I lost about 4 kilo's now being doing it for 28 days now.

Seems that Wii Fit is working! Gogo!

The strength training exercises on Wii Fit are not the fastest or most efficient way to build mass for someone like yourself who is extremely thin for your height. You're technically borderline "malnourished" with a BMI of 17.1

The best thing you could do is simply eat better. Quality proteins, whole grain carbs and unsaturated fats. Really, when you're that thin, virtually anything you eat will do so long as you eat enough consistently.

If you're trying to put on muscle fast, and are doing the appropriate amount of muscular strength exercises to build up, I'd recommend eating at least 1g of protein per lb of body weight every day. If you can't get that much through regular food (beef, fish, poultry, soy, dairy, etc.) you can always resort to supplementing with whey protein used by most bodybuilders.

As for what is the appropriate amount of MS exercise, for someone who is not actively doing strength exercises and hasn't been for an extended period of time (or has never done a dedicated strength training program), Wii Fit is actually not a bad program to start with since it eases you in very slowly. There is almost zero chance of injuring yourself doing these exercises unless you are completely uncoordinated or accident prone (accidental wii remote Chuckers qualify).

I did about an hour and a half of exercises on it (every exercise/activity available at least twice) during my initial trial and if you are already in reasonable shape, it just doesn't cut it for an intense workout that could be packed into a much shorter period of time. It's play, but it's active play.

The duration you are doing each of the typical exercises is simply too short initially. Additional reps open up the more you do the exercises, but there is no option to do multiple sets beyond re-doing the activity muliple times. I'm sure the idea is to allow for maximum variety, but anyone who has ever done serious MS training has never used a program that only required one set per exercise. Not if they expected solid results.

The Yoga exercises are too brief as well, much like the strength training exercises. Once is not enough for any of them, but it is still a good start.

You could do a more efficient, more intense MS workout just with basic crunches, dips, pull ups and various types of push ups (all body weight exercises) than could be done through Wii Fit. Without waiting for evaluations and the menus, you'd be done in much less time.

And time is a big factor with Wii Fit because I can't see most people using it for an hour a day, every day, which is almost how long it takes to do the recommended "30 tokens" a day for significant exercise. Of course anything is still better than nothing, and if Wii Fit makes activity entertaining enough that you'll stay with it, it will produce better results over time than an intense program that can result in injuries, or the simple lack of desire to stick with it.

Some of the aerobic exercises are pretty decent though. If you did the running in place (a poor man's tread mill, but more entertaining because of the reactive visuals) multiple sessions in a row on the long run option and the 6 minute sparring exercises multiple times in a row throwing real punches (as you would with a heavy bag not "Tae Bo punches") on a daily basis, you'd raise your metabolism considerably over time and lose weight.

Just as you cannot lose 4lbs of fat in 4 days, you can't lose 4lbs of muscle in 4 days either. Muscle simply does not atrophy that quickly, even in a zero G environment.

Body weight can fluctuate about 5lbs in a day, given the right circumstances (up to 7 according to Wii Fit), but most of that weight fluctuation is water, and the amount of food traveling through your GI tract. 

The easiest way to determine body water % (and water weight) is with a scale that measures body fat % and water % like a Tanita.

But even if you did a genuine max workout (like run a marathon) you can still calculate the amount of energy reserves you burned off and then figure out how much of the weight you lost during such a workout was due to water loss, even without such a scale. 

It takes 3600 calories worth of activity to burn off 1lb of fat. You have to run at a pretty decent pace to even burn off 1000 calories per hour to give you an idea of how much activity it would take to burn off 4lbs of straight fat.  

Increased metabolism due to sustained increases in activity levels however, will continue to burn more energy during sedentary periods, particularly with increased muscle mass. But this is not an effect you would expect to see after just a dozen or so moderate workouts. 

2.1kg in 5 days is insane.

Word of caution mafoo, spikes of weight loss always get compensated by spikes of weight gain. between 1 and 2 kg's A WEEK is a good target.

Then again, I have no idea the conditions in which you weighed yourself both times, so it might be normal (like if you originally weighed right after a meal).

Good job anyway, hope you have continue and sustained weight loss (obviously to the point of "healthy" and not beyond that).

And what about if i don't want lose weight?, i only want to do excersice without losing weight, Wii Fit worth it for me?

Wiifit is worth it if you want to loose, gain, or keep the same weight. That is, as long as you use it several times a week, even if for only 10 minutes each time to do a quick bmi measurement and balance test to see how you are doing, and then do your training elsewhere if you prefer.

Rather if wii fit is worth it is questionable (up to you) as you can easily do any of those exercises without the board.

I have done ok on it. Its been about 2 weeks, and lost 'around' 2-2.5kg. How much of it is due to WiiFit, or just "general awareness of my fitness" (i.e. eating less crap) I cannot tell. But its definitely working - now slightly less tubby for the wedding :)

Results are ONLY really valid over a long(er) period of time (2-4 weeks min I would say). Bodyweight & clothing fluctuations can make an easy 1-1.5kg difference within a day.

Then you would focus on strength training and mix in some yoga for additional work on your core and balance and go light on the aerobic training.

Truth be told, unless using the program and balance board motivates you to keep going (you enjoy using it/are having fun), there is no point at all in buying Wii Fit. It will only end up in the closet as is often the case with exercise equipment.