Like all meats, lamb and chicken are rich in protein. While the two foods share this characteristic, other nutritional aspects of lamb and chicken differ. Lamb and chicken can both be components of a healthy diet, but you may find that one is better suited to your nutritional needs than the other. Note that cooking lamb or chicken in oil or other ingredients will alter the nutritional characteristics of the meat.
If you're trying to lose weight, choose chicken as the meat in your meal. One hundred g of cooked chicken breast contains 165 calories, while 100 g of lamb sirloin provides 204. While the chicken breast is lower in calories, you would have to eat the lamb frequently for it to adversely affect your weight loss. Switching from eating 100 g of lamb sirloin to 100 g of chicken breast daily would result in a reduction of 273 calories per week.
Both lamb and chicken are rich in protein, a nutrient your body uses to build and repair vital tissues and cells. Chicken is slightly higher in protein -- a 100 g chicken breast provides 31 g of protein, while 100 g of lamb sirloin contains 28 g. Consuming protein is vital for your health, and the recommended daily allowance is .8 g of protein for each kg of body weight. If you weigh 175 lbs., your target protein intake would be 63 g.
The difference in calories between lamb and chicken is largely from the difference in fat content. Lamb is higher in fat, with 9 g in an 100 g serving of sirloin, while 100 g of chicken breast contains just 3.6 g. Lamb also contains 3 g of saturated fat, compared to just 1 g in chicken breast. Too much saturated fat can increase your risk of cardiovascular disease, so the USDA suggests limiting saturated fat to no more than 10 percent of your total calories.
Both chicken and lamb can be suitable for reduced-carbohydrate diets, as both foods are carbohydrate-free. Carbohydrates are your body's primary energy source, but low-carbohydrate diets can help you lose weight if you reduce your total calorie intake as well.
Neither lamb nor chicken is a robust source of vitamins, although the latter contains high levels of choline, a B vitamin, and vitamin A. Lamb provides folate, a B vitamin, but little else.
While lamb and chicken aren't rich in vitamins, they do provide some minerals. Both foods are good sources of potassium, phosphorus, magnesium, iron and zinc. Lamb contains nearly five times the zinc chicken does.