Most IT people have trouble staying fit. I am also in upper limit of normal weight but I found some helpful apps recenlty.
I believe that biggest problem is finding time to stay fit. Going to gym after works takes better part of the evening and you have to do it like 3 times a week which is not easy.
Firstly the famous 7 minute workout that some scientist say is as good as full scale training if you do it every day. Read more about it from http://well.blogs.nytimes.com/2013/05/09/the-scientific-7-minute-workout/
I have tried it for 2 months ca 5 times a week and I can see clear results already After first month I was able to do 50% more pushups. In 2 minutes I used to do around 45 and it went up to 70. I can see distintct muscles building from the mirror. I also feel not getting out of breath so easily. So this means it really works and makes you stronger. The app I use is https://play.google.com/store/apps/details?id=com.popularapp.sevenmins&hl=en
Second app for staying healthy is Ingress. It is invite only augmented reality actiongame where you have to move around in the city from one portal to another and take these under you control. Usually I run for 50-100 meters from one portal to another, do actions on phone that is needed and run to another. Its is great hobby after the lunch for 10-15 minutes and while commuting between office and home.
It is amazing because the gamification moment helps you motivate to find some more minutes (or hours) to walk or run. Download it from https://play.google.com/store/apps/details?id=com.nianticproject.ingress&hl=en
Thirdly I have been able to lose some weight. There is nothing fancy here, just plain spending calories. In the summer I went to work and back with bicycle, I did some 30-40km trips with pulse in range of 130-140. This lasted 1,5h and used around 1800kcal. Considering that daily normal calorie intake is around 2500kcal then 3 times bicycling a week I lost around 5kg in 2 months. Unfortunately I had to make a pause because of knee injuryand then winter came with no daylight so there is big risk of getting killed in traffic. However same result can be achieved by same time and same pulse by walking, running, stairs climbing etc. App used is Endomondo https://play.google.com/store/apps/details?id=com.endomondo.android&hl=en
How are your experience with getting fit apps? Please write to comments.