The rowing machine is by far the best gym machine for slimming. Both because of the calories burned in rowing and because of the muscles you exercise and its low impact. In an average session you can burn about 800 calories in one hour. It's a great way to lose weight even if you can't devote much time to training.
You can optimise your training on the rowing machine to increase energy expenditure in each work session. For example by alternating speed and intensity at 30-second intervals or with other interval training. It is an ideal machine for training, obtaining a great performance in the burning of calories and fats as well as in bodybuilding.