ABSTRACT: some parameters of biological and biochemical of rats with low weight as affected by three protein sources (soybean protein, whey protein and meat protein) combined with chocolate, coconut, oat, and glucose syrup were studied. Twenty-four adult male albino rats were divided into 4 groups, their weight was an average 80±5g, there was one group kept as a control group, and the other three groups were given daily tested combined at the level 10% for 4 weeks. Body weight gain (BWG), feed intake (FI), feed efficiency ratio (FER), liver enzymes (ALT and AST), lipid profile (HDL-c, LDL-c and VLDL-c) and thyroid hormones (T3, T4 and TSH), were estimated. Results showed that body weight gain was markedly increased (P ≤ 0.05) especially in the group (4) fed on combined which contained meat protein, oat, chocolate, and glucose syrup followed by group (3) fed on whey protein, oat, chocolate, and glucose syrup combined when compared to control group. Meat protein combined caused significantly (P ≤ 0.05) increasing total cholesterol, triglycerides, low density lipoprotein cholesterol (LDL-c), very low density lipoprotein cholesterol (VLDL-c), mean levels and increased activity of aspartate aminotransferases (AST) and alanine aminotransferases (ALT) enzymes while soybean protein and whey protein combined caused significantly (P ≤ 0.05) decreased the above parameters as compared to group (4) and their mean values near to control group. From that, this study recommended that intake of the whey protein and soybean protein had good effect on the biological and biochemical of rats with low weight so, it may be useful for improving the low weight.