French women, the world’s biggest consumers of beauty products, have been given a reason to spend even more this summer with the first plausible evidence that slimming creams really work. We are not talking about miracles like the “slim pill”, the Holy Grail which has long been pursued by the pharmaceutical industry, but something more modest.

According to the National Institute for Consumer Protection (INC) in France, which carried out tests on 200 women, at least two brands of crèmes amincissantes succeed in their promise of trimming cellulite and flab from thighs.

The news was greeted as vindication by those who spend more than £50 million a year on creams and gels in a quest for minceur, the ideal of slim femininity imprinted more deeply in the psyche of French women than most others.

Three decades on from sexual liberation, les françaises remain powerfully attached to the canons of beauty that for centuries have been drummed into little girls and deemed de rigueur for self-respecting women. The modern Parisienne business executive will still “soigner son look” before dropping into the baker’s for a baguette while her British sister may be happy to shuffle in wearing a tracksuit.

It is not about submitting to male dictatorship, say French women, but rather about perfecting the pleasures of life. As far back as the Hundred Years’ War, English soldiers marvelled at the style of Frenchwomen just as do the tourists of 2004.

There is a downside to the natural chic of la française. The devotion to the feminine ideal allows men to keep up the patronising tone taken to women throughout French history. To take an example from Charles Baudelaire, the woman-mad 19th-century poet: “La femme ne sait pas separer l’âme du corps” (Woman knows not how to distinguish her soul from her body).”

One particular pursuit of the feminine ideal, so-called body sculpting products, had been long scorned by the experts as pie-in-the-sky, sold to a credulous public through mendacious advertising. The INC magazine, 60 Millions de Consommateurs, noted: “We wanted to see if things had changed and there was a surprise. Among the 10 products that we tested, two enabled our volunteers to lose up to two centimetres around their thighs in 14 days. Three others showed a certain effectiveness after four weeks.”

The two top-scoring creams were L’Oréal’s Plénitude Perfect Slim and Elancyl’s Concentré-Lissant Chrono-Actif, both available at Boots and pharmacies in the UK. The INC said the effects appeared temporary and cautioned consumers not to imagine that the sculpting creams made them lose weight. “The slimming effect is significant, but relatively little all the same,” says Christian de Thuin, a doctor of chemistry who conducted the tests.

So how do they do it? Both companies are coy about the formulae that shrink the dreaded capiton, the orange-peel bumps of cellulite (a French-invented term). However, they make no secret about the key ingredient. “The chief active ingredient in slimming creams is caffeine,” says Laurence Robbe-Tomine, of Elancyl. “They put it in all products in different concentrations. It is lipolitic, which means that it removes stored fat.”

A big factor in slimming creams is the excipient, the inert creams, which enable the active ingredients to penetrate the fat cells, says Robbe-Tomine. L’Oréal confirms this. Fabrice Laizé, a scientist who worked on Perfect Slim, says: “The secret of the cream’s effectiveness is its texture. It’s like the cuisine of a great chef. The same ingredients cooked differently do not always end up with the same flavour. The texture has to penetrate well and not too quickly so that it promotes massage while being applied.”

L’Oréal’s product also uses caffeine and concentrates on two actions: blocking the storage of fat and draining engorged tissue, says Laize. “We carry out clinical studies under outside medical supervision in the same way as the testing by 60 Millions de Consommateurs.”

The Bureau pour la Vérification de la Publicité (BVP), the state advertising watchdog, says it receives a huge number of complaints from disappointed customers about slimming creams and other products in the grey area between cosmetics and pharmaceutical products. It is hard to nail the offenders, however, because they skirt the law with clever language. “The advertisers don’t use the verb maigrir (to lose weight) but mincir (to get slim) which is more subtle,” says Joseph Besnainow, the director of the BVP. “They say that women who used this cream became slimmer but they do not say whether they also lived on French beans for a fortnight . The adverts do not say, ‘I will make you lose weight’ but ‘certain people have got slim with this cream’.”

Exaggerated claims also accompany the mountain of other pills and capsules that French women swallow in order to shape their legs, promote a tan, rejuvenate their skin, or even “improve the intestinal transit”. The sale of such “beauty” medicines, usually in pharmacies, has jumped by 30 per cent in the past year.

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