Well I would say you have a

Well I would say you have a pretty good idea on what you want to do and are going about it right. Yes gaining muscle mass will boost metabolism and help you loose weight. I will give you a little food for thought though on this. Several studies have been done on this and in fact there was just another article on this in a medical study. Sorry I can’t quote it off hand would have to look it up when I get home later tonight. However here is a summary of it. Lifting weights compared to cardio.

Basically loosing weight or fat, mean you need a calorie deficit. You should get this deficit through exercise though by burning more calories rather than cutting them out of your diet, but sometimes diets need cut as well, depends on the person. So what gives you the biggest deficit, cardio or lifting weights. Well it depends on how you look at it my number aren’t exact but they are close. Say you do like an hour of cardio like aerobics, or bicycling, something like that you might burn 300-400 calories in that hour. Now say you do an hour of weight lifting, you may only burn 150 to 250 calories in that hour. So cardio wins right? Well again depends on how you look at it. Lets look at it over a 24 hour period. Lifting weights will increase metabolism and but more strain on your body for a longer period of time usually about 15 hours. So the person doing cardio for an hour in a 24 hour period might burn 2400 - 2500 calories in a 24 hours period, however the person weight lifting for an hour will burn 2700-2800 over a 24 hour period.

So really once you get to lifting weights you will start to burn the fat off and faster than doing cardio. There are a couple of rules of thumb about this. If you are trying to put muscle on never do more than 2 hours of cardio a week. You should also not do cardio on days you lift too unless you are cutting. Typically what most average people will do is lift 3 days a week and cardio 2 times a week. This gets a nice fat burn and tone going on and should fit right into your 5 days a week.

Me I absolutely hate cardio, but I do it 2 times a week and on workout days. I start my time at the gym with 10 minutes of cardio, which even on lifting days you should do only about that much. This gets your body warmed up and ready to lift. Then I stretch everything. Then I lift for hour, hour and half. Then I go back and do about 20 min of cardio. This gives me a hour of cardio a week. Which is good enough for me and when I do it, most people that body build and gain mass do not bother with cardio beyond warming up. When I really want to cut though then I do cardio in the morning every day I do not lift before breakfast. This starts a whole new metabolism burn. Then I change lifting to higher reps lower weights and a lot of super sets to build up more of a sweat and a burn. So to answer your quest just by starting to lift weights with your cardio you do now you will actually do both at the same time such as burn fat and gain muscle.

Comprehensive advice

Thanks very much for taking the time to explain the issues to me. Your suggestions will be a great help. I will certainly start doing more weights and less cardio, and hopefully I will see that weight coming off. I enjoy going to the gym, but this adds a new dimension. Thanks.

Also...

Increasing your muscle mass increases the resting metabolic rate. Not just for 15 hours after your previous workout, but constantly. This is due to the fact that muscles require energy to function even in low-strain everyday activities. More muscle -> more energy (glucosis, lipids) burned.

I'd recommend weight exercises affecting large muscle groups, for quickly adding muscle mass. Ex. bench presses and squats.

(Note: I see you want to lose 5 kg. If you do a lot of weight-lifting, your body weight might increase, or not decrease as fast as you'd like, but this is due to the increased muscle mass. Remember, it's the fat that you want to get rid off, not overall weight. So don't use the bathroom scales as the only indicator of how fit you are.)