Short- and long-term effects of hypocaloric diets containing proteins of different sources on plasma lipids and apoproteins of obese subjects

The influence of caloric restriction on lipid profile is controversial. This study was designed to evaluate the influence of dietary proteins from different sources on lipoprotein levels in obese subjects during a period of very low-caloric diet followed by 60 days of hypocaloric diet. The subjects were 24 obese patients aged 25-42 of at least 50% above ideal weight. The patients were separated into two groups and received for 15 days 375 kcal/day on the assumption that commercial textured preparations contained the same amount of proteins, respectively, as casein (group A) or soy protein (group B). Then the very low-caloric diet of the two groups was integrated with 425 kcal/day for 60 days. Body weight reduction was equivalent in the two groups. Total plasma cholesterol decreased significantly in both groups after the two periods of diet, but the percent variations were always significantly higher in the group B than in A. Total plasma triglycerides reduced significantly only in the group B. Very low-density lipoprotein (VLDL) and low-density lipoprotein (LDL) cholesterol behaved as total cholesterol in the two groups. High-density lipoprotein (HDL) cholesterol diminished significantly only after the 15 days of very low-caloric diet in group B, while it decreased throughout the diet in group A. The decrease of HDL cholesterol was mainly due to the HDL2 subfraction. The results of our study show that the substitution of soy protein for casein can be of benefit in those patients who need a long-term hypocaloric diet.