The activity and mRNA concentrations of two lipogenic enzymes, fatty‐acid synthase and acetyl‐CoA carboxylase were measured in the liver and white adipose tissue of rats weaned to a carbohydrate‐rich diet containing either long‐chain or medium‐chain fatty acids, and compared to those of rats weaned on a diet containing less than 1% (total energy) fat (high‐carbohydrate diet). In the liver, the diet containing long‐chain fatty acids inhibited the increase of both lipogenic‐enzyme mRNA concentrations and activities seen at weaning on the high‐carbohydrate diet but did not prevent the decrease in phosphoenolpyruvate carboxykinase mRNA and activity. In contrast, the diet containing medium‐chain fatty acids induced a slower but finally similar increase in lipogenic‐enzyme mRNA concentrations and activities. In adipose tissue, a similar trend was observed, although the inhibitory effect of the diet containing long‐chain fatty acids was considerably less marked than in liver. It is concluded that medium‐chain and long‐chain fatty acids have not the same inhibitory potency of the gene expression of lipogenic enzymes, and that long‐chain fatty acids have a more marked effect in the liver.