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