Megan Rosenfeld's rollicking history of fat [Style, Oct. 12] said: "Over the last 20 years we've reduced fat consumption, as they told us to, and physical activity, which they didn't. And obesity has gone up and up. Where does that leave us?"

She's correct that the public has reduced its intake of fat as a proportion of its food eaten. The trouble is that people are overeating to the extent that their overall fat intake has gone up even though fat is a smaller portion of their diet.

Further, many fat-free prepared foods taste good because high-calorie ingredients -- often sugar -- have been added. Fat-free food labels encourage people to ease off their dieting, and many people actually boost their food intake.

The "they" in the quotation from Ms. Rosenfeld probably refers to doctors and other disease-prevention educators. They have been telling us for years to exercise more, but many groups don't get the message. High school students, for example, are not exercising as much as they once did.

Ms. Rosenfeld asked, "Where does that leave us?" The answer is that it leaves us too fat, but not because we weren't told better.

NATAN POLSTER

Washington

The writer is editor and publisher of a newsletter covering heart, lung and blood research policy.