The front page news today at the New York Times is that a low fat diet does not improve your health:
The largest study ever to ask whether a low-fat diet reduces the risk of getting cancer or heart disease has found that the diet has no effect.
The $415 million federal study involved nearly 49,000 women ages 50 to 79 who were followed for eight years. In the end, those assigned to a low-fat diet had the same rates of breast cancer, colon cancer, heart attacks and strokes as those who ate whatever they pleased, researchers are reporting today.
Now you need to synthesize this information with the news that it's healthy to be "overweight". The conclusion is that you should eat whatever you feel like and try to gain some weight, and this will help you live longer.
What you also get out of this is that the health authorities have been lying to you, giving you advice based on scanty information that turns out to be completely bogus.