The French, he pointed out, had a lower rate of heart disease, a higher life expectancy and a far lower rate of obesity than Americans - and no complexes about fat-free this or salt-free that. What is more, they managed this without any government agencies compiling food "pyramids" telling them what they should eat more or less of (meat at the apex, grains at the broad base), and without the "five servings" rule. This is the US government's advice - widely ignored unless "fries" (chips) are counted as vegetables - that says every adult should consume at least five servings of fruit and vegetables a day.
Nor was Prof Rozin alone in his concern. At a Washington symposium on dietary behaviour titled "Why we choose the foods we eat", sponsored by the US Department of Agriculture, one specialist after another lamented Americans' unhealthy eating habits, inveighing against everything from the sedentary lifestyle, fostered by the car, TV and the internet, to the culture of excess, as manifested in gargantuan restaurant portion sizes and supermarket packaging.
The composition of US meals also came in for criticism: the tendency to use processed food, the decline of the family meal, the increasing resort to fast food, and the gallons of "soda pop" with which it is all washed down. Repeatedly, the nutritionists noted the replacement of the dreaded fat by equally calorific sugar in supposedly healthy low-fat foods.
The potential harm of fat, they agreed, was one message that had been absorbed - so much so that in the past decade the whole diet had been skewed. Prof Rozin produced a survey of college students showing that 30 per cent believed that eating one teaspoonful of ice-cream was more harmful than consuming a pound of cottage cheese. He also showed slides demonstrating the difference between a typical American supermarket shelf, where there was scarcely a pot of plain yoghurt in sight, and a French one, where fat-free or low-fat varieties took up only a small part of the shelf. The question for the assembled experts was: what could, and should, be done?
That a solution had to be found was taken as read. Just days before, the Journal of the American Medical Association (Jama) had published a series of studies tracking what one of the authors said was a veritable "epidemic" of obesity engulfing the US. In 1998, 37 states had an obesity rate of more than 15 per cent, compared with only four in 1991. Jama suggested that substantial changes in diet and lifestyle might be the only remedy.
Hard on the heels of that study came another rebuke from a quite different source. The doyenne of French cooking in the US, Julia Child, inaugurated a new 22-part TV series and an accompanying book by telling the New Yorker magazine that Americans had ruined their diet with their fanatical fear of fat. Now 87, and in robust health, Ms Child said their concern about getting fat had led them to conclude that "butter was dangerous, and eggs were dangerous and red meat was dangerous ... the press reported it and people believed it". The beef industry, she said, had been "ruined". "You can't get a marbled steak, even in top restaurants. The flavour and texture have gone out of the meat."
Ms Child probably has more chance of convincing fat-fearing Americans to change their habits through her forthcoming television series than do the experts. Their mood is grim, largely because they can see no solution acceptable to their compatriots short of a fail-safe stay-slim drug.
The diet specialists insist, probably correctly, that a majority of Americans know what they should be eating. The problem is that either they are too lazy to eat the right stuff or choose not to. "Is it possible," asked Prof Adam Drewnowski of the University of Washington in a final, wistful, contribution, "that French food affects a different area of the brain?" He cannot be the only American to hope that were true.