For the World Health Organization and most nutritionists, one obvious answer is sugars. But the United States government and American food companies seem to have a different idea.

Last year, WHO and another United Nations agency, the Food and Agriculture Organization, issued a report called "The Expert Consultation on Diet, Nutrition and the Prevention of Chronic Diseases." It suggested a strategy of dietary changes for individuals, including limits on sugar consumption, as well as policies that might make it easier for people to eat more healthfully.

The U.S. Department of Health and Human Services should have applauded, but instead it produced a 28-page, line-by-line critique centered on, of all things, what it called the report's lack of transparency in the scientific and peer-review process.

Although the department framed the critique as a principled defense of scientific integrity, much evidence argues for another interpretation - blatant pandering to American food companies that produce much of the world's high-calorie, high-profit sodas and snacks, especially the makers of sugars, the main ingredients in many of these products.

The critique was sent to the World Health Organization in the hope that its executive board would reject its report when it met this week. Instead, the board decided to forward the strategy to its full membership for a vote in May, but, under pressure from some member states, it gave dissenters an extra month to comment before a final draft is issued. If accepted in May, the strategy won't be binding, but it would provide guidelines to countries seeking to reduce obesity.

To understand the significance of this battle, it is crucial to know that Americans are not alone in gaining weight. Obesity is now a global epidemic, with the International Obesity Task Force estimating that one billion people are overweight or obese.

In all but the poorest countries, obesity and its consequences, such as rising rates of heart disease and diabetes, are overtaking malnutrition as major health problems. Modern society, with its overabundance of high-calorie food, makes healthful eating difficult.

That the food industry is disputing the World Health Organization's science is all the more astonishing because the report is notable for the stunning banality of its dietary recommendations: Eat more fruits and vegetables, and limit intake of foods high in fats and sugars. Such recommendations are thoroughly supported by both science and common sense.

Understandably, industry lobbyists are uneasy about calls to cut consumption of sugars. One trade group, the Sugar Association, demanded that WHO conduct another scientific review. It also vowed to use "every avenue available to expose the dubious nature" of the report, including asking members of Congress to challenge the United States' $406 million in contributions to WHO.

When food industry executives or government officials complain about unsound science, self-interest is generally at work. Threatened by the conclusions of the WHO report, food companies and their government friends try to pick apart the science and delay action, just as the cigarette industry did for many years.

Senators Larry Craig and John Breaux, co-chairmen of the Senate Sweetener Caucus, asked the health and human services secretary, Tommy Thompson, to call on WHO to "cease further promotion" of the report, while trade associations for the sugar, corn refining and snack food industries questioned the report's legitimacy and asked for Thompson's personal intervention. They got it.

By making its position on WHO indistinguishable from that of the food industry, the Bush administration undermines the efforts of more forward-thinking food companies and threatens public health.

The administration's actions underscore the need for government to create a wall between itself and the food industry when establishing public health policy. It's time to stop trading calories for dollars.