Pregnant guinea pigs were fed one of three diets: a control low-fat diet or a high-fat diet containing maize oil or beef tallow. Offspring were reared on the same diets as their mothers. At 12 weeks of age some animals were killed; others had their food intake restricted for 2 weeks and were then killed. Body weight, weight of various adipose tissue depots and size and number of fat cells were measured. All adipose depots decreased in weight during food restriction and fat cell size was reduced. Perirenal adipose tissue lost the greatest amount of weight and the gonadal depot the least. Fat cell number in females was unaffected by food restriction, whereas in males the number of observable fat cells decreased in the perirenal depot. Previous diet influenced the amount of body weight lost during food restriction. Animals fed beef tallow lost less weight than those fed maize oil. Possible reasons are discussed.

Pregnant guinea pigs were fed one of three diets: a commercial low-fat diet, or a high-fat diet containing maize oil or beef dripping. The young were killed at birth and the fatty acid composition of the lipids of the liver, plasma, adipose tissue, quadriceps muscle and red cell membranes was determined. Compared with those fed the commercial diet the tissues of the young of mothers fed maize oil had an increased percentage of linoleic acid whereas in those of the young of mothers fed beef dripping, the percentage of oleic acid was significantly higher. These changes occurred both in the triglycerides and in the membrane phospholipids (with the exception of sphingomyelins) of all tissues examined. These results demonstrate that the fatty acid composition of the tissue lipids of the newborn guinea pig can be influenced by the fatty acid composition of the maternal diet. Changes in the fatty acid composition of membrane phospholipids can be as great as those in storage lipids. This raises the question of long-term physiological significance for the animal.