, name­ly pre­car­i­ty and the val­ue sys­tems asso­ci­at­ed with thin­ness that are major deter­mi­nants of the way we eat and move. The aim is to improve the mate­r­i­al con­di­tions of indi­vid­u­als while dis­cred­it­ing the dis­course that makes thin­ness a guar­an­tee of health. Every­thing remains to be done.

Julien Hernandez