The amount of conjugated linoleic acid (CLA) in the American diet has been lowered due to changes in the way we eat and in how farmers are raising their cattle. This can be seen as a contradiction: we are consuming less CLA, but we are also seeing a large increase in obesity.
Over the last 30 years, people worldwide have made a fundamental
change in the foods they eat. In an effort to guard against the negative
effects of heavy fat intake, people now eat significantly less beef and
dairy fats than they did just a few years ago. Despite all of this,
people are steadily gaining weight. In the United States alone, the
number of Americans who are at least 20 pounds overweight has grown from
25% in 1985 to more than 34% today.
People only get CLA from the foods they eat. CLA is found in a variety
of foods in very small amounts; beef and dairy fats contain the largest
quantities. When cattle eat grass, which is rich in linoleic acid, their
digestive tract converts the linoleic acid into conjugated linoleic
acid (CLA), a different molecule.



